Patent Grant
9561372
The present invention relates to neurostimulation treatment systems and associated devices, as well as methods of treatment, implantation and configuration of such treatment systems.
Treatments with implantable neurostimulation systems have become increasingly common in recent years. While such systems have shown promise in treating a number of conditions, effectiveness of treatment may vary considerably between patients. A number of factors may lead to the very different outcomes that patients experience, and viability of treatment can be difficult to determine before implantation. For example, stimulation systems often make use of an array of electrodes to treat one or more target nerve structures. The electrodes are often mounted together on a multi-electrode lead, and the lead implanted in tissue of the patient at a position that is intended to result in electrical coupling of the electrode to the target nerve structure, typically with at least a portion of the coupling being provided via intermediate tissues. Other approaches may also be employed, for example, with one or more electrodes attached to the skin overlying the target nerve structures, implanted in cuffs around a target nerve, or the like. Regardless, the physician will typically seek to establish an appropriate treatment protocol by varying the electrical stimulation that is applied to the electrodes.
Current stimulation electrode placement/implantation techniques and known treatment setting techniques suffer from significant disadvantages. The nerve tissue structures of different patients can be quite different, with the locations and branching of nerves that perform specific functions and/or enervate specific organs being challenging to accurately predict or identify. The electrical properties of the tissue structures surrounding a target nerve structure may also be quite different among different patients, and the neural response to stimulation may be markedly dissimilar, with an electrical stimulation pulse pattern, pulse width, frequency, and/or amplitude that is effective to affect a body function of one patient and potentially imposing significant discomfort or pain, or having limited effect, on another patient. Even in patients where implantation of a neurostimulation system provides effective treatment, frequent adjustments and changes to the stimulation protocol are often required before a suitable treatment program can be determined, often involving repeated office visits and significant discomfort for the patient before efficacy is achieved. While a number of complex and sophisticated lead structures and stimulation setting protocols have been implemented to seek to overcome these challenges, the variability in lead placement results, the clinician time to establish suitable stimulation signals, and the discomfort (and in cases the significant pain) that is imposed on the patient remain less than ideal. In addition, the lifetime and battery life of such devices is relatively short, such that implanted systems are routinely replaced every few years, which requires additional surgeries, patient discomfort, and significant costs to healthcare systems.
Furthermore, since the morphology of the nerve structures vary considerably between patients, placement and alignment of neurostimulation leads relative the targeted nerve structures can be difficult to control, which can lead to inconsistent placement, unpredictable results and widely varying patient outcomes. For these reasons, neurostimulation leads typically include multiple electrodes with the hope that at least one electrode or a pair of electrodes will be disposed in a location suitable for delivering neurostimulation. One drawback with this approach is that repeated office visits may be required to determine the appropriate electrodes to use and/or to arrive at a neurostimulation program that delivers effective treatment. Often, the number of usable neurostimulation programs may be limited by imprecise lead placement.
The tremendous benefits of these neural stimulation therapies have not yet been fully realized. Therefore, it is desirable to provide improved neurostimulation methods, systems and devices, as well as methods for implanting and configuring such neurostimulation systems for a particular patient or condition being treated. It would be particularly helpful to provide such systems and methods so as to improve ease of use by the physician in positioning and configuring the system, as well as improve patient comfort and alleviation of symptoms for the patient. It would further be desirable to improve ease and accuracy of lead placement as well as improve determination and availability of effective neurostimulation treatment programs.
The present invention generally relates to neurostimulation treatment systems and associated devices and methods, and in particular to improved integrated electromyography (EMG) clinician programmers which allow for more accurate and objective positioning, programming, and configuration of implantable electrode leads. The present invention has particular application to sacral nerve stimulation treatment systems configured to treat bladder and bowel dysfunctions. It will be appreciated however that the present invention may also be utilized for the treatment of pain or other indications, such as movement or affective disorders, as will be appreciated by one of skill in the art.
The integrated EMG clinician programmer of the present invention provides an objective and quantitative means by which to standardize placement and programming of implantable leads and neurostimulation electrodes, reducing the subjective assessment of patient sensory responses as well as surgical, programming, and re-programming time. Further, as the efficacy of treatment often relies on precise placement of the neurostimulation electrodes at target tissue locations and the consistent, repeatable delivery of neurostimulation therapy, using an objective EMG measurement can substantially improve the utility and success of treatment. Use of the integrated EMG clinician programmer to verify activation of motor responses can further improve the lead placement performance of less experienced operators and allow such physicians to perform lead placement with confidence and greater accuracy. Still further, automation of several steps or procedures associated with lead placement and programming with the integrated clinician programmer can further reduce the duration and complexity of the procedure and improve consistency of patient outcomes. For example, automation of electrode threshold determinations based on EMG responses can provide rapid feedback during lead placement and to identify optimal programming parameters.
An integrated electromyography (EMG) and signal generation clinician programmer may be coupled with an implantable temporary or permanent lead in a patient and at least one EMG sensing electrode minimally invasively positioned on a skin surface or within the patient. Generally, the integrated clinician programmer may comprise a portable housing, a signal/stimulation generator, an EMG signal processor/recorder, and a graphical user interface. The housing has an external surface and encloses circuitry at least partially disposed within the housing. The signal/stimulation generator may be disposed within the housing and configured to deliver test stimulation to a nerve tissue of the patient via a percutaneous needle or the implantable lead. The EMG signal processor may be disposed within the housing and configured to record a stimulation-induced EMG motor response for each test stimulation via the at least one pair of EMG sensing electrodes and a ground electrode. The graphical user interface at least partially comprises the external surface of the housing and has a touch screen display for direct user interaction or for use with a keyboard, mouse, or the like. As described in greater detail below, the integrated clinician programmer allows for controlled positioning or programming of the implantable lead based at least on the EMG record and provides the clinician with a convenient all-in-one setup via the EMG integrated clinician programmer.
The present invention provides improved methods for positioning of an implantable lead in a patient with an integrated EMG and stimulation clinician programmer. The integrated clinician programmer is coupled to the implantable lead, wherein the implantable lead comprises at least four electrodes, and to at least one pair of EMG sensing electrodes minimally invasively positioned on a skin surface or within the patient. The method comprises first delivering test stimulation at a stimulation amplitude level from the integrated clinician programmer to a nerve tissue of the patient with a principal or reference electrode of the implantable lead. Test stimulations are selected or adjusted in proportional increments to achieve a desired stimulation-induced EMG motor response. The method further includes test stimulations delivered at a same stimulation amplitude level for a same period of time sequentially to each of the four electrodes of the implantable lead. A stimulation-induced EMG motor response is recorded with the integrated clinician programmer for each test stimulation on each electrode of the implantable lead via the at least one EMG sensing electrode so as to facilitate initial positioning of the implantable lead at a target stimulation region.
The principal electrode is selected from the at least four electrodes of the implantable lead. For example, user input may be received related to selection of the principal electrode via a graphical user interface of the integrated clinician programmer. Additionally, user input related to adjustment of the stimulation amplitude level of the test stimulation for the principal electrode to achieve a desired stimulation-induced EMG motor response may be received via the graphical user interface of the integrated clinician programmer. For example, the user may adjust the stimulation amplitude of the test stimulation in increments in a range from about 0.05 mA to about 0.25 mA, wherein the test stimulation amplitude is generally less than 10 mA. The use of proportional increases in stimulation amplitude during test stimulation and/or programming effectively reduces the time required for such activities. The period of time for stimulation of each individual electrode comprises about 1 second and a sweeping cycle of the implantable lead is completed in less than or equal to about 5 seconds.
As discussed above, automation of certain aspects within the clinician programmer can further reduce the duration and complexity of the procedure and improve consistency of outcomes. For example, the principal electrode may be automatically selected based on a default condition by the integrated clinician programmer. Still further, the clinician programmer may be configured to automatically adjust the stimulation amplitude level of the test stimulation for the principal electrode until a desired stimulation-induced EMG motor response is detected to provide rapid feedback during initial lead placement. The desired EMG motor response may comprises a value associated with a minimum or maximum compound muscle action potential (CMAP). Automatically adjusting may comprise increasing the stimulation amplitude in increments of 0.05 mA for a test stimulation less than or equal to 1 mA, 0.1 mA for a test stimulation more than or equal to 1 mA and less than or equal to 2 mA, 0.2 mA for a test stimulation more than or equal to 2 mA and less than or equal to 3 mA, or 0.25 mA for a test stimulation more than or equal to 3 mA. The use of proportional increases in combination with the automated feature in stimulation amplitude adjusting during initial lead placement effectively reduces the time required for such activities. It will be appreciated that this automated feature may be easily terminated at any time and for any reason, patient safety or otherwise, by the user.
