Patent Application
20230248962
The invention relates to a wearable electronic medical device for transcutaneous electrical stimulation of peripheral nerves for the purpose of treating one or more conditions.
There are many known technologies that use electrical stimulation of peripheral nerves to treat conditions. Implantable stimulation technologies require surgical implantation of stimulation leads, with a pulse generator that is either surgically implanted or connected externally to wire leads. Percutaneous stimulation technologies are less invasive, but still require the stimulation electrodes to pierce the skin. While these technologies can be effective in treating certain conditions, they are less desirable due to their invasiveness and because they can require the continued or routine attention of specialists, requiring doctor's office visits, phone calls, etc.
A system for applying transcutaneous electrical stimulation can includes a wearable, such as a garment, sock, sleeve, brace, strap, etc. The wearable includes an electronic stimulator device that provides transcutaneous electrical stimulation to peripheral nerves for treatment of medical conditions. Advantageously, the wearable allows the subject to use the system at a time and place that is convenient. The subject may choose to use the device while they are at work or at home, or while walking, relaxing, or sleeping, as long as certain environments and/or activities (e.g., wet environments/activities) are avoided. Since there are no implantable or percutaneous components, the risk of infection, battery fault burns, and transcutaneous power transfer discomfort and/or bleeding, are greatly reduced or eliminated.
The wearable includes electrodes that are arranged in a predetermined pattern or array, and that engage the subject's skin at desired locations when the wearable is worn. These skin surface mounted electrodes can, for example, be similar to those of other transcutaneous electrical nerve stimulation (“TENS”) units to implement high voltage skin surface electrical stimulation. The electrodes include stimulating electrodes and recording electrodes, which the wearable can position at the same location or at different locations on the subject's skin. In fact, the identities of individual electrodes, i.e., stimulating or recording, can change depending on the application/treatment for which the system is being used. The stimulating electrodes apply the transcutaneous electrical stimulation to the subject's skin, and the recording electrodes record the electromyogram (EMG) responses elicited by the stimulation.
The wearable also includes a control unit that is electrically connected to the electrodes and that is operable to control electrical stimulation applied by the stimulating electrodes and to control the recording of EMG responses by the recording electrodes. The control unit can execute closed-loop control algorithms, which adjust stimulation patterns, periodically or constantly, based on the elicited EMG response from the recruited nerves as feedback. The control unit can execute open-loop control algorithms, which can administer stimulation patterns, periodically or constantly, with or without adjustment, and without feedback. The control unit can execute hybrid control algorithms, which execute both closed-loop and open-loop control algorithms based on stimulation and/or recording sensor indications.
Alternatively, instead of the EMG response providing the closed-loop feedback, or as a supplement to the EMG response, the system can include alternative devices, such as mechanomyogram (MMG) devices (e.g., an accelerometer), or can implement electronic measurements, such as electrode impedance, to implement the closed-loop control.
This closed-loop control can eliminate the need for “programming sessions” commonly required for neurostimulation systems. The day-to-day variability that arises due to electrode placement and skin impedance necessitates these sessions to make sure that the electrodes are positioned to provide adequate stimulation treatment. With the present system, instead of physically adjusting the electrode positions on the subject in order to find the arrangement that produces the desired response, the system itself can select which electrodes to use, and can adjust the number and pattern of electrodes until an acceptable response (EMG and/or MMG) is achieved. Once the appropriate electrodes pattern is identified, the order, intensity, timing, etc. of the stimulation can be further tuned or adjusted to optimize the EMG and/or MMG response. The system can tailor the electrical stimulation applied by each individually controllable electrode in the array so that the stimulation characteristics of each electrode (e.g., frequency, amplitude, pattern, duration, etc.) is configured to deliver the desired stimulation effect. This tailoring can be implemented automatically through the algorithm, which incrementally adjusts these characteristics, monitoring the and/or response at each increment until optimal settings are identified. Stimulation therapy can then be applied with these settings, according to the algorithm, which can be dictated by the requirements of the treating physician.
Throughout the electrical stimulation treatment process, the system can implement periodic or continuous measurement of system integrity. One such measurement is that of electrode impedance to remove the risks that can arise when electrodes lift away from the skin or certain properties of the electrodes deteriorate. The impedance measurement capability could also potentially be used to provide an indication of the optimal electrode location for nerve stimulation. This may be the case, for example, in areas where the skin is thin and where the stimulated nerves are most superficial. Thus, impedance values may be used as an input to the closed-loop stimulation algorithm to adjust stimulation patterns. By way of example, when stimulating the tibial nerve, the posterior area of the medial malleolus typically has comparatively thin skin and is the site where tibial nerve is most superficial, which leads to its being a good candidate for measuring electrode impedance.
The control unit and the architecture of the system may be designed to constantly optimize stimulation by monitoring the quality of nerve recruitment periodically or on a pulse-by-pulse basis, with the goal of keeping recruitment strength to a minimum (which can reduce muscle twitching) and to minimize the stimulation energy being delivered through the skin. The EMG recording feature is capable of detecting both M-wave and F-wave responses, which can be used as feedback inputs (together or independently) to the closed-loop stimulation algorithm to determine the level of activation of the stimulated peripheral nerve. A significant aspect of the F-wave is that it provides an indication that the stimulation-evoked peripheral nerve action potential has activated motor neurons in the associated spinal cord nerves/nerve plexus. For example, an F-wave response to tibial nerve stimulation indicates that the tibial nerve action potential has activated motor neurons in the sacral spinal cord/sacral plexus.
The wearable transcutaneous electrical stimulation device can be used to stimulate various peripheral nerves in order to treat medical conditions associated with those nerves. For example, the system can be used to apply electrical stimulation to the tibial nerve to treat pelvic floor dysfunction, e.g., overactive bladder (OAB) medical conditions. As another example, the system can be used to apply electrical stimulation to the tibial nerve to treat sexual dysfunction. In this manner, it is believed that tibial nerve stimulation could be used to treat genital arousal aspects of female sexual interest/arousal disorder by improving pelvic blood flow. In yet another example, the system can be used to apply electrical stimulation to the tibial nerve to treat plantar fasciitis.
As another example, the system can be applied to the wrist area to provide stimulation to the ulnar nerve and/or median nerve. The stimulation electrode array can, for example, be placed on the inside of the lower arm anywhere 0 to 20 cm from the wrist line. EMG recording electrodes can be placed on the base of thumb to record signal from abductor/flexor pollicis brevis. EMG recording electrodes alternatively or additionally can be placed on the base of pinky to record signal from abductor/flexor digiti minimi brevis. The nerve activation could be confirmed by recording M-wave and F-wave EMG signals from the relevant muscles. The EMG signal can also be used as a control signal to adjust the stimulation parameters or stimulation electrode patterns. This technology can be applied to median nerve activation for pain management in carpal tunnel syndrome, hypertension management, and nerve conduction study/nerve injury diagnosis for median/ulnar nerve neuropathy, etc.
As a further example, the system can be used to apply transcutaneous electrical stimulation to provide neurostimulation to peripheral nerves in order to enhance nerve regeneration after peripheral nerve injury.
Implementing closed-loop control, the system can utilize measured EMG responses to detect and obtain data related to the electrical activity of muscles in response to the applied stimulation. This data can be used as feedback to tailor the application of the electrical stimulation. Additionally or alternatively, the system can also implement MMG sensors, such as accelerometers, to measure the physical response of the muscles. Other feedback, such as impedance measurements between electrodes and other biopotential recording, can also be utilized. Through this closed-loop implementation, the system can utilize techniques such as current steering and nerve localization to provide peripheral nerve stimulation therapy for treating various medical conditions.
The system, method, and apparatus for applying transcutaneous electrical stimulation disclosed herein has many aspects, which can be included or utilized in various combinations.
According to one aspect, a system, method, and apparatus treats a condition by applying transcutaneous electrical stimulation to a target peripheral nerve of a subject.
