Patent Application
20200368524
The present invention relates to the insertion of neural implants which contain one or more electrodes arranged on one or more penetrating members, such as shanks, that are inserted into neural tissues for the purpose of establishing a neural interface through which to directly record and/or to stimulate neural activity. More specifically, the invention relates to a system to aid the insertion of neural implants through application of high frequency micro-vibration to the penetrating member(s) of the probe or electrode array to reduce the forces required to penetrate the tissue. The system also includes target stabilization mechanisms utilized during insertion for precise implant placement.
Neural implants, such as chronically implanted microelectrode arrays designed to interface with neural tissue hold great potential for revolutionizing treatment of a range of medical conditions. Applications of neural implants include neural-based control of prosthetic limbs by amputees, brain-machine interfacing for paraplegics, selective ablation and/or inactivation of problematic neural pathways, or control or enhancement of organ function. Programs like SPARC, the BRAIN Initiative, and BrainGate are bringing new neuroprosthetic devices to patients, and researchers predict that neural implants will be more widely implemented in humans in the next 10 years. Non-penetrating neural implant electrode arrays such as EEG electrodes and nerve cuffs have seen increased clinical application recent years, but such systems have limited spatial resolution, making them less ideal for future applications requiring more precise stimulation or recording. Penetrating neural electrode arrays offer significantly improved temporal and spatial resolution but suffer from multiple complications which restrict their clinical use. A major complication is the limited ability to precisely position the electrode array's penetrating members, or shanks, in the desired location, which is exacerbated by tissue compression, particularly when the electrode array consists of multiple closely spaced penetrating members, as in the “bed of nails” designs of the Utah (Blackrock) or microwire electrode arrays. The mechanical stress of implantation may also lead to penetrating member damage or bending and deflection that further exacerbates the tendency to miss the desired target or fail to penetrate the tissue altogether.
Additionally, the trauma of implantation, including the dimpling of local tissue and nerves, may decrease recording yield and can cause and/or accelerate glial scarring which isolates the implant from the target tissue. Chronically placed neural penetrating members cause a reactive tissue response involving astrocytes and microglia that result in the formation of a cellular sheath or scar around the penetrating member. The response is highly complex with multiple chemical signaling pathways, cell types, and damage involved, but overall involves an initial acute phase of glial scarring in response to the initial injury followed by chronic inflammation. Previous studies comparing fast and slow insertion speeds have found that both electrophysiological and histological outcomes are more favorable with faster insertion so the faster insertion is often the approach typically used. Studies exploring the role of the electrode array density are largely lacking in the literature. However, given the fact that gliosis can often extend 500-600 μm beyond the implant-tissue interface, it is likely that there is compounding interaction among penetrating members that have overlapping regions of influence. In addition, more densely packed penetrating members will likely increase the implantation trauma and dimpling.
As a subset of neural implants—penetrating intracortical microelectrode arrays—are composed of multiple penetrating members with typical cross-sectional diameters in the range of 25-100 μm and are typically implanted 0.25-2 mm into brain tissue, but sometimes as deep as several centimeters when targeting deep brain structures in some animal species. The recording sites are relatively small with high impedance (>100 kΩ), a requirement for recording unit activity from individual neurons. Variations in penetrating electrode technologies include insulated metallic microwires, micromachined high density 3-D electrode arrays such as Utah electrode array that are similar in geometry to microwire electrode arrays, and planar thin-film microelectrode arrays like Michigan probes, also known as NeuroNexus, composed of silicon or polymer substrates with multiple electrode sites along the penetrating members. In addition to material and method of fabrication considerations, penetrating electrode designs may differ in: (a) geometry, including but not limited to tip shape, size and spacing of the penetrating members: (b) attachment state relative to the neural target, such as fixed or floating; and (c) insertion strategy, including by hand, manually with a micromanipulator, pneumatic impact, or mechanized insertion at fast or slow speeds. As the density of penetrating members of the electrode array increases, it is more likely to dimple or compress the neural tissue during implantation. One strategy employed for implantation of Utah electrode arrays in brain and nerve tissue is to use a pneumatic, single-shot, high speed impact inserter to essentially hammer the implant into neural tissue at high velocity in order to reduce dimpling. Since the inserter only makes momentary contact with the electrode array, this single shot approach does not allow for fine adjustment or correction if the initial placement is not ideal, or when fine anatomic details vary across subjects. Successful insertion is still often heavily reliant on surgical skill and technique.