An EMG response value may be calculated by the integrated clinician programmer for each test stimulation delivered at a given stimulation amplitude level to each electrode based on a maximum EMG response amplitude (e.g., maximum CMAP peak, peak to peak, root mean square; up to 500 μVolts) associated with each electrode. Alternatively, the EMG response value may be calculated based on a maximum EMG response amplitude associated with each electrode which is normalized relative to an EMG response amplitude associated with the principal electrode (e.g., unitless R-value indicative of good (e.g., R≧0.5), not ideal (e.g., 0.25≦R≦0.5), or not acceptable positioning (e.g., R≦0.25)). Importantly, the EMG response value associated with each electrode may provide visual feedback to a user on how to laterally or axially position the implantable lead at the target stimulation region via the graphical user interface of the integrated clinician programmer. For example, the graphical user interface may include an implantable lead graphical element and the visual feedback comprises a color coding from at least three contrasting colors on a side of each associated electrode of the implantable lead graphical element. This visual feedback, in combination with fluoroscopy images, provides directional indication to the user on how to re-position the implantable lead with reference to the target nerve tissue. For example, whether the operator should advance the implantable lead distally along an insertion axis, retract the implantable lead proximally along the insertion axis, or steer the implantable lead along a lateral direction from the insertion axis so that a middle of the implantable lead is positioned at the target stimulation region. Alternatively or additionally, a relative distance or position of each electrode to the target stimulation region may be calculated based on the EMG response value associated with each electrode. The delivering test stimulations to each of the four electrodes of the implantable lead and recording steps after lead re-positioning may be repeated to confirm the calculated EMG response value for each electrode are within a desired similar value range (e.g., R-values=1), and/or the maximum EMG response amplitude for each electrode are within a desired robust response range (e.g., large CMAP) and the associated simulation amplitude for each electrode is within a desired reasonable stimulation range (e.g., lower stimulation amplitudes).
For sacral nerve stimulation treatment systems configured to treat bladder and bowel dysfunctions, the lead is configured to be inserted through a foramen of a sacrum and positioned in proximity of a sacral nerve root. For example, the target stimulation region may comprise an area the emergence of a sacral nerve from the sacral canal and it's convergence with other spinal nerves to form the sciatic nerve. A visual image of the recorded stimulation-induced EMG motor response during each test stimulation may be displayed on the graphical user interface of the integrated clinician programmer, wherein the visual image includes a waveform comprising a CMAP.
Methods further include validating and fine tuning lead placement by testing for a stimulation amplitude threshold for each electrode. For example, user input may be received related to an adjustment of the stimulation amplitude threshold of the test stimulation for each electrode in proportional increments to achieve a desired stimulation-induced EMG motor response at a minimum stimulation amplitude threshold via a graphical user interface of the integrated clinician programmer. The graphical user interface may further receive user input related to the recorded stimulation-induced EMG motor response (e.g., yes or no) or a sensory response from the patient (e.g., none, good, or bad) associated with the stimulation amplitude threshold for each electrode. For example, a negative sensory response from the patient associated with the stimulation amplitude threshold for a particular electrode may automatically override any positive or neutral feedback to the user on the stimulation amplitude threshold for that particular electrode. As discussed in greater detail below, user characterization of the presence or absence of motor and/or sensor responses may be of additional benefit in fine tuning lead placement.
Visual feedback may be displayed to the user on the stimulation amplitude threshold for each electrode, wherein the visual feedback comprises color coding from at least three contrasting colors on the graphical user interface. The graphical user interface may also include a visual indicator (e.g., color coding, symbols, shapes, empirical values) associated with each stimulation electrode and configured to indicate a status of the stimulation electrode (e.g., good if between 1-3 mA, bad if less than 0.5 mA or greater than 4 mA, ok if between 0.5-1 mA or 3-4 mA), an amplitude threshold value (e.g., up to 10 mA) of the stimulation electrode based on EMG record, an EMG value or status associated with the stimulation amplitude threshold value (e.g., up to 500 μVolts or unitless R-value indicative of good, not ideal, or not acceptable positioning), a sensory response status associated with the stimulation amplitude threshold value (e.g., none, good, bad), or an impedance status of the stimulation electrode (e.g., good if less than 3000 Ohms and greater than 50 Ohms and bad if greater than 3000 Ohms or less than 50 Ohms).
Optionally, as discussed above, the integrated clinician programmer may automatically adjust the stimulation amplitude threshold (e.g., slow proportional increases) of the test stimulation for each electrode to achieve a desired stimulation-induced EMG motor response at a minimum stimulation amplitude threshold. Of particular benefit, the integrated clinician programmer automatically stores, displays, and easily makes this characterization data available during the procedure, and is a far advancement over current clinical practices which employ paper notes and/or calculations in a clinician's head. Data for each test stimulation includes the incremental or proportional stimulation amplitude levels for each individual electrode of the at least four electrodes of the implantable lead, an associated EMG recording associated with the stimulation amplitude threshold, or user input related to the recorded stimulation-induced EMG motor response or a sensory response from the patient associated with the stimulation amplitude threshold.
The present invention provides further methods for improved positioning of an implantable lead in a patient in proximity of a sacral nerve root so as to treat bladder or bowel dysfunction. The implantable lead may comprise at least four stimulation electrodes arranged in a linear array along a length of the lead and be coupled to an integrated EMG and stimulation clinician programmer. The integrated clinician programmer may include connectors on the housing for coupling the EMG signal processor to first and second EMG sensing electrodes. EMG sensing electrodes are positionable on the medial border or sole of the foot to record EMG signals associated with plantar flexion of the big toe. The EMG sensing electrodes are positioned over and may record activity from the flexor hallucis brevis muscle and/or abductor hallucis muscle. The integrated clinician programmer may include connectors on the housing for coupling the EMG signal processor to a second pair of EMG sensing electrodes. The second pair of EMG sensing electrodes are positionable within the inner area of the patient buttocks near the anal sphincter, with positioning targeted over the levator ani muscles. These EMG sensing electrodes are positioned to record the anal bellows response of the patient, which represents activation of the levator ani muscles of the perineal musculature.
It will be appreciated that the EMG signal processor can also record a stimulation-induced EMG motor response associated with the big toe only or a stimulation-induced EMG motor response associated with the anal bellows only for each test stimulation. The test stimulation delivered by the signal generator comprises at least one electrical pulse below a muscle activation threshold and the EMG sensing electrodes detects stimulation of the nerve tissue. The integrated clinician programmer may further include an additional connector on the housing for coupling the signal generator to a foramen needle configured to identify or locate a target nerve prior to initial lead placement, as discussed in greater detail below.
The method comprises first delivering test stimulation at a plurality of stimulation amplitude levels from the integrated clinician programmer to the sacral nerve tissue of the patient with a principal electrode of the implantable lead, wherein the principal electrode is selected from the at least four electrodes of the implantable lead. Test stimulations are selected or adjusted in proportional increments to achieve a desired stimulation-induced EMG motor response. The method further includes test stimulations delivered at a same stimulation amplitude level for a same period of time sequentially to each of the four electrodes of the implantable lead. The integrated clinician programmer simultaneously records a first stimulation-induced EMG motor response associated with the big toe of the patient and a second stimulation-induced EMG motor response associated with the anal bellows of the patient for the test stimulations on each electrode of the implantable lead so as to provide for controlled positioning of the implantable lead at a target stimulation region.
As discussed above, user input may be received related to adjustment of the stimulation amplitude level of the test stimulation for the principal electrode in proportional increments to achieve a desired stimulation-induced EMG motor response via a graphical user interface of the integrated clinician programmer. Alternatively, the integrated clinician programmer may automatically adjust the stimulation amplitude level of the test stimulation for the principal electrode in proportional increments until a desired stimulation-induced EMG motor response is detected (e.g., increases rapidly until initial response is observed).
An EMG response value for each test stimulation delivered at a given stimulation amplitude level to each electrode may be calculated as discussed above. For example, it may be based on a maximum EMG response amplitude associated with each electrode which is normalized relative to an EMG response amplitude associated with the principal electrode. The EMG response value associated with each electrode provides visual feedback to a user on how to position the implantable lead at the target stimulation region within the patient.