According to another aspect, alone or in combination with any other aspect, the system, method, and apparatus can include positioning a plurality of stimulation electrodes on a skin surface proximate the targeted peripheral nerve. The method also can include positioning one or more recording electrodes on a skin surface remote from the stimulation electrodes at a location where electromyogram (EMG) responses to electrical stimulation of the targeted peripheral nerve can be detected. The method also can include stimulating the peripheral nerve by applying electrical stimulation pulses via the stimulation electrodes according to stimulation parameters under closed-loop control in which EMG responses to the electrical stimulation pulses are monitored via the recording electrodes and the stimulation parameters are adjusted in response to the monitored EMG responses.
According to another aspect, alone or in combination with any other aspect, the system, method, and apparatus can include, in response to detecting an unacceptable condition of the recording electrodes, applying electrical stimulation pulses via the stimulation electrode pattern according to the stimulation parameters under open-loop control in which the stimulation parameters are maintained without adjustment.
According to another aspect, alone or in combination with any other aspect, the system, method, and apparatus can include a plurality of electrical stimulation electrodes spaced from each other in a predetermined configuration, one or more recording electrodes, a structure for supporting the stimulation electrodes and the recording electrodes spaced apart from each other, and a control unit for controlling the operation of the stimulation electrodes and the recording electrodes. The control unit is configured to energize the stimulation electrodes under closed-loop control using the recording electrodes to measure feedback, energize the stimulation electrodes under open-loop without measuring feedback, and determine whether to energize the stimulation electrodes under closed-loop control or open-loop control based on determining whether the feedback measured by the recording electrodes is reliable.
According to another aspect, alone or in combination with any other aspect, the structure for supporting the stimulation electrodes and the recording electrodes can include a wearable structure configured to position the stimulation electrodes in the proximity of a peripheral nerve and to position the recording electrodes in the proximity of a muscle activated by the peripheral nerve.
According to another aspect, alone or in combination with any other aspect, the wearable structure can position the stimulation electrodes proximate the peripheral nerve and the recording electrodes proximate a location where EMG signals that result from recruitment of the peripheral nerve's motor fibers can be detected.
According to another aspect, alone or in combination with any other aspect, the wearable structure can include a strap, wherein the stimulation electrodes and recording electrodes are positioned at different locations along the length of the strap. The strap can be configured to have a portion wrapped around the subject's ankle to position the stimulating electrodes proximate the tibial nerve between the medial malleolus and the Achilles tendon. The strap can also be configured to have a portion wrapped around the subject's foot to position the recording electrodes on the bottom of the subject's foot near the abductor hallucis and the flexor hallucis brevis.
According to another aspect, alone or in combination with any other aspect, the wearable structure can include a brace comprising an upper portion upon which the stimulation electrodes are positioned and a lower portion upon which the recording electrodes are positioned. The upper portion of the brace can be configured to be wrapped around the subject's ankle to position the stimulating electrodes proximate the tibial nerve between the medial malleolus and the Achilles tendon. The lower portion of the brace can be configured to be wrapped around the subject's foot to position the recording electrodes on the bottom of the subject's foot near the abductor hallucis and the flexor hallucis brevis.
According to another aspect, alone or in combination with any other aspect, the phase relationship or time delay can be indicative of the foot, right or left, upon which the apparatus is worn.
According to another aspect, alone or in combination with any other aspect, the wearable garment can include an ankle brace and the stimulating electrodes can include left-side stimulating electrodes and right-side stimulating electrodes configured so that the left-side electrodes are positioned adjacent the tibial nerve near the medial malleolus when worn on the right foot, and so that the right-side electrodes are positioned adjacent the tibial nerve near the medial malleolus when worn on the left foot.
According to another aspect, alone or in combination with any other aspect, the control unit can be configured to select whether to use the left-side electrodes or right-side electrodes in response to determining the foot upon which the apparatus is worn.
According to another aspect, alone or in combination with any other aspect, the apparatus can include a plurality of stimulation electrodes, and the control unit can be configured to select which of the stimulation electrodes to utilize. The control unit can also be configured to select stimulation electrode pairs and measure the impedance between the selected pairs. The control unit can be further configured to determine the foot upon which the apparatus is worn in response to the measured impedance.
According to another aspect, an apparatus for applying electrical stimulation to a target peripheral nerve in a subject includes a wearable structure configured to be worn on at least one of the subject's lower leg, foot, or ankle. A first stimulation electrode is mounted on the wearable structure at a first location on the wearable structure. A second stimulation electrode is mounted on the wearable structure at a second location on the wearable structure, different than the first location on the wearable structure. One or more recording electrodes are mounted on the wearable structure. The apparatus also includes a control unit for controlling the operation of the first stimulation electrode, the second stimulation electrode, and the one or more recording electrodes. The wearable is configured to position the first stimulation electrode on a medial side of the target peripheral nerve, and to position the second stimulation electrode on a lateral side of the target peripheral nerve. The control unit is also configured to use the first and second stimulation electrodes to apply electrical stimulation to the target peripheral nerve and to record physiological responses to the applied electrical stimulation using the recording electrodes.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to apply the electrical stimulation to the target peripheral nerve using one of the first and second stimulation electrodes as a cathode and the other of the first and second stimulation electrodes as an anode.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to apply cathodic electrical stimulation to the target peripheral nerve.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to apply anodic electrical stimulation to the target peripheral nerve.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to switch between applying cathodic and anodic electrical stimulation to the target peripheral nerve.
According to another aspect, alone or in combination with any other aspect, the target peripheral nerve can be the tibial nerve. The wearable can be configured to position the first stimulation electrode medially of the tibial nerve, and to position the second stimulation electrode laterally of the tibial nerve.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to apply electrical stimulation laterally across the tibial nerve in a direction that acts perpendicular to the axon fibers in the tibial nerve.
According to another aspect, alone or in combination with any other aspect, the wearable can be configured to position the first stimulation electrode on a skin surface of the subject located on a medial side of a cavity between an Achilles tendon, tibia bone, and fibula bone of the subject through which the tibial nerve extends, and to position the second stimulation electrode on a skin surface of the subject located on a lateral side of the cavity.
According to another aspect, alone or in combination with any other aspect, the controller can be configured to apply electrical stimulation laterally across the cavity from the medial side to the lateral side and vice versa.
According to another aspect, alone or in combination with any other aspect, the apparatus can also include electrical traces secured to the wearable structure. The electrical traces can be configured to electrically connect the stimulation electrodes and recording electrodes to the control unit.
According to another aspect, alone or in combination with any other aspect, the control unit can be configured to detect via the recording electrodes the presence of an EMG response to stimulation therapy. The control unit can be configured to, in response to detecting no EMG response, deliver stimulation therapy under open-loop control without EMG feedback. The control unit can also be configured to, in response to detecting an EMG response, deliver stimulation therapy under closed-loop control with EMG feedback.
According to another aspect, alone or in combination with any other aspect, the control unit can be configured to detect via the stimulating electrodes whether the apparatus is being worn on a right foot or left foot of the user. In response to detecting the foot, the control unit can also be configured to determine which stimulation electrode is configured as a cathode and which stimulation electrode is configured as an anode.
According to another aspect, alone or in combination with any other aspect, the wearable can include an ankle brace having a first portion configured to be strapped around a foot and to position the one or more recording electrodes on the foot. The ankle brace can also include a second portion configured to be strapped around an ankle to position the first stimulation electrode on a medial side of the target peripheral nerve, and to position the second stimulation electrode on a lateral side of the target peripheral nerve.
According to another aspect, alone or in combination with any other aspect, the wearable can include a strap having a first portion configured to be wrapped around a foot and to position the one or more recording electrodes on the foot. The strap can also include a second portion configured to be strapped around an ankle to position the first stimulation electrode on a medial side of the target peripheral nerve, and to position the second stimulation electrode on a lateral side of the target peripheral nerve.
An electronic medical device, a system including the medical device, and a method for using the medical device, is configured to apply transcutaneous electrical stimulation to peripheral nerves to treat various medical conditions.
For example, the system can be used to stimulate the tibial nerve (transcutaneous tibial nerve stimulation “TTNS”) to treat medical conditions associated with pelvic floor dysfunction, e.g., over-active bladder (OAB). In a TTNS implementation, the electronic medical device applies electrical stimulation near the medial malleolus, which activates both sensory and motor fibers in the nerve. The activation of the sensory fibers of the tibial nerve helps to treat the urge-related symptoms of OAB. The activation of the motor fibers can, however, cause unwanted side effects, such as toe twitch or spasm.