Once the implantable lead is initially positioned, further input related to an adjustment of a stimulation amplitude threshold of the test stimulation for each electrode to achieve a desired stimulation-induced EMG motor response at a minimum stimulation amplitude threshold may be received via the graphical user interface. Additional user input related to the first or second recorded stimulation-induced EMG motor response or a sensory response from the patient associated with the stimulation amplitude threshold for each electrode may also be received. Again, the integrated clinician programmer may automatically adjust a stimulation amplitude threshold of the test stimulation for each electrode in proportional increments to achieve the desired stimulation-induced EMG motor response at a minimum stimulation amplitude threshold (e.g., increase slowly until the maximum magnitude EMG response is observed).
The integrated clinician programmer automatically stores or displays data for each test stimulation delivered at incremental or proportional stimulation amplitude levels for each individual electrode of at least four electrodes of the implantable lead and the associated EMG recording of the big toe and the anal bellows of the patient for each test stimulation. Method further include delivering the test stimulation to the sacral nerve tissue via a foramen needle and recording the stimulation-induced EMG motor response for each test stimulation delivered to the foramen needle so as to provide for initial positioning of the implantable lead at the target stimulation region. Similarly, user input may be received related to an adjustment of a stimulation amplitude level of the test stimulation for the foramen needle in proportional increments to achieve a desired stimulation-induced EMG motor response via the graphical user interface of the integrated clinician programmer. Optionally, automatic adjustments to the stimulation amplitude level of the test stimulation for the foramen needle may be made by the integrated clinician programmer until a desired stimulation-induced EMG motor response is detected.
The present invention provides methods for positioning an implantable lead in a patient with an integrated EMG and stimulation clinician programmer. The method comprises implanting a temporary or permanent lead having at least four electrodes in proximity of nerve tissue of a patient. At least one EMG sensing electrode is positioned on a skin surface or within the patient. The implantable lead is coupled to the integrated clinician programmer via a stimulation cable and the at least one EMG sensing electrode is also coupled to the integrated clinician programmer. A principal electrode is selected from the at least four electrodes of the implantable lead via a graphical user interface of the integrated clinician programmer and stimulated with a test stimulation via the integrated clinician programmer. A record of a stimulation-induced EMG motor response, as sensed by the at least one pair of EMG sensing electrodes, is displayed on the graphical user interface.
A stimulation amplitude of the test stimulation for the principal electrode is selected or adjusted in proportional increments to achieve a desired stimulation-induced EMG motor response via the graphical user interface. The method further includes sequentially stimulating the at least four electrodes of the implantable lead with the test stimulation at a same selected or adjusted stimulation amplitude level for a same period of time sequentially. Based at least on the EMG records, the implantable lead is re-positioned (e.g., advancing the implantable lead distally along an insertion axis, retracting the implantable lead proximally along the insertion axis, or steering the implantable lead along a lateral direction from the insertion axis). Re-positioning may be further supplemented by fluoroscopy or anatomical landmarks/markers. Methods may also include sequentially stimulating and re-positioning the lead until an optimal lead positioning near the nerve tissue is achieved. After initial lead placement is completed, the user may further adjust a stimulation amplitude threshold of the test stimulation for each electrode in proportional increments to achieve a desired stimulation-induced EMG motor response at a minimum stimulation amplitude threshold and/or provide input related to the EMG record associated with each test stimulation or a sensory response from the patient associated with the stimulation amplitude threshold for each electrode.
Systems for improved positioning of an implantable lead in a patient are also provided by the present invention. The system may comprise an integrated EMG and stimulation clinician programmer, an implantable lead coupleable to the clinician programmer, wherein the implantable lead comprises at least four electrodes, and at least one EMG sensing electrode minimally invasively positionable on a skin surface or within the patient, the EMG sensing electrode coupleable to the integrated clinician programmer. The clinician programmer is configured for (1) delivering a test stimulation at a stimulation amplitude level to a nerve tissue of the patient with a principal electrode of the implantable lead, wherein the principal electrode is selected from the at least four electrodes of the implantable lead, (2) delivering test stimulations at a same stimulation amplitude level for a same period of time sequentially to each of the four electrodes of the implantable lead, (3) and recording a stimulation-induced EMG motor response with the integrated clinician programmer for the test stimulations as sensed via the at least one EMG sensing electrode so as to facilitate positioning of the implantable lead at a target stimulation region.
Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating various embodiments, are intended for purposes of illustration only and are not intended to necessarily limit the scope of the disclosure.
The present invention relates to neurostimulation treatment systems and associated devices, as well as methods of treatment, implantation/placement and configuration of such treatment systems. In particular embodiments, the invention relates to sacral nerve stimulation treatment systems configured to treat bladder dysfunctions, including overactive bladder (“OAB”), as well as fecal dysfunctions and relieve symptoms associated therewith. For ease of description, the present invention may be described in its use for OAB, it will be appreciated however that the present invention may also be utilized for any variety of neuromodulation uses, such as bowel disorders (e.g., fecal incontinence, fecal frequency, fecal urgency, and/or fecal retention), the treatment of pain or other indications, such as movement or affective disorders, as will be appreciated by one of skill in the art.
I. Neurostimulation Indications
Neurostimulation (or neuromodulation as may be used interchangeably hereunder) treatment systems, such as any of those described herein, can be used to treat a variety of ailments and associated symptoms, such as acute pain disorders, movement disorders, affective disorders, as well as bladder related dysfunction and bowel disorders. Examples of pain disorders that may be treated by neurostimulation include failed back surgery syndrome, reflex sympathetic dystrophy or complex regional pain syndrome, causalgia, arachnoiditis, and peripheral neuropathy. Movement orders include muscle paralysis, tremor, dystonia and Parkinson's disease. Affective disorders include depressions, obsessive-compulsive disorder, cluster headache, Tourette syndrome and certain types of chronic pain. Bladder related dysfunctions include but are not limited to OAB, urge incontinence, urgency-frequency, and urinary retention. OAB can include urge incontinence and urgency-frequency alone or in combination. Urge incontinence is the involuntary loss or urine associated with a sudden, strong desire to void (urgency). Urgency-frequency is the frequent, often uncontrollable urges to urinate (urgency) that often result in voiding in very small amounts (frequency). Urinary retention is the inability to empty the bladder. Neurostimulation treatments can be configured to address a particular condition by effecting neurostimulation of targeted nerve tissues relating to the sensory and/or motor control associated with that condition or associated symptom. Bowel disorders may include any of the variety of inflammatory, motility, and incontinence conditions.
In one aspect, the methods and systems described herein are particularly suited for treatment of urinary and fecal dysfunctions. These conditions have been historically under-recognized and significantly underserved by the medical community. OAB is one of the most common urinary dysfunctions. It is a complex condition characterized by the presence of bothersome urinary symptoms, including urgency, frequency, nocturia and urge incontinence. It is estimated that about 40 million Americans suffer from OAB. Of the adult population, about 16% of all men and women live with OAB symptoms.
OAB symptoms can have a significant negative impact on the psychosocial functioning and the quality of life of patients. People with OAB often restrict activities and/or develop coping strategies. Furthermore, OAB imposes a significant financial burden on individuals, their families, and healthcare organizations. The prevalence of co-morbid conditions is also significantly higher for patients with OAB than in the general population. Co-morbidities may include falls and fractures, urinary tract infections, skin infections, vulvovaginitis, cardiovascular, and central nervous system pathologies. Chronic constipation, fecal incontinence, and overlapping chronic constipation occur more frequently in patients with OAB.
Conventional treatments of OAB generally include lifestyle modifications as a first course of action. Lifestyle modifications include eliminating bladder irritants (such as caffeine) from the diet, managing fluid intake, reducing weight, stopping smoking, and managing bowel regularity. Behavioral modifications include changing voiding habits (such as bladder training and delayed voiding), training pelvic floor muscles to improve strength and control of urethral sphincter, biofeedback and techniques for urge suppression. Medications are considered a second-line treatment for OAB. These include anti-cholinergic medications (oral, transdermal patch, and gel) and oral beta-3 adrenergic agonists. However, anti-cholinergics are frequently associated with bothersome, systemic side effects including dry mouth, constipation, urinary retention, blurred vision, somnolence, and confusion. Studies have found that more than 50% of patients stop using anti-cholinergic medications within 90 days due to a lack of benefit, adverse events, or cost.