As another example, the system can be used to apply electrical stimulation to the tibial nerve to treat sexual dysfunction. In this manner, it is believed that tibial nerve stimulation could be used to treat genital arousal aspects of female sexual interest/arousal disorder by improving pelvic blood flow.
As another example, the system can be applied to the wrist area to provide stimulation to the ulnar nerve and/or median nerve for pain management in carpal tunnel syndrome, hypertension management, and nerve conduction study/nerve injury diagnosis for median/ulnar nerve neuropathy, etc.
The system and/or the device employed by the system can have a variety of implementations. According to one implementation, the electronic medical device (i.e., the electrodes, control unit, wiring, etc.) can be fixed to a garment that is worn by the subject. The garment can be tight or snug-fitting so as to maintain sufficient contact between the subject's skin and can be configured to position the electrodes at locations specific to the peripheral nerves being stimulated. For example, to stimulate peripheral nerves in the area of the foot or ankle, such as the tibial nerve near the medial malleolus as described above, the garment can be in the form of a sock, ankle brace, strap, sleeve, or other like structure. For stimulating peripheral nerves on the leg, the garment can be a brace, strap, or sleeve sized appropriately for lower leg, knee, or upper leg positioning. For knee or ankle positioning, the garment can be configured, e.g., with openings, slots, or interconnected sections, to allow for bending with the joint while maintaining electrode positioning and contact.
Similarly, for stimulating peripheral nerves on the hand, the garment can be in the form of a glove, mitten, hand brace, or sleeve. For stimulating peripheral nerves on the arm, the garment can be a tight/snug fitting brace, strap, or sleeve (e.g., neoprene) that is sized appropriately for lower arm (forearm/wrist), elbow, or upper arm positioning. For wrist and/or elbow positioning, the sleeve can be configured, e.g., via openings, slots, or interconnected sections, to allow for bending with the joint while maintaining electrode positioning and contact.
In keeping with the above, it will be appreciated that the manner in which the electronic medical device can be secured or supported on the subject can vary. It will also be appreciated that the manner in which the electronic medical device is supported is not critical, as long as contact between the electrodes and the subject's skin is maintained, the positions of the electrode on the subject are maintained, and that the aforementioned are achieved in a manner that is comfortable to the subject.
Strap Implementation
The strap 20 implementation of the neurostimulator 10 is advantageous in that it is versatile and can be adapted to secure the neurostimulator to a wide variety of locations on the subject 12. The strap 20 can easily be wrapped around the foot 14 and/or ankle 16, as shown, and can also be wrapped around and secured to any location along the length of the subject's leg 18, either in a single loop or more than one loop, as the length of the strap permits. At the knee, the strap 20 can be wrapped, for example, in a figure-eight style in a manner similar to that illustrated in
Referring to
The neurostimulator 10 includes stimulation electrodes 50 that are arranged in one or more arrays 52 and positioned on an inner surface 36 of the strap 20 at a widened end portion 30 of the strap. The number of stimulation electrodes 50, the area covered by the array 52, the electrode density (i.e., number of electrodes per unit area) in the array, and the distribution or pattern of electrodes within the array all can vary depending on the intended application of the neurostimulator 10. Additionally, the neurostimulator 10 can include more than one stimulation electrode array 52 again, depending on the application. In the example configuration of
In the example configuration of
The neurostimulator 10 also includes dedicated recording electrodes 60 that are arranged in one or more arrays 62 and positioned on the inner surface 36 of the strap 20 spaced from the stimulation electrode array 52. The spacing between the stimulation electrodes 50 and the recording electrodes 60 can be important, as it can be necessary to provide adequate distance between the electrodes so that electrical stimulation signals can be separated or distinguished from responses (e.g., neurological, muscular, neuromuscular, etc.) to those electrical stimulation signals. This facilitates utilizing responses to stimulation sensed by the recording electrodes 60 as feedback in a closed-loop stimulation control scheme, which is described in detail below.
The number of recording electrodes 60, the area covered by the array 62, the electrode density (i.e., number of electrodes per unit area) in the array, and the distribution or pattern of electrodes within the array all can vary depending on the intended application of the neurostimulator 10. Additionally, the neurostimulator 10 can include more than one recording electrode array 62 again, depending on the application. In the example configuration of
In the example configuration of
Referring to
In the example configuration of
Advantageously, the stimulating electrode array 52 can be part of an assembly in which the stimulating electrodes 50 can be mounted on a substrate or housing 56 constructed, for example of plastic. This substrate/housing 56 can itself be secured to the strap 20 (e.g., via adhesives, stitching, or mechanical fastening) to thereby secure the stimulation electrode array 52 to be strap. Forming the stimulating electrode array 52 in this manner facilitates a precise arrangement and spacing of the stimulation electrodes 50 and makes it easy to secure them to the strap 20.
The connector 72 can also be formed as a portion of the housing 56. The connector 72 can be configured to protrude from a side of the housing 56 opposite the stimulation electrodes 50. The connector 72 can, for example, extend through a hole in the strap 20 to position the connector on or extending from the outer surface 38. When the control unit 70 is connected to the connector 72, the strap 20 can be positioned between the control unit and the portion of the housing 56 supporting the stimulator electrode array 52.
The connector 72 can support a plurality of terminals for electrically connecting the control unit 70 to the stimulation electrodes 50 and the recording electrodes 60. Certain terminals in the connector 72 can be electrically connected to the stimulation electrodes 50 by wires or leads that are embedded within the plastic housing material (e.g., via insert molding). Embedding the leads in this manner helps maintain adequate spacing between the conductors, which avoids the potential for shorts in the circuitry.
Other terminals in the connector can be electrically connected to the recording electrodes 60 by wires or leads 66 that are partially embedded within the plastic housing material (e.g., via insert molding) and pass through the housing 56, extending to the feedback electrode arrays 62. Through this configuration, all of the necessary electrical connections to the stimulation and recording electrodes 50, 60 are made when the control unit 70 is installed on the connector 72.
The neurostimulator 10 also includes electrode backing 80 that facilitates safe storage and portability of the system. Fold lines 82, 84 shown in
As shown in
To use the neurostimulator 10, the strap 20 is simply unfolded and the control unit 70 is connected to the housing 56 via their respective connectors 72, 74. The hook and loop fastener 26, 28 can be disconnected, the strap 20 wrapped around the appropriate anatomy of the subject, and the fastener re-connected to attach neurostimulator 10 to the subject. Conveniently, where the neurostimulator 10 is configured for stimulating the tibial nerve in the position illustrated in
Brace Implementation
The brace 120 implementation of the neurostimulator 10 is advantageous in that it is versatile in its ability to position the stimulating electrodes and recording electrodes at different locations on the subject. For example, stimulating electrodes can be positioned on the upper portion 130 of the brace 120 wrapped around the ankle, and recording electrodes can be positioned on the lower portion 150 of the brace wrapped around the foot. This can be especially advantageous for closed-loop neurostimulation of the tibial nerve. In this implementation, stimulating electrodes on the upper portion 130 can be located between the medial malleolus and the Achilles tendon to provide electrical stimulation to the tibial nerve. Recording electrodes on the lower portion 150 can be located on the bottom of the subject's foot, near the flexor muscles (abductor hallucis and the flexor hallucis brevis) for the big toe and can record the EMG signals that result from recruitment of the tibial nerve's motor fibers.
As another advantage, the brace 120 is configured for placement at or about a subject's joint and provides for movement of that joint. While the brace 120 is illustrated as being applied at the subject's ankle joint, it will be appreciated that the brace 120 can also be applied at the knee joint or elbow joint. Additionally, positioning the brace 120 at a joint is not critical, as it can be seen that the brace can be applied at any location along the subject's arms or legs, size permitting.
The construction of the neurostimulator 110 is illustrated in
The upper portion 130 of the brace 120 includes a hook and loop fastener composed of a hook portion 140 and a loop portion 142, which are positioned opposite each other along an upper extent of the upper portion. The upper portion 130 also includes opposite tab portions 144 to which the adjustment tabs 122 (see,
The neurostimulator 110 includes a several of components that are secured or otherwise supported on the brace 120. The securement of these components can be achieved in a variety of manners, such as by adhesives, stitching, mechanical fastening, hook and loop fasteners, or a combination thereof.
The neurostimulator 110 includes stimulation electrodes 170 that are arranged in one or more arrays 172 and positioned on the inner surface 124 of the upper portion 130 of the brace 120. In the example configuration illustrated in
The number of stimulation electrodes 170, the area covered by the stimulation electrode arrays 172, the electrode density (i.e., number of electrodes per unit area) in the arrays, and the distribution or pattern of electrodes within the array all can vary depending on the intended application of the neurostimulator 110. In the example configuration of
In the example configuration of
The neurostimulator 110 also includes recording electrodes 180 that are arranged in one or more arrays 182 and positioned on the inner surface 124 of the lower portion 150 of the brace 120 at a location spaced from the stimulation electrode arrays 172. The spacing between the stimulation electrodes 170 and the recording electrodes 180 can be important, as it can be necessary to provide adequate distance between the electrodes so that electrical stimulation signals can be separated or distinguished from responses (e.g., neurological, muscular, neuromuscular, etc.) to those electrical stimulation signals. This facilitates utilizing responses to stimulation sensed by the recording electrodes 180 as feedback in a closed-loop stimulation control scheme which, again, is described in detail below.
The number of recording electrodes 180, the area covered by the array 182, the electrode density (i.e., number of electrodes per unit area) in the array, and the distribution or pattern of electrodes within the array all can vary depending on the intended application of the neurostimulator 110. In the example configuration of
In another implementation, the neurostimulator 110 can be configured to include MMG sensors (e.g., accelerometers) for sensing muscle movement as opposed to electrical activity. The optional MMG sensors are illustrated in dashed lines at 186 in
In the example configuration of
Referring to
In the example configuration of
Advantageously, each stimulating electrode array 172 can be part of an assembly in which the stimulating electrodes 170 can be mounted on a substrate or housing 176 constructed, for example of plastic. This substrate/housing 176 can itself be secured to the brace 120 (e.g., via adhesives, stitching, or mechanical fastening) to thereby secure the stimulation electrode array 172 to be brace. Forming the stimulating electrode array 172 in this manner facilitates a precise arrangement and spacing of the stimulation electrodes 170 and makes it easy to secure them to the brace 120.
In a manner similar or identical to that of the example configuration of
Again, in a manner similar or identical to that of the example configuration of
Other terminals in the connector can be electrically connected to the recording electrodes 180 by wires or leads 184 that are partially embedded within the plastic housing material (e.g., via insert molding) and pass through the housing 176, extending to the recording electrode arrays 182. Through this configuration, all of the necessary electrical connections to the stimulation and recording electrodes 170, 180 are made when the control unit 200 is installed on the neurostimulator 110.
Referring to
To use the neurostimulator 110, the brace 120 is simply unfolded and the control unit 200 is connected to the housing 176 via the connectors. The hook and loop fasteners 140, 142 and 152, 154 are disconnected, the brace 120 wrapped around the appropriate anatomy of the subject. In
Control Unit Configuration
The control units 70, 200 of the example configurations of the neurostimulator 10, 110 of
The battery protection and charging circuit 224 also marshals power to a high voltage power supply circuit 230, a digital power supply circuit 232, and an analog power supply circuit 234. The high-voltage power supply circuit 230 is used to provide a stimulation compliance voltage to the output stage's current sources and sinks. Since this device is a transcutaneous stimulator, it can require a compliance voltage in the range of about 40-200 V or more in order to provide the necessary current to stimulate the tibial nerve. For this embodiment, a compliance voltage of 120 volts is used for the compliance voltage.
A radio controller 240, such as a Bluetooth® or Zigbee® radio controller, provides a communication input to the microcontroller 220 for functions such as programming the control unit 70, 200, uploading/downloading data, and monitoring/controlling the neurostimulator 10, 110 during use. The radio controller 240 could, for example, pair the microcontroller to an enabled device, such as a smartphone, tablet, or computer, executing software that enables the user to monitor or otherwise control the operation of the neurostimulator 10, 110. The microcontroller 220 controls the operation of indicators 242, such as LEDs, that indicate the state or condition of the control unit 70, 210. The microcontroller 220 can control an accelerometer 244, which can provide input to determine whether the neurostimulator 10, 110, and thus the subject, is moving or at rest.
The microcontroller 220 is responsible for controlling the stimulation output, measuring the electrode impedance, and processing the EMG response. The microcontroller 220 runs software for performing these functions, including decision-making algorithms to allow the device to provide the desired therapy. The microcontroller 220 controls the operation of an amplitude control circuit 250, a timing control circuit 252, and a digital-to-analog converter (DAC) 254. By “circuit,” it is meant that these functions can be implemented in any desired manner, e.g., through discrete components, integrated circuits, or a combination thereof. The amplitude control circuit 250, timing control circuit 252, and DAC 254 drive a stimulator output stage 260, which provides stimulator output signals (e.g., pulse-width-modulated “PWM” output signals) to one or more analog output switches 262. The output switch(es) 262 are operatively connected to a port 280 comprising a plurality of terminals (E1-E8 in
The microcontroller 220 receives electrode impedance values via an impedance measurement circuit 264 that is operatively connected to the stimulator output stage 260. The microcontroller 220 also receives electrode feedback values (e.g., F-wave and M-wave values) via an analog front end 270 that is operatively connected to one or more analog input switches 272. The input switch(es) 272 are also operatively connected to the terminals/port 280 and can thereby receive feedback from the recording electrodes 60, 180 that facilitates connecting the control unit 70, 200 to the stimulator and recording electrodes, for example, via the leads 66 (see,
The impedance measurement circuit 264 allows for measuring the impedance of the electrodes. It is important to measure the impedance often, in case one or more of the electrodes begins to lift from the skin. There are two potential hazards related to electrode lifting that should be mitigated. First, if an electrode is partially lifted from the skin, the surface area of the electrode that is in contact with the skin is reduced and the current density of the stimulation current is increased, which can be unsafe. Second, if an active electrode is completely lifted from the skin, a brief but large amount of energy can be delivered to the tissue when the electrode makes contact with the skin, which can result in pain.
Electrode impedances measured via the impedance measurement circuit 264 can also be used as an additional input for a closed-loop stimulation optimization algorithm.
The stimulator output stage 260 provides the current to the stimulating electrodes via the output switch 262. Each channel of the output stage includes a current source and current sink, which allows each channel to provide either a positive or negative current to the tissue through the corresponding stimulation electrode(s) 50, 170. In this configuration, each current source and sink can have independently programmable amplitude control 250 and timing control 252, which provides the capability to “steer” the current applied via the stimulation electrodes 50, 170, as described below. The programmable range can vary depending on the application, and is selected to be capable of achieving the desired nerve recruitment. In an example configuration, the current sources can have a programmable range from zero to +20 milliamperes (mA), and the current sinks can have a programmable range from zero to −20 mA.
As shown in
Control Overview
According to one example implementation, the neurostimulator 10, 100 described above can control the application of stimulation therapy according to two general phases: nerve localization and stimulation delivery. These two phases work synergistically to provide the functionality set forth in the following paragraphs.
During the nerve localization phase, the target peripheral nerve structure, e.g., the tibial nerve, is localized when the neurostimulator 10, 100 is donned and activated. In the nerve localization phase, the neurostimulator 10, 100 implements a process in which the following functions are performed:
Ramping up stimulation energy across various electrode patterns.
Monitoring EMG response after each stimulation pulse.
Determining the electrode pattern and stimulation parameters that optimally activate the target peripheral nerve.
During the stimulation delivery phase, electrical stimulation is delivered to the target peripheral nerve structure using the electrode pattern(s) and stimulation parameters determined during the nerve localization phase. In the stimulation delivery phase, the neurostimulator 10, 100 implements a process in which the following functions are performed:
Deliver stimulation pulses to the target peripheral nerve.
Continuously optimize the delivery of stimulation pulses, which includes:
Monitoring EMG response after each stimulation pulse.
Monitoring electrode impedance.
Adjusting either the electrode pattern (current-steering) or stimulation energy to optimize recruitment of the tibial nerve.