When these approaches are unsuccessful, third-line treatment options suggested by the American Urological Association include intradetrusor (bladder smooth muscle) injections of botulinum toxin (BTX), Percutaneous Tibial Nerve Stimulation (PTNS) and Sacral Nerve Stimulation (SNM). BTX is administered via a series of intradetrusor injections under cystoscopic guidance, but repeat injections of BTX are generally required every 4 to 12 months to maintain effect and BTX may undesirably result in urinary retention. A number or randomized controlled studies have shown some efficacy of BTX injections in OAB patients, but long-term safety and effectiveness of BTX for OAB is largely unknown.
PTNS therapy consists of weekly, 30-minute sessions over a period of 12 weeks, each session using electrical stimulation that is delivered from a hand-held stimulator to the sacral plexus via the tibial nerve. For patients who respond well and continue treatment, ongoing sessions, typically every 3-4 weeks, are needed to maintain symptom reduction. There is potential for declining efficacy if patients fail to adhere to the treatment schedule. Efficacy of PTNS has been demonstrated in a few randomized-controlled studies, however, there is limited data on PTNS effectiveness beyond 3-years and PTNS is not recommended for patients seeking a cure for urge urinary incontinence (UUI) (e.g., 100% reduction in incontinence episodes) (EAU Guidelines).
II. Sacral Neuromodulation
SNM is an established therapy that provides a safe, effective, reversible, and long-lasting treatment option for the management of urge incontinence, urgency-frequency, and non-obstructive urinary retention. SNM therapy involves the use of mild electrical pulses to stimulate the sacral nerves located in the lower back. Electrodes are placed next to a sacral nerve, usually at the S3 level, by inserting the electrode leads into the corresponding foramen of the sacrum. The electrodes are inserted subcutaneously and are subsequently attached to an implantable pulse generator (IPG). The safety and effectiveness of SNM for the treatment of OAB, including durability at five years for both urge incontinence and urgency-frequency patients, is supported by multiple studies and is well-documented. SNM has also been approved to treat chronic fecal incontinence in patients who have failed or are not candidates for more conservative treatments.
A. Implantation of Sacral Neuromodulation System
Currently, SNM qualification has a trial phase, and is followed if successful by a permanent implant. The trial phase is a test stimulation period where the patient is allowed to evaluate whether the therapy is effective. Typically, there are two techniques that are utilized to perform the test stimulation. The first is an office-based procedure termed the Percutaneous Nerve Evaluation (PNE) and the other is a staged trial.
In the PNE, a foramen needle is typically used first to identify the optimal stimulation location, usually at the S3 level, and to evaluate the integrity of the sacral nerves. Motor and sensory responses are used to verify correct needle placement, as described in Table 1 below. A temporary stimulation lead (a unipolar electrode) is then placed near the sacral nerve under local anesthesia. This procedure can be performed in an office setting without fluoroscopy. The temporary lead is then connected to an external pulse generator (EPG) taped onto the skin of the patient during the trial phase. The stimulation level can be adjusted to provide an optimal comfort level for the particular patient. The patient will monitor his or her voiding for 3 to 7 days to see if there is any symptom improvement. The advantage of the PNE is that it is an incision free procedure that can be performed in the physician's office using local anesthesia. The disadvantage is that the temporary lead is not securely anchored in place and has the propensity to migrate away from the nerve with physical activity and thereby cause failure of the therapy. If a patient fails this trial test, the physician may still recommend the staged trial as described below. If the PNE trial is positive, the temporary trial lead is removed and a permanent quadri-polar tined lead is implanted along with an IPG under general anesthesia.
A staged trial involves the implantation of the permanent quadri-polar tined stimulation lead into the patient from the start. It also requires the use of a foramen needle to identify the nerve and optimal stimulation location. The lead is implanted near the S3 sacral nerve and is connected to an EPG via a lead extension. This procedure is performed under fluoroscopic guidance in an operating room and under local or general anesthesia. The EPG is adjusted to provide an optimal comfort level for the patient and the patient monitors his or her voiding for up to two weeks. If the patient obtains meaningful symptom improvement, he or she is considered a suitable candidate for permanent implantation of the IPG under general anesthesia, typically in the upper buttock area, as shown in
In regard to measuring outcomes for SNM treatment of voiding dysfunction, the voiding dysfunction indications (e.g., urge incontinence, urgency-frequency, and non-obstructive urinary retention) are evaluated by unique primary voiding diary variables. The therapy outcomes are measured using these same variables. SNM therapy is considered successful if a minimum of 50% improvement occurs in any of primary voiding diary variables compared with the baseline. For urge incontinence patients, these voiding diary variables may include: number of leaking episodes per day, number of heavy leaking episodes per day, and number of pads used per day. For patients with urgency-frequency, primary voiding diary variables may include: number of voids per day, volume voided per void and degree of urgency experienced before each void. For patients with retention, primary voiding diary variables may include: catheterized volume per catheterization and number of catheterizations per day. For fecal incontinence patients, the outcome measures captured by the voiding diary include: number of leaking episodes per week, number of leaking days per week, and degree of urgency experienced before each leak.
The mechanism of action of SNM is multifactorial and impacts the neuro-axis at several different levels. In patients with OAB, it is believed that pelvic and/or pudendal afferents can activate the inhibitory reflexes that promote bladder storage by inhibiting the afferent limb of an abnormal voiding reflex. This blocks input to the pontine micturition center, thereby restricting involuntary detrusor contractions without interfering with normal voiding patterns. For patients with urinary retention, SNM is believed to activate the pelvic and/or pudendal nerve afferents originating from the pelvic organs into the spinal cord. At the level of the spinal cord, these afferents may turn on voiding reflexes by suppressing exaggerated guarding reflexes, thus relieving symptoms of patients with urinary retention so normal voiding can be facilitated. In patients with fecal incontinence, it is hypothesized that SNM stimulates pelvic and/or pudendal afferent somatic fibers that inhibit colonic propulsive activity and activates the internal anal sphincter, which in turn improves the symptoms of fecal incontinence patients.
The present invention relates to a system adapted to deliver neurostimulation to targeted nerve tissues in a manner that results in partial or complete activation of the target nerve fibers, causes the augmentation or inhibition of neural activity in nerves, potentially the same or different than the stimulation target, that control the organs and structures associated with bladder and bowel function.
B. EMG Assisted Neurostimulation Lead Placement and Programming
While conventional sacral nerve stimulation approaches have shown efficacy in treatment of bladder and bowel related dysfunctions, there exists a need to improve positioning of the neurostimulation leads and consistency between the trial and permanent implantation positions of the lead as well as to improve methods of programming. Neurostimulation relies on consistently delivering therapeutic stimulation from a pulse generator, via one or more neurostimulation electrodes, to particular nerves or targeted regions. The neurostimulation electrodes are provided on a distal end of an implantable lead that can be advanced through a tunnel formed in patient tissue. Implantable neurostimulation systems provide patients with great freedom and mobility, but it may be easier to adjust the neurostimulation electrodes of such systems before they are surgically implanted. It is desirable for the physician to confirm that the patient has desired motor and/or sensory responses before implanting an IPG. For at least some treatments (including treatments of at least some forms of urinary and/or fecal dysfunction), demonstrating appropriate motor responses may be highly beneficial for accurate and objective lead placement while the sensory response may not be required or not available (e.g., patient is under general anesthesia).
Placement and calibration of the neurostimulation electrodes and implantable leads sufficiently close to specific nerves can be beneficial for the efficacy of treatment. Accordingly, aspects and embodiments of the present disclosure are directed to aiding and refining the accuracy and precision of neurostimulation electrode placement. Further, aspects and embodiments of the present disclosure are directed to aiding and refining protocols for setting therapeutic treatment signal parameters for a stimulation program implemented through implanted neurostimulation electrodes.
Prior to implantation of the permanent device, patients may undergo an initial testing phase to estimate potential response to treatment. As discussed above, PNE may be done under local anesthesia, using a test needle to identify the appropriate sacral nerve(s) according to a subjective sensory response by the patient. Other testing procedures can involve a two-stage surgical procedure, where a quadri-polar tined lead is implanted for a testing phase (Stage 1) to determine if patients show a sufficient reduction in symptom frequency, and if appropriate, proceeding to the permanent surgical implantation of a neuromodulation device. For testing phases and permanent implantation, determining the location of lead placement can be dependent on subjective qualitative analysis by either or both of a patient or a physician.
In exemplary embodiments, determination of whether or not an implantable lead and neurostimulation electrode is located in a desired or correct location can be accomplished through use of electromyography (“EMG”), also known as surface electromyography. EMG, is a technique that uses an EMG system or module to evaluate and record electrical activity produced by muscles, producing a record called an electromyogram. EMG detects the electrical potential generated by muscle cells when those cells are electrically or neurologically activated. The signals can be analyzed to detect activation level or recruitment order. EMG can be performed through the skin surface of a patient, intramuscularly or through electrodes disposed within a patient near target muscles, or using a combination of external and internal structures. When a muscle or nerve is stimulated by an electrode, EMG can be used to determine if the related muscle is activated, (i.e. whether the muscle fully contracts, partially contracts, or does not contract) in response to the stimulus. Accordingly, the degree of activation of a muscle can indicate whether an implantable lead or neurostimulation electrode is located in the desired or correct location on a patient. Further, the degree of activation of a muscle can indicate whether a neurostimulation electrode is providing a stimulus of sufficient strength, amplitude, frequency, or duration to affect a treatment regimen on a patient. Thus, use of EMG provides an objective and quantitative means by which to standardize placement of implantable leads and neurostimulation electrodes, reducing the subjective assessment of patient sensory responses.
In some approaches, positional titration procedures may optionally be based in part on a paresthesia or pain-based subjective response from a patient. In contrast, EMG triggers a measurable and discrete muscular reaction. As the efficacy of treatment often relies on precise placement of the neurostimulation electrodes at target tissue locations and the consistent, repeatable delivery of neurostimulation therapy, using an objective EMG measurement can substantially improve the utility and success of SNM treatment. The measurable muscular reaction can be a partial or a complete muscular contraction, including a response below the triggering of an observable motor response, such as those shown in Table 1, depending on the stimulation of the target muscle. In addition, by utilizing a trial system that allows the neurostimulation lead to remain implanted for use in the permanently implanted system, the efficacy and outcome of the permanently implanted system is more consistent with the results of the trial period, which moreover leads to improved patient outcomes.
C. Example System Embodiments
In one aspect, the CP 60 is used by a physician to adjust the settings of the EPG and/or IPG while the lead is implanted within the patient. The CP can be a tablet computer used by the clinician to program the IPG, or to control the EPG during the trial period. The CP can also include capability to record stimulation-induced electromyograms to facilitate lead placement and programming. The patient remote 70 can allow the patient to turn the stimulation on or off, or to vary stimulation from the IPG while implanted, or from the EPG during the trial phase.
In another aspect, the CP 60 has a control unit which can include a microprocessor and specialized computer-code instructions for implementing methods and systems for use by a physician in deploying the treatment system and setting up treatment parameters. The CP generally includes a graphical user interface, an EMG module, an EMG input that can couple to an EMG output stimulation cable, an EMG stimulation signal generator, and a stimulation power source. The stimulation cable can further be configured to couple to any or all of an access device (e.g., a foramen needle), a treatment lead of the system, or the like. The EMG input may be configured to be coupled with one or more sensory patch electrode(s) for attachment to the skin of the patient adjacent a muscle (e.g., a muscle enervated by a target nerve). Other connectors of the CP may be configured for coupling with an electrical ground or ground patch, an electrical pulse generator (e.g., an EPG or an IPG), or the like. As noted above, the CP can include a module with hardware and computer-code to execute EMG analysis, where the module can be a component of the control unit microprocessor, a pre-processing unit coupled to or in-line with the stimulation and/or sensory cables, or the like.
In other aspects, the CP 60 allows the clinician to read the impedance of each electrode contact whenever the lead is connected to an EPG, an IPG or a CP to ensure reliable connection is made and the lead is intact. This may be used as an initial step in both positioning the lead and in programming the leads to ensure the electrodes are properly functioning. The CP 60 is also able to save and display previous (e.g., up to the last four) programs that were used by a patient to help facilitate re-programming. In some embodiments, the CP 60 further includes a USB port for saving reports to a USB drive and a charging port. The CP is configured to operate in combination with an EPG when placing leads in a patient body as well with the IPG during programming. The CP can be electronically coupled to the EPG during test simulation through a specialized cable set or through wireless communication, thereby allowing the CP to configure, modify, or otherwise program the electrodes on the leads connected to the EPG. The CP may also include physical on/off buttons to turn the CP on and off and/or to turn stimulation on and off.
The electrical pulses generated by the EPG and IPG are delivered to one or more targeted nerves via one or more neurostimulation electrodes at or near a distal end of each of one or more leads. The leads can have a variety of shapes, can be a variety of sizes, and can be made from a variety of materials, which size, shape, and materials can be tailored to the specific treatment application. While in this embodiment, the lead is of a suitable size and length to extend from the IPG and through one of the foramen of the sacrum to a targeted sacral nerve, in various other applications, the leads may be, for example, implanted in a peripheral portion of the patient's body, such as in the arms or legs, and can be configured to deliver electrical pulses to the peripheral nerve such as may be used to relieve chronic pain. It is appreciated that the leads and/or the stimulation programs may vary according to the nerves being targeted.
Properties of the electrical pulses can be controlled via a controller of the implanted pulse generator. In some embodiments, these properties can include, for example, the frequency, amplitude, pattern, duration, or other aspects of the electrical pulses. These properties can include, for example, a voltage, a current, or the like. This control of the electrical pulses can include the creation of one or more electrical pulse programs, plans, or patterns, and in some embodiments, this can include the selection of one or more pre-existing electrical pulse programs, plans, or patterns. In the embodiment depicted in
In some embodiments, the trial neurostimulation system utilizes an EPG 80 within an EPG patch 81 that is adhered to the skin of a patient and is coupled to the implanted neurostimulation lead 20 through a lead extension 22, which is coupled with the lead 20 through a connector 21. This extension and connector structure allows the lead to be extended so that the EPG patch can be placed on the abdomen and allows use of a lead having a length suitable for permanent implantation should the trial prove successful. This approach may utilize two percutaneous incisions, the connector provided in the first incision and the lead extensions extending through the second percutaneous incision, there being a short tunneling distance (e.g., about 10 cm) there between. This technique may also minimize movement of an implanted lead during conversion of the trial system to a permanently implanted system.
In one aspect, the EPG unit is wirelessly controlled by a patient remote and/or the CP in a similar or identical manner as the IPG of a permanently implanted system. The physician or patient may alter treatment provided by the EPG through use of such portable remotes or programmers and the treatments delivered are recorded on a memory of the programmer for use in determining a treatment suitable for use in a permanently implanted system. The CP can be used in lead placement, programming and/or stimulation control in each of the trial and permanent nerve stimulation systems. In addition, each nerve stimulation system allows the patient to control stimulation or monitor battery status with the patient remote. This configuration is advantageous as it allows for an almost seamless transition between the trial system and the permanent system. From the patient's viewpoint, the systems will operate in the same manner and be controlled in the same manner, such that the patient's subjective experience in using the trial system more closely matches what would be experienced in using the permanently implanted system. Thus, this configuration reduces any uncertainties the patient may have as to how the system will operate and be controlled such that the patient will be more likely to convert a trial system to a permanent system.
As shown in the detailed view of
In one aspect, the IPG is rechargeable wirelessly through conductive coupling by use of a charging device 50 (CD), which is a portable device powered by a rechargeable battery to allow patient mobility while charging. The CD is used for transcutaneous charging of the IPG through RF induction. The CD can either be patched to the patient's skin using an adhesive or can be held in place using a belt 53 or by an adhesive patch 52, such as shown in the schematic of
The system may further include a patient remote 70 and CP 60, each configured to wirelessly communicate with the implanted IPG, or with the EPG during a trial, as shown in the schematic of the nerve stimulation system in
One or more properties of the electrical pulses can be controlled via a controller of the IPG or EPG. In some embodiments, these properties can include, for example, the frequency, amplitude, pattern, duration, or other aspects of the timing and magnitude of the electrical pulses. These properties can further include, for example, a voltage, a current, or the like. This control of the electrical pulses can include the creation of one or more electrical pulse programs, plans, or patterns, and in some embodiments, this can include the selection of one or more pre-existing electrical pulse programs, plans, or patterns. In one aspect, the IPG 100 includes a controller having one or more pulse programs, plans, or patterns that may be created and/or pre-programmed. In some embodiments, the IPG can be programmed to vary stimulation parameters including pulse amplitude in a range from 0 mA to 10 mA, pulse width in a range from 50 μs to 500 μs, pulse frequency in a range from 5 Hz to 250 Hz, stimulation modes (e.g., continuous or cycling), and electrode configuration (e.g., anode, cathode, or off), to achieve the optimal therapeutic outcome specific to the patient. In particular, this allows for an optimal setting to be determined for each patient even though each parameter may vary from person to person.