Automatically stopping stimulation at the end of the therapy session.
The nerve localization and stimulation delivery phases are described in more detail in the following sections.
Nerve Localization
In practice, the control unit 110 can be programmed with a set of electrode patterns that identify which stimulation electrode 50, 170 in an electrode array 52, 172 are active, and also the polarity or type, i.e., anode (+) or cathode (−) assigned to the electrode.
The neurostimulator 10, 110 can be configured to perform a nerve localization routine to determine which of the electrode patterns should be utilized on a subject. In the example configuration of
In the example configuration of
The purpose of using an array for stimulation (as opposed to a single pair of electrodes) is to create an optimized stimulation field for recruiting the target (e.g., tibial) nerve. If the stimulation field is too small, the nerve will not be recruited and therapy will not be delivered. If the stimulation field is too large, too many motor neurons will be recruited resulting in undesired effects, such as pain, twitching, or muscle spasm. In order to optimize the stimulation field, the ability to steer current using multiple electrodes if preferred. For example, electrode pattern 8 assigns electrodes E3 and E4 as anodes and electrodes E7 and E8 as cathodes. Viewing the arrangement of these electrodes 50, 170 on the array 52, 172, it can be seen that the use of this electrode pattern could be effective on a nerve path that passes directly adjacent or between these electrode pairs.
By selecting the appropriate stimulation electrodes 50, 170 from the stimulation electrode arrays 52, 172, and varying the amplitude and polarity of the current applied via the selected electrodes, the electric field applied to the subject can be shaped so that the current is steered to the target nerves. By shaping the field, the neurostimulator 10, 100 can automatically adjust to day-to-day donning and placement variability for a given subject. Current steering also allows the neurostimulator 10, 100 to work across a subject population with wide anatomical variation, for example providing a shallow field for subjects with nerves that are superficial to the skin, or a penetrating field for subjects with nerves that are deep. In the illustrated example configurations, the stimulation electrode arrays 52, 152 include six electrodes. Any number of stimulation electrodes greater than one can be used. In general, the “field steering” capability of the neurostimulator 10, 100 increases with the number of stimulating electrodes 50, 170 that are included.
Because there will be session-to-session variability in the location of the stimulating electrode array 52, 172 due to the don/doff process, as well as variability in skin/tissue impedance, providing open-loop stimulation applying rigid pre-programmed stimulation parameters could be disadvantageous, often providing too little or too much stimulation energy to recruit the nerve. Advantageously, the nerve localization algorithm is executed at the beginning of each therapy session to determine which of the preprogrammed electrode patterns will be most effective.
It should be noted here that, the process 300 is a closed-loop algorithm that utilizes feedback recorded via the recording electrodes 60, 180 to make determinations and/or adjust settings. As such, the process 300 relies on utilization of the feedback to determine which of the electrode patterns effectively achieves nerve recruitment. Specifically, the process 300 relies on feedback from the recording electrodes 60, 180 to provide indication of EMG response feedback. Alternatively, the process 300 can rely on accelerometers to provide MMG response feedback.
Referring to
For example, in the example of
To avoid interfering with stimulation and EMG measurement, the integrity check at step 302 can be completed in a short amount of time, such as 25 milliseconds or less. Also, the impedance measurement can be conducted so as to cause little or no sensation in the subject's skin. Therefore, the excitation current for performing the integrity check should be low-amplitude, such as 1 mA or less. For the integrity check 302, the impedance value at each electrode is not critical. Instead, determining whether the impedance is below a certain threshold is adequate.
Additionally, conditions other than high or low impedance can be determined in this integrity check. For example, indicators such as dry/wet contact checks, whole/brittle/fractured contact checks, contact surface area checks, and contact reflectance checks can be made during the connectivity evaluation. Sensors, such as don/doff, stretch, strain, bending or contact sensors (via electrical, optical or mechanical means) can also be used for conducting the connectivity evaluation. These sensors could also be incorporated into a buckle, clasp, snap, hook/eye or zipper feature.
Once the integrity check is performed, the process 300 proceeds to step 304 where the first electrode pattern (that hasn't been eliminated by the integrity check) is loaded. The process 300 then proceeds to step 306 where the neurostimulator 10, 110 generates stimulation pulse(s) using the electrode pattern loaded in step 304. The process 300 proceeds next to step 310, where a determination is made as to whether the stimulation pulses generated at step 306 elicited an EMG response, i.e., feedback measured via the recording electrodes. Step 310 can additionally or alternatively determine whether there is a MMG response where the feedback devices include accelerometer(s).
If, at step 310, EMG (or MMG) is not detected, the process 300 reverts to step 314, where a new electrode pattern is loaded. The process 300 then proceeds to step 306, as described above. If, at step 310, EMG (or MMG) is detected, the process 300 proceeds to step 312, where the electrode pattern is added according to pattern selection rules. The process 300 then proceeds to step 316, where a determination is made as to whether the current electrode pattern is the last electrode pattern in the list.
The pattern selection rules at step 312 for adding an electrode pattern can be defined to prioritize electrode patterns identified as being the best suited to recruit the target nerves. These pattern selection rules may be implemented as follows:
If one pattern is significantly better than the others (e.g., as determined from the EMG data, see below), that pattern should be used as the primary pattern moving forward.
If two or three patterns are roughly equivalent, any one of the patterns can be used as the primary pattern. Moving forward, this pattern can be switched to other ones if the nerve recruitment displayed by the current primary pattern begins to diminish.
If the nerve recruitment for a particular pattern begins to diminish and increasing the stimulation parameters does not fix the problem, similar patterns can be re-introduced to the algorithm.
If, at step 316, it is determined that the current electrode pattern is not the last pattern in the list, the process 300 reverts to step 314, where a new electrode pattern is loaded. The process 300 then proceeds to step 306, as described above. If, at step 316, it is determined that the current electrode pattern is the last pattern in the list, this indicates that the pattern list is complete. The process 300 proceeds to step 320 where the stimulation parameters for the electrode patterns in the pattern list are optimized. At step 320, the stimulation parameters (e.g., frequency, amplitude, pattern, duration, etc.) are updated to optimize the nerve recruitment for each pattern. The process 300 then reverts back to the initial step at 302 and proceeds as described above. If the recruitment for a given electrode pattern improves, the stimulation parameters are kept. If not, they revert back to previous values. This process repeats itself until the pattern list is filled with electrode patterns optimized for nerve recruitment.
From the above, it will be appreciated that the nerve localization process 300 determines which of the electrode patterns to utilize and which to discard for any given stimulation therapy session, and then optimizes the stimulation parameters for the utilized patterns. The execution of this process 300 is fast. During execution, the neurostimulator 10, 110 applies stimulation therapy pulses via the stimulating electrodes 50, 170 and monitors for EMG responses via the recording electrodes 60, 180 after each pulse.
The analog front end circuit 270 can replace traditional EMG measurement circuitry such as a filter, amplifier, rectifier, and/or integrator. The control unit 110 utilizes the analog front-end circuit 270 to sample the recording electrodes at a predetermined sample rate, such as 1,000-8,000 samples per second. The EMG sampling window will begin after the stimulation pulse is finished, and the window will last for a predetermined brief period, such as 8-90 milliseconds. The resulting EMG data, comprised of M-wave or F-wave or both, will be analyzed using a Fast Fourier Transform (FFT) technique that clearly shows if EMG is present.
To execute the process 300 of
For each of the four recorded response scenarios,
The neurostimulator 10, 110 can apply stimulation therapy using an open-loop control scheme, a closed-loop control scheme, or a combination of open-loop and closed-loop control schemes, depending on the control algorithm programmed into the microcontroller 220. For open-loop control, the control units 70, 200 can apply electrical stimulation via the stimulation electrodes 50, 170 according to settings (frequency, amplitude, pattern, duration, etc.) without regard to any feedback measured via the recording electrodes 60, 180. This is not to say that feedback is not measured, just that, in an open-loop control scheme, the feedback is not used to inform or control the algorithm executed by the microcontroller 220 to control the application of stimulation therapy. In a closed-loop control scheme, the neurostimulator 10, 110 implements a control algorithm in which feedback from the recording electrodes 60, 180 informs and helps control the application of stimulation therapy.