As shown in
In some embodiment, such as that shown in
In one aspect, utilization of ceramic material provides an efficient, radio-frequency-transparent window for wireless communication with the external patient remote and clinician's programmer as the communication antenna is housed inside the hermetic ceramic case. This ceramic window has further facilitated miniaturization of the implant while maintaining an efficient, radio-frequency-transparent window for long term and reliable wireless communication between the IPG and external controllers, such as the patient remote and CP. The IPG's wireless communication is generally stable over the lifetime of the device, unlike prior art products where the communication antenna is placed in the header outside the hermetic case. The communication reliability of such prior art devices tends to degrade due to the change in dielectric constant of the header material in the human body over time.
In another aspect, the ferrite core is part of the charging coil assembly 15, shown in
In one aspect, the CP 60 is used to program the IPG/EPG according to various stimulation modes, which can be determined by the CP or selected by the physician using the CP. In some embodiments, the IPG/EPG may be configured with two stimulation modes: continuous mode and cycling mode. The cycling mode saves energy in comparison to the continuous mode, thereby extending the recharge interval of the battery and lifetime of the device. The cycling mode may also help reduce the risk of neural adaptation for some patients. Neural adaptation is a change over time in the responsiveness of the neural system to a constant stimulus. Thus, cycling mode may also mitigate neural adaptation so to provide longer-term therapeutic benefit.
To activate an axon of a nerve fiber, one needs to apply an electric field outside of the axon to create a voltage gradient across its membrane. This can be achieved by pumping charge between the electrodes of a stimulator. Action potentials, which transmit information through the nervous system, are generated when the outside of the nerve is depolarized to a certain threshold, which is determined by the amount of current delivered. To generate continuous action potentials in the axon, this extracellular gradient threshold needs to be reached with the delivery of each stimulation pulse.
In conventional systems, a constant voltage power source is able to maintain the output voltage of the electrodes, so that enough current is delivered to activate the axon at initial implantation. However, during the first several weeks following implantation, tissue encapsulation around electrodes occurs, which results in an impedance (tissue resistance) increase. According to the ohms' law (I=V/R where I is the current, V the voltage and R the tissue impedance of the electrode pair), current delivered by a constant voltage stimulator will therefore decrease, generating a smaller gradient around the nerve. When the impedance reaches a certain value, extracellular depolarization will go down below the threshold value, so that no more action potential can be generated in the axon. Patients will need to adjust the voltage of their system to re-adjust the current, and restore the efficacy of the therapy.
In contrast, embodiments of the present invention utilize a constant current power source. In one aspect, the system uses feedback to adjust the voltage in such a way that the current is maintained regardless of what happens to the impedance (until one hits the compliance limit of the device), so that the gradient field around the nerve is maintained overtime. Using a constant current stimulator keeps delivering the same current that is initially selected regardless the impedance change, for a maintained therapeutic efficacy.
D. Workflows for Lead Placement, Programming and Reprogramming with CP
III. Neurostimulation Lead Placement with EMG
Placement of the neurostimulation lead requires localization of the targeted nerve and subsequent positioning of the neurostimulation lead at the target location. Various ancillary components are used for localization of the target nerve and subsequent implantation of the lead and IPG. Such components include a foramen needle and a stylet, a directional guide, dilator and an introducer sheath, straight or curved tip stylet (inserted in tined leads), tunneling tools (a bendable tunneling rod with sharp tip on one end and a handle on the other with a transparent tubing over the tunneling rod) and often an over-the-shelf torque wrench. The foramen needle and stylet are used for locating the correct sacral foramen for implant lead and subsequent acute stimulation testing. The physician locates the targeted nerve by inserting a foramen needle and energizing a portion of needle until a neuromuscular response is observed that is indicative of neurostimulation in the target area (see Table 1 above). After the target nerve is successfully located, the direction guide, introducer and dilator are used to prepare a path along which the lead can be implanted. The directional guide is a metal rod that holds the position in the sacral foramen determined with the foramen needle for subsequent placement of the introducer sheath and dilator. The introducer sheath and dilator is a tool that increases the diameter of the hole through the foramen to allow introduction of the permanent lead. The lead stylet is a stiff wire that is inserted into the lead to increase its stiffness during lead placement and may be configured with a straight or curved tip. The torque wrench is a small wrench used to tighten the set screw that locks the lead into the IPG. The tunneling tool is a stiff, sharp device that creates a subcutaneous tunnel, allowing the lead to be placed along a path under the skin. While such approaches have sufficed for many conventional treatments, such approaches often lack resolution and may result in sub-optimal lead placement, which may unnecessarily complicate subsequent programming and result in unfavorable patient outcomes. Thus, an approach that provides more accurate and robust neural localization while improving ease of use by the physician and the patient.
A. EMG Assisted System Setup for Neural Localization and Lead Placement
In one aspect, the system utilizes EMG to improve the accuracy and resolution of neural localization with the foramen needle as well as to improve consistency and ease of performing each of neural localization and lead placement, as well as subsequent programming of the implanted neurostimulation system. In certain aspects of the invention, the system setups aim to use standard EMG recording techniques to create a unique approach to implanting a lead near the third sacral nerve and subsequent programming of electrical stimulation of the nerve. Such an approach is made feasible by integration of EMG recording, display and analysis with the CP, which is operatively coupled with the neurostimulation lead and used during lead placement and subsequent programming. Another advantageous aspect of this approach is that the use of proportional increases in stimulation amplitude during test stimulation and programming reduces the time required for these activities, as well as improve the ease with which the procedures can be conducted. In addition, recording of motor and sensory responses and stimulation amplitude thresholds directly into the CP during lead placement and conversion of these responses into feedback on the quality of lead placement and programming recommendations. Another advantageous aspect of this EMG assisted approach is that measurement and analysis of only one neuromuscular response, preferably the “big toe response,” can be used as an indicator of appropriate stimulation amplitude for effective treatment during programming of the neurostimulation system. In another aspect, automation of these aspects within the CP can further reduce the duration and complexity of the procedure and improve consistency of outcomes. For example, automation of electrode threshold determinations based on EMG responses can provide rapid feedback during lead placement and to identify optimal programming parameters.
In one aspect, the EMG signal is used to evaluate placement quality and programming quality based on stimulation amplitude to evoke a response. The EMG responses are measured based on one of several approaches for quantifying the compound muscle action potential (CMAP). Referring to the EMG waveform shown in
B. Neural Localization with Foramen Needle
In conventional approaches, the foramen needle is positioned in an area adjacent the targeted nerve and energized until the desired muscle response is observed that is indicative of the targeted nerve being stimulated. A lead with multiple electrodes is inserted at approximately the same location as the foramen needle under the assumption that one or more of the electrodes will be in a position suitable for stimulating the targeted nerve. One of the drawbacks associated with this approach is that the position of the lead may differ slightly from the position of the foramen needle. In addition, since the foramen needle identifies a particular point location of the targeted nerve and the neurostimulation electrodes are disposed along a length of the lead, often the lead may be misaligned. For example, after successfully locating the target nerve with a foramen needle and inserting the neurostimulation lead, the lead may intersect the point located with the foramen needle but extend transverse or askew of the target nerve such that neurostimulation electrodes more distal and proximal of the intersecting point do not provide effective neurostimulation of the target nerve when energized, thereby limiting the neurostimulation programs available, which may lead to sub-optimal patient outcomes. Thus, while the foramen needle is effective in locating the target nerve at a particular point, often it does not provide enough resolution to ensure that the neurostimulation lead is properly positioned and aligned with the target nerve along the entire length on which the neurostimulation electrodes are disposed.