The process 400 begins at step 402, where the impedances of the recording electrodes 60, 180 are checked. If, at step 404, it is determined that the recording electrode impedances are too high (e.g., resulting in unavailable or unreliable feedback), the process 400 then shifts to open-loop mode (see dashed lines) and proceeds to step 412, where a delay is implemented. The purpose of delay 412 is to assist in maintaining a constant stimulation period, meaning that the duration of delay 412 should be equal to the duration of closed-loop step 406. After completing delay 412, the process 400 proceeds to step 414, where the stimulation electrode impedances are checked.
At step 404, if the impedances of the recording electrodes are acceptable, the process 400 remains in closed-loop mode and proceeds to step 406, where samples are obtained via the recording electrodes to check for significant noise or voluntary EMG responses. At step 410, if noise or EMG are present, the feedback is considered unreliable and the process 400 shifts to open-loop mode and proceeds to step 414. At step 410, if significant noise or voluntary EMG is not present, the feedback is considered reliable and the process 400 remains in closed-loop mode and proceeds to step 414.
At step 414, regardless of whether the process is in open-loop mode or closed-loop mode, the impedances of the stimulation electrodes 50, 170 are checked. At step 416, if the stimulation electrode impedances are acceptable, the process 400 proceeds to step 420 and the neurostimulator 10, 110 generates stimulation pulses, which are applied via the stimulation electrodes using the optimal electrode pattern, as determined by the nerve localization process 300 (see
At step 424, the process 400 implements a pre-recording delay to allow time for the electrical stimulation applied at step 420 or 422 to elicit an EMG response. As discussed above, these delays can be relatively short, so the delay at step 424 can, likewise, be short, e.g., 5 ms or less. If the process 400 is in open loop mode, it proceeds to step 432, where a further delay is implemented. This delay 432 should match the duration of closed-loop steps 426 and 430 so that a constant stimulation period is maintained. If the process 400 is in closed-loop mode, it proceeds to step 426 and checks for feedback via the recording electrodes 60, 180. The process 400 then proceeds to step 430, where any detected EMG feedback signals are recorded and analyzed.
At this point, regardless of whether the process 400 is in open-loop mode (step 432) or closed-loop mode (step 430), the process proceeds to step 434, where a determination of whether the number of stimulation pulses applied in the current therapy session has reached a predetermined number (N). If the predetermined number (N) of pulses have not yet been applied, the process proceeds to step 436, the stimulation amplitude is maintained at the current level, and the process 400 reverts back to step 402, where the impedance of the recording electrodes is checked and the process 400 repeats. If, at step 434, the predetermined number (N) of pulses has been reached, the process 400 proceeds to step 440.
At step 440, if the process 400 in open-loop mode, the process proceeds to step 442, the stimulation amplitude is maintained at the current level, and the process 400 reverts back to step 402, where the impedance of the recording electrodes is checked and the process 400 repeats. At step 440, if the process 400 is not in open-loop mode (i.e., is in closed-loop mode), the process proceeds to step 444, where a determination is made as to whether the EMG recorded at step 430 is below a predetermined window, i.e., below a predetermined range of acceptable EMG values. If the EMG is below the predetermined window, the process 400 proceeds to step 446, where the stimulation amplitude is increased for the next pulse, if permitted. The process 400 then reverts back to step 402, where the impedance of the recording electrodes is checked and the process 400 repeats with the increased stimulation amplitude.
If, at step 444, the EMG is not below the window, the process 400 proceeds to step 450 where a determination is made as to whether the EMG is above the predetermined window. If the EMG is above the predetermined window, the process 400 proceeds to step 452, where the stimulation amplitude is decreased for the next pulse. The process 400 then reverts back to step 402, where the impedance of the recording electrodes is checked and the process 400 repeats with the decreased stimulation amplitude. If, at step 450, the EMG is not above the predetermined window, the EMG is determined to be within the predetermined window and the process 400 proceeds to step 454, where the stimulation amplitude is maintained at the current level for the next pulse. The process 400 then reverts back to step 402, where the impedance of the recording electrodes is checked and the process 400 repeats.
As discussed previously, stimulation of nerves, such as the tibial nerve 502, can provide therapeutic benefits to multiple conditions, with one example being overactive bladder (OAB). For consistent therapy, monitoring muscle activity induced by the activation of neuromuscular junction is important. For example, the neurostimulator 10, 110 described above with reference to
The manner in which the neurostimulators 520, 550 are supported on the subject, i.e., worn, can vary. For example, the neurostimulators could be configured in the form of a sock that fits over the subject's foot and ankle, or in the form of a sleeve that slides over the foot/ankle, leaving the toes exposed. The support structure for positioning the neurostimulator components on the subject can have any configuration suited to place the components at the desired location on the subject.
The neurostimulators 520, 550 include recording electrodes 524, 554, respectively, that have an elongated profile configured to extend laterally across the longitudinal muscle groups of the foot (see,
The neurostimulators 520, 550 can be configured so that the elongated recording electrodes 524, 554 span over the whole width of the bottom of the foot 500. This is shown in
When more than one muscle is recruited, it has been confirmed that there is no adverse impact on the integrity of the combined feedback signal received by the elongated electrodes 524, 554 due to their simultaneous recruitment. This feedback signal is further analyzed using particular signal processing and noise reduction techniques. The elongated electrodes 524, 554 can therefore advantageously improve the recording function of the neurostimulators 520, 550.
To promote good, reliable contact between the electrodes and the subject's foot, the neurostimulators can include a compliant member that facilitates forming the electrodes to the contour of the foot. This is shown by way of example in the magnified section view detailed in
Integrated Wearable Device with Built-In Stimulating and Recording
The neurostimulators described herein, including the neurostimulators 520, 550 of
The neurostimulators 520, 550 have integrated constructions in which the electrodes and traces are embedded into their respective garments 522, 552, thus eliminating a need for external wiring, adhesive or other such mechanisms that can limit the usability or reliability of the garment. According to one implementation, the stimulation electrodes, recording electrodes and traces are all fabricated as a single part in which the electrically conductive and insulating components are formed as one or more layers of electrically conductive materials, such as a flexible printed circuit, that is supported on a flexible substrate.
This prefabricated part may than be attached to the garment using a multiplicity of processes, one such example being thermal pressing. In this construction, the substrate supporting the electrical components can comprise a thermal adhesive that facilitates the thermally pressed attachment. Alternatively, the conductive and insulative layers can be directly imparted on the garment using processes such as spraying or deposition.
The electrodes have conductive material exposed to ensure good contact with patient body. The traces may be made from a conductive material printed on a non-conductive sheet and then adhered to the garment. However, an electrical contact between the traces and human body is undesirable, and prevented by means of insulation, which could be the non-conductive sheet, or may include an additional layer of insulation material. The garment may be made of a material that provides sufficient flexibility, is compatible with human body and allows for electrode printing. An example of such garment material may be neoprene. Thus, a system having all electrodes and traces within a single component minimizes any connectivity losses, compatibility or dimensional tolerancing challenges.
Advantageously, these constructions have the ability to flex during normal use of the garment when the fabric is stretched. To facilitate stretching, the traces can be configured to have a curved/bent/waved appearance, as shown with the traces 558 in the example configuration of the neurostimulator 550 of
According to another aspect of the invention, the neurostimulators described herein can be configured to automatically detect the foot, i.e., right or left, upon which the neurostimulator is worn. The neurostimulator is configured to be worn on either foot. Regardless of the foot upon which the neurostimulator is worn, the recording electrodes are positioned across the foot in the manner shown in
Advantageously, since the recording electrodes 524, 554 extend across the foot (see
The strap neurostimulator 550 (
The neurostimulators 520, 550 are configured to record the evoked muscle response to the activation of tibial nerve as a phase relationship (or time delay) between the stimulation signal and the EMG response. When the garment is moved from one foot to the other, this phase relationship is altered, thus providing a unique differentiator between the two feet. The phase relationship is shown in
In another configuration of the neurostimulator 520, 550, the need to switch electrode polarity in response to the foot onto which the device is fitted can be avoided. In this configuration, the neurostimulator 520, 550 can be configured to include redundancy in stimulation electrodes. For the H-brace neurostimulator 520, the redundancy is shown in the left/right electrodes 530, 532. For the strap neurostimulator 550, the redundancy can be implemented by altering the pin configuration to selectively chose a pair (or group) of electrodes. To make this determination, the controller is configured to alter the pin configuration of the neurostimulator to alter the measured impedance between the stimulation electrodes. The left/right foot determination is made by finding the impedance between the electrodes that is indicative of the foot location. In one implementation, the expected impedance can be about 5k-ohm.