In accordance with aspects of the present invention, the recorded EMG is used to facilitate neural localization with a foramen needle. Typically, a foramen needle includes a discrete electrode that is stimulated until a desired neuromuscular response is observed. In one aspect, the stimulation level is increased until a desired EMG response (e.g. anal bellows and/or big toe) is recorded, at which point the associated amplitude is recorded as well, typically at a constant current. The user may increase the stimulation level in desired increments or the system may automatically increase the stimulation until the EMG response is recorded.
As shown in
In some embodiments, the display provides feedback to the user (e.g. color coding) as to whether the foramen needle is at the targeted nerve based on the EMG and amplitude measurements. For example, the tip of the foramen representation may be green to indicate a “good” position: (<2 mA); yellow may indicate an “ok” position (2-4 mA) and red may indicate a “bad” position (>4 mA). In some embodiments, the system is configured such that amplitude adjustment is performed in auto-adjusting increments. In one example, from 0-1 mA, step-size is 0.05 mA; from 1-2 mA, step-size is 0.1 mA; from 2 mA-3 mA, step-size is 0.2 mA; and from 2 mA+, step-size is 0.25 mA. In some embodiments, the system may include an option to turn off auto-adjusting increments and use fixed increments, such as fixed increments of 0.05 or 0.1 mA.
C. Lead Placement with EMG
After neural localization is complete, the neurostimulation lead is advanced to the target location identified during neural localization. Typically, a neurostimulation lead include multiple electrodes along a distal portion of the lead, as can be seen in
In one aspect, the system provides improved lead placement by determining lead position of a multi-electrode lead relative the target nerve with EMG using an electrode sweeping process. This approach allows for fine tuning of lead placement. This feature utilizes a four-channel connecting cable so as to allow the system to energize each electrode in rapid succession without requiring separate attachment and detachment on each electrode with a J-clip or alligator slip, such as is used in convention methods. This aspect is advantageous since utilization of a J-clip or alligator clip to make contacts to tightly pitched electrode is difficult and time consuming and could potentially result in movement of the lead during testing.
In the sweeping process, the system identifies a principal electrode. This may be a default selection by the system or selected by the physician using the CP. The stimulation of the principal electrode is adjusted until an adequate motor response with a maximum amplitude CMAP is obtained at which point the stimulation level or amplitude is recorded. The system then sweeps through all the remaining electrodes of the lead with the same stimulation level and records the EMG responses from each electrode. Typically, the sweeping process is performed rapidly. For example each contact can be stimulated individually at the same stimulation level for 1 second such that the entire sweeping cycle can be conducted in about 4-5 seconds for a four-electrode lead. The system can determine responses for each electrode that can be used to indicate the relative distances of each electrode from the target nerve, which may also be recorded for subsequent use in programming of the EPG or IPG. There are several options as to how this sweeping process can be used to facilitate fine tuning of lead placement, including the following two options.
Option 1: In one approach, the EMG response value for each electrode can be indicated on a graphical user interface display of the clinician programmer. For example, the response value can be indicated by color coding the electrodes on the display (see
Option 2: In another approach, the response value is illustrated in terms of the distance to the target nerve determined based onx the relative response value of each electrode. In one aspect, the R-values may be converted to relative distance which allows for ready interpretation of a relative position of the electrode to the target nerve. Examples of these R-value and distance curves in regard to differing positions of the leads are described in
The axial position of the lead relative the target nerve can be reflected using the R-values for each electrode obtained during sweeping. If the lead is too shallow, the R-value curves obtained may resemble
If the lead is too shallow, the R-value curves obtained may resemble
In another aspect, the lateral displacement of the lead relative the target nerve due to tilting or angling can be reflected using the R-values obtained during the sweeping process. For example,
In some embodiments, the R-value and/or distance curves may be determined by the system and used to communicate a suggestion to the clinician, such as with the CP, as to whether the lead should be advanced, retracted or steered. In other embodiments, the R-values and/or the associated curves may be displayed on a graphical user interface of the CP so as to provide a visual indicator of the robustness of each electrode and/or its relative location. In one aspect, a suitable lead position is one in which at least three of the four electrodes are disposed adjacent to and along the targeted nerve. Due to the unique shapes of nerve structures, an optimal lead position in which all electrodes are adjacent the target nerve may not always be readily achievable.
After selection of a principal electrode, the CP performs a test stimulation on the 4-channel lead, which is typically a quick check across all electrodes of the lead (e.g., sweep). In one aspect, the CP records the EMG waveform displays 62 and 63 and the amplitude threshold reading for each selected electrode during this test stimulation. From this test stimulation, the CP 60 may display the suitability of each electrode for neurostimulation in the electrode status display 64 by a color coding or other suitable indicator. For example, in the electrode status display 64 in
D. Electrode Threshold Determination/Validation of Lead Placement
As shown in
In one aspect, the CP 60 connects to the EPG/IPG and establishes communication, which may be indicated on the graphical user interface as shown in
In order to confirm correct lead placement, it is desirable for the physician to confirm that the patient has both adequate motor and sensory responses before transitioning the patient into the staged trial phase or implanting the permanent IPG. However, sensory response is a subjective evaluation and may not always be available, such as when the patient is under general anesthesia. Experiments have shown that demonstrating appropriate motor responses is advantageous for accurate placement, even if sensory responses are available. As discussed above, EMG is a tool which records electrical activity of skeletal muscles. This sensing feature provides an objective criterion for the clinician to determine if the sacral nerve stimulation results in adequate motor response rather than relying solely on subjective sensory criteria. EMG can be used not only to verify optimal lead position during lead placement, but also to provide a standardized and more accurate approach to determine electrode thresholds, which in turn provides quantitative information supporting electrode selection for subsequent determinations of electrode recommendation and programming, discussed in further detail below. Using EMG to verify activation of motor responses can further improve the lead placement performance of less experienced operators and allow such physicians to perform lead placement with confidence and greater accuracy. Advantageously, as the positioning and programming functionality are integrated in many embodiments of the clinician programmer, at least some of the validation thresholds may be correlated to the subsequent stimulation programming, so that (for example) positioning is validated for a particular programming protocol to be used with that patient. Regardless, stimulation programming protocols may employ EMG data obtained during lead positioning or validation to more efficiently derive suitable neurostimulation treatment parameters for that patient.
While the above illustrates an example method of integrating the CP 60 with EMG measurements to assist in placement of the lead it is appreciated that various other aspects and features may be used in accordance with aspects of the invention. The following Table 2 illustrates various features of EMG enhanced lead placement used in a various devices as well as various other alternative features.
IV. Neurostimulation Programming with EMG
After implantation of the lead and placement of the neurostimulation is verified with the CP using EMG, the CP can be used outside the operating room to program the IPG/EPG for delivery of the neurostimulation treatment. Programming may be performed using thresholds obtained from EMG obtained during and/or after lead placement and tested using EMG data associated with at least one neuromuscular response.
A. EMG Assisted Programming Setup
In one aspect, the integration of the EMG recording and display into the clinician tool used for lead placement and programming provides significant advantages over conventional programming methods, including a reduction in time required to determine a program that is efficacious in providing relief for the treated condition. In addition, the use of proportional increases in stimulation amplitude during test programming to reduce the time required for these activities. Recording of motor and sensory responses and stimulation amplitude thresholds directly into the CP during lead placement and conversion of these responses into feedback on the quality of programming recommendations. In another aspect, methods may utilize an EMG recording of a single neuromuscular response (e.g. big toe) to verify the appropriate electrode position and selection and then tune down the amplitude so as to avoid invoking the neuromuscular response during long term therapy stimulation. This aspect may simplify and reduce the time associated with programming of the neurostimulation device as well as improve patient comfort during programming and long term therapy. In another aspect, the CP is configured with an automated threshold determination based on EMG responses to provide rapid feedback during lead placement and to identify optimal programming parameters.
In some embodiments, the system is configured to have EMG sensing capability during re-programming, which is particularly valuable. Stimulation levels during re-programming are typically low to avoid patient discomfort which often results in difficult generation of motor responses. Involuntary muscle movement while the patient is awake may also cause noise that is difficult for the physician to differentiate. In contrast to conventional approaches, EMG allows the clinician to detect motor responses at very low stimulation levels at which the responses are not visible to the naked eye, and help them distinguish a motor response originated by sacral nerve stimulation from involuntary muscle movement.