In a further configuration, the spacing between the cathode and anode may be deliberately made unequal between Left and Right side of the garment. This will result in two differences. First, the overall feedback signal, including phase and amplitude, will be different because the response is dependent on stimulation electrode configuration and spacing. Second, this will cause the impedance between the two electrodes to be different. Either of these values can be measured during the therapy session, and thus can then be used to determine which foot of the subject.
As discussed previously, the neurostimulators 520, 550 have wide therapeutic applications, such as pain management and bladder control. According to these treatment methods, a known amount of charge is applied through either a pair or multiplicity of electrodes attached to the subject's body. Most systems determine the amount of charge using the amplitude of the voltage or current applied, or through the duration of the pulse, or pulse width, of the voltage of current applied. All these methods have limitations in terms of therapy range, energy usage and in accounting for different patient sensation or anatomical response.
According to another feature, the neurostimulators 520, 550 can be configured to control the application of stimulation therapy in a manner that compare the amplitude of the stimulation signal to the pulse width, to provide a optimal combination of therapy, energy use, patient sensation and ease of use. This can be implemented in both closed-loop, with where stimulation is modulated based on an evoked electrical response, or in open-loop where no response is recorded. Also, the neurostimulators 520, 550 can be configured for current-control or voltage-control. Because of this, it should be understood that, when the term ‘stimulation signal’ is used herein, it can be associated with electric current or voltage.
In one example configuration, a method for determining optimal charge for neurostimulation involves applying stimulation within a range of pulse widths that are defined by both the subject's tolerance as well as the threshold for evoking a response. This is shown in
After the initiation of therapy and over the course of time, a need to change the therapeutic regime can arise. this can result, for example, from a patient's tolerance changing over time, device characteristics changing over time, or the body's response changing as a result of therapy. Accordingly, the applied current amplitude can be adjusted and a new corresponding range of pulse width defined. This is shown in the example of
As another example configuration, stimulation can be executed within an operating zone defined by a range of pulse widths and range of current amplitudes. This is shown in
Stimulation of nerves has wide therapeutic applications, such as pain management or bladder control. For best possible patient outcomes, it is important to determine the optimal stimulation parameters that provide therapeutic benefits, while ensuring no patient discomfort that could lead to non-compliance. Accordingly, a method for determining these optimal stimulation parameters utilizes multiple factors, including patients' muscle and sensory responses. According to the method, the therapy target is based on the individual patient's response induced by the stimulation, therapeutic needs and tolerance threshold, while at the same time ensuring the therapeutic window never extends beyond any of these limits.
According to this method, the closed-loop system is employed that detects and quantifies the stimulation evoked response, such as EMG or nerve response, when a stimulation is applied. The lower threshold of therapeutic window is defined at the level at which the evoked response is detected. This is based on two factors, one being a physical confirmation of recruitment of the corresponding nerve to ensure system operates as intended, and second being the ability to continuously adjust the stim based on the evoked response. The upper threshold is defined by the sensory feedback, or at a level that a patient can comfortably tolerate for a duration of a typical therapy session.
The upper (discomfort) and lower (detection) thresholds define the operating range and also define the optimal stimulation therapy that is targeted for a specific patient. This patient-specific target therapy is linearly interpolated between the upper and lower thresholds in a manner that is determined by the clinical need for a certain indication. Examples of these interpolated target therapy ranges are illustrated in
Alternative ranges can be selected, for example, to increase the system output. To achieve this, the lower limit can, be defined at a higher percentage of the range, such as 75% of the range. In this example, the upper range can be set accordingly, such as at 85-90%. As shown in
The examples of
According to the method 620 of
The method 660 addresses the nonlinearity of the evoked biological responses makes it difficult to use as feedback for controlling for a neural stimulation device. Implementing the method 660, the neurostimulator is adapted to provide effective feedback control during neural stimulation with or without a presence of a biological response. This helps maximize the therapy during application of neural stimulation. The methods 660 utilizes the presence of an evoked biological response, the strength of the evoked response, and voluntary input from the user/subject/patient to modulate the control signal in a closed-loop stimulation application.
Biological responses are not always linear with provided stimulation: higher stimulation doesn't always generate higher biological responses. “Biological responses,” as used herein, refers to any stimulation evoked biological change, i.e., physiological signals, biochemical responses in the body, biomechanical responses, etc. Accordingly, the algorithms implemented by the method 660 should treat the presence of the biological responses, and the strength of the biological responses separately, and according to the general guidelines:
No biological response—Open loop stimulation control within the tolerable stimulation range.
Biological response evoked—Use the frequency of response appearance within a predefined time window as the therapy level, i.e., within a 1 second time window. The appearance of the evoked biological responses should be at least 50% among all the stimulus delivered.
Biological response evoked—Identify the presence of the response, calculate the strength of the response, set x % (include 0%) higher of this strength level as the default therapy level. Patient or physician can set new strength level as the therapy level as needed.
Combine multiple types of biological responses.
Based on the user/subject/patient subjective feelings, voluntary input to control the delivery of neural stimulation can be given, i.e.:
Intentional voluntary input:
User input commands through a device hardware interface or software application, i.e. a physical button pressing on the device, or command input from the app.
a voice command.
Unintentional voluntary input:
User voluntarily generate artifact, noise or voluntary biological response (e.g. from wincing in pain) that manifests in the recording sensors.
User voluntary verbal response (e.g., shout, scream) of the unpleasant stimulation. The device recognize its using its built-in microphone and voice recognition technology.
The method 660 can be implemented by a neurostimulator, which applies stimulation therapy via one or more stimulation electrodes, and monitors a biological response, such as an EMG response, via one or more receiving electrodes. The method 660 can, for example, be implemented in any of the neurostimulators disclosed herein.
At step 664, stimulation therapy is delivered via a neurostimulator. At step 666, a determination is made as to whether a response, such as an EMG response, is detected. If no response is detected, the method 660 proceeds to step 662, where the neurostimulation is delivered in open-loop control, i.e., without feedback. The method 660 reverts back to step 664, where stimulation therapy is delivered, and continues to step 666 to determine whether a response is detected. As long as there is no detected response to the stimulation, the method 660 continues to deliver stimulation therapy under open-loop control.
At step 666, if a response, such as an EMG response, to the stimulation is detected, the method 660 proceeds to step 668, where the response detection rate is calculated, then to step 670 where the control regime is determined based on the detection rate. The control regime can be response appearance control, response strength control, or response appearance+strength control. Under response appearance control, the method 660 proceeds from step 670 to step 672 where a determination is made as to the response detection rate that will be the setpoint for closed-loop control. The method 660 proceeds to step 674 where closed-loop control of the stimulation is performed to maintain the X % of the detection rate determined in step 672, where X can be 100 or less. Stimulation parameters, i.e., current amplitude and/or pulse width, are modulated to maintain the detection rate identified in step 672.
Under response strength control, the method 660 proceeds from step 670 to step 680, where a response strength setpoint is calculated. This setpoint is used for closed-loop control. The method 660 proceeds to step 682 where closed-loop control of the stimulation is performed to maintain the response strength at a certain level, Z % greater than the response strength setpoint calculated in step 672, where Z can be zero or greater. Stimulation parameters, i.e., current amplitude and/or pulse width, are modulated to maintain the response strength at the setpoint.
Under response appearance+strength control, the method 660 proceeds from step 670 to step 676, where Y % of the response detection rate is determined as the minimum detection threshold, where y can be 100 or less. At step 678, the minimum detection threshold is used as a setpoint to maintain Y % of the response detection rate under closed-loop stimulation control. The method 660 proceeds to step 680, where a response strength setpoint is calculated. This setpoint is implemented in closed-loop stimulation control at step 682, where the control is performed to maintain the response strength at the certain level, Z % greater than the response strength setpoint calculated in step 672, where Z can be zero or greater. Thus, under the response appearance+strength control scheme, stimulation is modulated under closed-loop control to maintain both a response detection rate and a response strength.