In some embodiments, the system stores the last four programs used onboard a memory of the IPG/EPG. This is particularly advantageous for reprogramming as it allows a physician to access the most recent programs used in the neurostimulation with an entirely different CP that may not otherwise have access to the programming information. In another aspect, the programming data may be accessible online or on a cloud serve and associated with an unique identifier of a given IPG/EPG such that a different CP could readily access and download programming information as needed for re-programming.
B. Electrode Characterization
In one aspect, during lead placement, the CP 60 can utilize the thresholds previously recorded in characterizing each electrode as to its suitability for use in neurostimulation. In some embodiments, the CP 60 is configured to program the IPG/EPG with an EMG recording from only one muscle, either the anal bellows or the big toe response. Such programming can also utilize a visual observation of the response as well as the recorded maximum response amplitude. In one aspect, the CP 60 performs programming without requiring an anal bellow response observation or EMG waveform measurement of an anal bellows response. In some embodiments, the CP 60 performs programming using an EMG recording from only the big toe response, such as shown in
In one aspect, the EMG recording may be that obtained during lead placement, or more typically, obtained during programming so that the patient can provide subjective sensory response data concurrent with performing a big toe response with a given electrode during testing. The programming may further include visual observations of the big toe response and/or the maximum response amplitude obtained during programming. Allowing programming of the IPG/EPG without requiring an anal bellow response is advantageous since the patient is not under general anesthesia while programming is performed and the anal bellows response can be uncomfortable and painful for the patient. This also allows the CP to receive subjective sensory data from the patient during programming as to any discomfort, paresthesia or pain associated with stimulation of a particular electrode configuration. The following Table 3 shows various features of EMG-enabled neurostimulation programming of the IPG/EPG with the CP as used in various devices as well as alternative features.
In one aspect, the electrodes can be configured to deliver neurostimulation in varying electrode configurations, for example, neurostimulation may be delivered in a mono-polar mode from one or more of the electrodes in various combinations and sequences and/or in a bi-polar mode between two or more electrodes in various combinations and sequences. The suitability of the programming can be determined by use of the electrode characterizations described above determined from EMG recording of at least one neuromuscular response, typically the big toe response, and may further include visual response and amplitude data and subject sensory response data from the patient. From these characterizations, the CP determines multiple electrode configuration recommendations, which may be provided on the graphical user interface of the CP 60 on the Electrode Recommendation display 67 to allow the physician to review and select each recommendation for subsequent testing.
C. Electrode Configuration Recommendations
In one aspect, the system configuration determines multiple electrode configuration recommendations based on using electrode characterization and/or threshold data based in part on EMG recordings of the electrodes and provides the recommendations to the user.
In one aspect, the electrode configurations are determined based on the threshold data according to the following rules: (1) Assign single cathode configurations for each contact in the “Good” tier, prioritized from farthest pair to closest pair; (2) Assign single cathode configurations for each contact in the “Good” tier, prioritized from lowest to highest threshold; (3) Assign double cathode configurations for each pair of adjacent electrodes in “Good” tier, prioritized by lowest combined threshold; (4) Assign single cathode configurations for each contact in the “OK” tier, prioritized from lowest to highest threshold; and (5) Assign double cathode configurations for each pair of adjacent electrodes from “Good” and “OK” tiers, prioritized by lowest combined threshold. The anodes for the cathode configurations are assigned as follows: for monopolar configuration, the IPG housing or “can” is assigned as the anode; for bipolar configuration, the electrode furthest from the cathode with acceptable impedance is assigned as the anode.
After identification of the electrode configuration recommendations, the system presents the electrode configuration recommendations to the physician, typically on a user interface of the CP such as shown in
In one aspect, in an idealized setting in which each of the electrodes has a “good” impedance, the system simply recommends each of the contacts as a single cathode. Although it is desirable to have four “good” electrodes, it is acceptable to have at least three “good” electrodes for initial programming. The above algorithm recommends the best electrode selection for a given case. While each physician may have their own way to select electrode for programming, providing a set of electrode configuration recommendations that are easily viewed and selected by the physician helps standardize the process, reduce the duration of the procedure and provide improve patient outcomes, particularly for inexperienced implanters or minimally trained personnel.
In one aspect, the above algorithm assumes a single input parameter for the electrode threshold. In some embodiments, the system allows the physician to select, through the CP, what parameter(s) (sensory or motor responses or in combination) to use to determine the threshold for each electrode. The physician can also select whether to rely on EMG feedback or not for threshold determination. In another aspect, qualitative sensory feedback will be considered in electrode selection, e.g., if a patient reports unpleasant sensation for any specific electrode, this electrode will be excluded from being used as cathode. In another aspect, the algorithm prioritizes single cathode over double cathodes for all contacts in the “good” tier. In some embodiments, the electrodes are tiered according to the following tiers: “good”=“1-3 mA”; “ok”=“0.5-1 mA” and “3-4 mA”; “bad”=“<0.5 mA” and “>4 mA.”
D. Program Selection, Modification and Testing
In programming the neurostimulation system, an EMG signal can be used to evaluate programming quality by allowing user to see if a motor response is evoked by stimulation. In some embodiments, the user can manually observe EMG responses and enter the observations into the CP and try to set a stimulation amplitude at a level that evokes a desired motor response.
In the first electrode configuration recommendation in
In one aspect, the graphical user interface allows the user to adjust various parameters associated with each of the recommended electrode configurations being tested. For example, as shown in
In one aspect, after programming of the IPG/EPG in accordance with the above described methods, the patient evaluates the selected program over a pre-determined period of time. Typically, the patient is able to make limited adjustments to the program, such as increasing or decreasing the amplitude or turning the treatment off. If after the assessment period, the patient has not experienced relief from the treated condition or if other problems develop, the patient returns to the physician and a re-programming of the IPG/EPG is conducted with the CP in a process similar to the programming methods described above, to select an alternative electrode configuration from the recommended configuration or to develop a new treatment program that provides effective treatment.
In the foregoing specification, the invention is described with reference to specific embodiments thereof, but those skilled in the art will recognize that the invention is not limited thereto. Various features and aspects of the above-described invention can be used individually or jointly. Further, the invention can be utilized in any number of environments and applications beyond those described herein without departing from the broader spirit and scope of the specification. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be recognized that the terms “comprising,” “including,” and “having,” as used herein, are specifically intended to be read as open-ended terms of art.
The present application is a continuation of U.S. application Ser. No. 14/827,108 entitled “ELECTROMYOGRAPHIC LEAD POSITIONING AND STIMULATION TITRATION IN A NERVE STIMULATION SYSTEM FOR TREATMENT OF OVERACTIVE BLADDER,” filed on Aug. 14, 2015, which claims the benefit of priority of U.S. Provisional Application Nos. 62/038,131 filed on Aug. 15, 2014; 62/041,611 filed on Aug. 25, 2014; and 62/101,888 filed on Jan. 9, 2015; the entire contents of which are incorporated herein by reference in their entireties for all purposes. The present application is related to pending U.S. Non-Provisional patent application Ser. No. 14/827,074, U.S. Application Publication 2016/0045724, entitled “Devices and Methods for Anchoring of Neurostimulation Leads”; pending U.S. Non-Provisional patent application Ser. No. 14/827,081, U.S. Application Publication 2016/0045745, entitled “External Pulse Generator Device and Associated Methods for Trial Nerve Stimulation”; pending U.S. Non-Provisional patent application Ser. Nos. 14/827,095, U.S. Application Publication 2016/0045746, entitled “Integrated Electromyographic Clinician Programmer For Use With an Implantable Neurostimulator” and pending U.S. Non-Provisional patent application Ser. Nos. 14/827,067, U.S. Application Publication 2016/0045751, entitled “Systems and Methods for Neurostimulation Electrode Configurations Based on Neural Localization”; and U.S. Provisional Application Nos. 62/101,666, entitled “Patient Remote and Associated Methods of Use With a Nerve Stimulation System” filed on Jan. 9, 2015; 62/101,884, entitled “Attachment Devices and Associated Methods of Use With a Nerve Stimulation Charging Device” filed on Jan. 9, 2015; 62/101,782, entitled “Improved Antenna and Methods of Use For an Implantable Nerve Stimulator” filed on Jan. 9, 2015; and 62/191,134, entitled “Implantable Nerve Stimulator Having Internal Electronics Without ASIC and Methods of Use” filed on Jul. 10, 2015; each of which is assigned to the same assignee and incorporated herein by reference in its entirety for all purposes.
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| Child | 14991752 | US |