Referring to
The data used at step 652 can be recorded stimulation history, the elicited muscle responses, and the effect the stimulation had on the patient. For example, an overactive bladder patient can use the controller to record a bladder diary that forms a portion of the information/data at step 646. As such, the data transmitted to the cloud/server 650 can include a real-time stimulation history or a quantitative summary of each therapy session.
Once this information is uploaded and available, a portal uses informatics to correlate the three main characteristics: the stimulation profile (e.g., current amplitudes, voltages, pulse profiles), the feedback history (e.g., EMG data), and the patient diaries. The algorithms implemented at the informatics stage 652 use this data to assess the effect of stimulation on the feedback signal and system efficiency. As this data is collected over a larger period of time and over a larger population of patients, it can be used for monitoring patient compliance, usability and efficacy. This information can be used to optimize therapy for each individual patient and thus improving patient outcomes.
According to another example implementation of the system, method, and apparatus disclosed herein, an electrical neurostimulation system can include a bilateral stimulation system that implements a garment with a bilateral electrode configuration that fits both right and left feet. Current designs of foot-worn electrical neurostimulation garments distinguish between left and right foot. These designs are not optimal as they require a separate design and manufacturing process for the different garments.
The garment utilized to implement the bilateral stimulation system, method, and apparatus can have various configurations. The garment can, for example, have a brace configuration similar or identical to that shown in
The manner in which the neurostimulator 700 is supported on the subject, i.e., worn, can vary. For example, the neurostimulator could be configured in the form of a sock that fits over the subject's foot and ankle, or in the form of a sleeve that slides over the foot/ankle, leaving the toes exposed. The support structure for positioning the neurostimulator components on the subject can have any configuration suited to place the components at the desired location on the subject, as shown in
The neurostimulator 700 includes stimulation electrodes 710 and recording electrodes 720. The recording electrodes can be configured and arranged in any of the manners disclosed with reference to any of the configurations disclosed herein. In the example configuration of
The stimulation electrodes 720 of the neurostimulator 700 have a bilateral electrode configuration that enables bilateral neurostimulation of the target peripheral nerve with a garment that can fit and accommodate right foot and left foot implementations. The neurostimulator 700 can implement any of the closed-loop and/or open-loop neurostimulation control schemes disclosed herein, along with any of the specific features, such as right/left foot detection. This configuration is advantageous in that it allows for a one-device-fits-all approach. Advantageously, this also reduces the design, testing, and manufacturing complexities associated with specific foot configurations.
Referring to
Current garment designs include two stimulation electrodes on one side of the ankle. These two electrodes, along with a connector work together to apply stimulation to activate the tibial nerve. If the garment is being used on another foot, the electrode configuration needs to be reversed, with the two electrodes and connector on the opposite side of the garment. This is referred to herein as an “ipsilateral design.” For example, the neurostimulator 520 of
The bilateral neurostimulation system, method, and apparatus disclosed herein and implemented via the neurostimulator 700 of
The bilateral design of the neurostimulator 700, when worn, produces a contralateral positioning of the stimulation electrodes 710, i.e., positions the stimulation electrodes on opposite sides of the foot/ankle, in the manner shown in
The electrical field created between the stimulation electrodes 710 in the contralateral electrode configuration of the bilateral design extends across the foot, i.e., from the medial side to the lateral side (or vice versa, depending on how the electrodes are energized), as indicated generally by the flux lines (dashed lines) shown in
The fact that the bilateral design of the neurostimulator 700 implementing the contralateral electrode configuration produces an electrical stimulation field that penetrates across the foot and thereby helps ensure tibial nerve recruitment provides some liberty in selecting the configuration and operation of the stimulation electrodes 710. An example is the identification/selection of which of the stimulation electrodes 710 is the anode and which is the cathode. The bilateral positioning of the stimulation electrodes 710 helps ensure that the tibial nerve fibers will be activated regardless of which side is the anode and which side is the cathode. Therefore, the neurostimulator 700 can apply anodic or cathodic stimulation to the tibial nerve from either side of the nerve, which lends flexibility to the system. This also allows for determining which method of application renders the most effective stimulation results.
A stimulating electrode can act as an anode (+, source of current) or a cathode (−, sink of current). Experimental data has shown that cathodic stimulation elicits neural responses (action potentials) more readily than anodic stimulation. Given the same stimulation strength or energy, cathodic stimulation elicits neural responses more readily than anodic stimulation. The power level (amplitude) required to elicit such a response through anodic stimulation can, for example, be several times that required of cathodic stimulation.
The effectiveness of a stimulation signal in recruiting a nerve is indicated or related to the second derivative of electrical potential of the signal. This is shown in
This is not to say that cathodic stimulation is necessarily more desirable than anodic stimulation. Because, however, with all things being equal, cathodic stimulation has been shown to require less power/energy, it has naturally evolved as the primary arrangement. The bilateral configuration of the neurostimulator 700, positioning the electrodes on opposite sides of the foot and the tibial nerve, optimizes the effectiveness of all stimulation fields, cathodic or anodic, because the field acts laterally, as described above, which helps ensure a high probability of nerve recruitment, as long as the strength of the field is sufficient.
As described herein previously, the effects of tibial nerve stimulation depend on the stimulation parameters, i.e., the amplitude, frequency, and waveform characteristics, i.e., pulse parameters, of the stimulation pulses. The effects of tibial nerve stimulation can also depend on properties of the stimulated tissue, such as the distribution and orientation of the nerve axons, tissue, structures, fluids, etc. surrounding the nerve. Because of this, it can be difficult to determine which electrode configurations and/or arrangements will be most effective. As a result, determining the electrode configurations and/or arrangements that prove to be most effective for a particular subject can be a matter of trial-and-error. Advantageously, the bilateral design of the neurostimulator 700 facilitates identifying the ideal configuration/arrangement of the stimulation electrodes 710 because the arrangement helps ensure that stimulation energy will reach the tibial nerve.
The bilateral design of the neurostimulator 700 allows it to have no assigned role for anode and cathode. The controller 730 will assign the cathode/anode identity, which can be switched back and forth. Thus, for example, during one stimulating pulse, one stimulation electrode 710 can be the cathode positioned medially and the other the anode positioned laterally. During next stimulating pulse, the cathode/anode designation can be reversed. This cathode/anode electrode switching can be done in any pattern and order, e.g., every pulse, every other pulse, every five pulses, etc.
Because the neurostimulator 700 is ambidextrous and can fit the right or left foot, the cathode/anode identifications for the stimulating electrodes 710 varies depending on the foot upon which the neurostimulator is worn. One example configuration, the identity of the foot—right or left—can be determined automatically, as described above. In another example configuration, the user can select which foot the stimulation is being applied. If, for example, the device is used on the right ankle, user will selected the ‘Right Foot’ on the patient interface, then one stimulation electrode 710, medial or lateral, can be the cathode and the other can be the anode. The bilateral design of the neurostimulator 700 is therefore advantageous because it is designed for both feet, and the user doesn't need to 1) purchase two devices and 2) be concerned with which foot the device is worn upon.
Additionally, the bilateral construction and contralateral operation of the neurostimulator 700 can be less complicated because the stimulation electrodes 710 on both sides are used in every instance of operation. Advantageously, the neurostimulator 700 does not require any switching between right/left electrode pairs, such as in the example configuration of
While aspects of this disclosure have been particularly shown and described with reference to the example aspects above, it will be understood by those of ordinary skill in the art that various additional aspects may be contemplated. A device or method incorporating any of the features described herein should be understood to fall under the scope of this disclosure as determined based upon the claims below and any equivalents thereof. Other aspects, objects, and advantages can be obtained from a study of the drawings, the disclosure, and the appended claims.
This application claims priority from U.S. Provisional Patent Application Ser. No. 63/307,702, filed Feb. 8, 2022, the entirety of which is hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63307702 | Feb 2022 | US |