Most types of neural microelectrode arrays, including microwires, 3-D silicon, and 2-D planar silicon devices, have published examples demonstrating the ability to record neural activity upwards of a year or more in many different subjects. However, the consistency in performance of penetrating neural microelectrode arrays is highly variable. For instance, a group at University of Michigan now has a team of individuals experienced in implanting their microelectrode arrays in subjects, and approximately 67% of the time the implants record unit activity for 3-6 months or more. However, the remaining 33% of the electrode arrays often fail at around 6 weeks, suggesting that if the microelectrode arrays can make it beyond this critical window, they could record neural activity indefinitely. According to an informal survey by Schwartz, any given recording electrode site on a penetrating member may only have a 40-60% chance of recording chronic neural activity and essentially all conductive penetrating members do eventually fail.
Therefore, a way to insert penetrating electrodes into neural tissue in a manner that preserves the integrity of the electrodes and minimizes damage and trauma to the surrounding neural tissue is still needed, for increased accuracy of placement and long-term use of the resulting embedded electrodes.
Peripheral neural targets like the dorsal root ganglia, nerves, spine, and even muscle tissue in the arms and legs present and even greater challenge for penetrating neural implant placement than that encountered for relatively soft tissue in the cortex of the brain. Compared to the brain, penetrating microelectrode array technology has been largely under-utilized in both basic and applied peripheral nervous system research. There are numerous reasons for this including greater difficulty in accessing and stabilizing the neural targets during surgery and challenges associated with either dissecting, or getting the shanks to penetrate, the neural membranes (epineurium or dura). There is increasing interest however in achieving direct interfacing with neural tissues outside the brain and with an approach that reduces tissue damage and improves implant location accuracy, allowing placement for instance in or near specific fascicles or neural circuits. As an example, the urinary system is a target for placement of penetrating neural implants where a great clinical need exists. Neurogenic bladder dysfunction, or the interruption in neural communication between the control circuit and bladder muscles, occurs in a staggering 70-84% of spinal cord injury patients. After spinal cord injury, lower urinary tract dysfunction generally presents as a reflexive bladder and sphincter paralysis. This is of particular concern in the military veteran population, where an estimated 32,000 spinal cord injury veterans suffer from micturition disorders. Inadequate post-injury management of lower urinary tract dysfunction can lead to complications from infection to total renal failure, which was previously the leading cause of death after spinal cord injury.
The ability to store and eliminate urine is regulated by a dynamic neural circuit integrating information from brain, spinal cord and peripheral autonomic ganglia. The lower urinary tract coordinates activity between smooth and striated muscles in the bladder and urethral outlet, to both store urine and void it. Numerous interventions attempt to treat neurogenic bladder dysfunction: timed voiding, manual expression, medications, catheterization (both intermittent and indwelling), and surgical procedures. The current clinical standard of care for neurogenic bladder dysfunction patients remains catheterization, however all forms of catheterization are associated with risk of infection, which causes these patients an average of 16 office and 0.5 emergency room visits per year and possible hospitalization. Alternative treatments to restore function of the neurogenic bladder system have been developed with varying degrees of success. in addition to catheterization, mechanical solutions such as artificial urethral sphincters, stents, and pumps have been tested, however all have similar risks of infection and limited functional lifespans. Pharmacology treatments like anticholinergic medications can also be used to relax the hyper-reflexive bladder but have systemic side effects like dry mouth and blurred vision.
Electrical control of the bladder through neuroprosthetics would avoid the inconvenience, recurring cost, and associated infection risk of catheterization, as well as the systemic problems from pharmacological drug herapies. The effectiveness of electrical stimulation devices is limited by a number of factors including the stimulation target, the type of stimulating electrode, surgical access to nerves, and device longevity. However, the effectiveness of existing electrical stimulation devices is restricted by limited surgical access to the nerves, difficulty in electrode placement, and poor stimulation specificity. Initial attempts at a nerve-based bladder control device relied on non-penetrating electrode technologies such as nerve cuffs that excite a large portion of the pudendal nerve, but this approach requires spatially segregated stimulation to avoid simultaneous activation of antagonistic muscle groups of the bladder. Penetrating multichannel electrodes allow more spatially specific activation of nerve fibers that could significantly improve outcomes. However, implantation of penetrating electrodes into nerves remains a great challenge. Piercing the epineurium requires the electrode to withstand forces which may buckle or break the electrode. In addition, nerves typically compress (dimple), stretch, and/or roll, which prohibits effective electrode insertion, increases risk of trauma, bleeding and inflammation to the nerve tissue, and may accentuate the chronic foreign body response (FBR) leading to cell death, peripheral nerve scaring, and device failure. For clinically viable chronic penetrating nerve interfaces, the insertion forces must be substantially reduced and the nerve must be better stabilized during electrode insertion process in a way that is both minimally invasive and temporary.
Multiple stimulation targets have been examined as potential sites for restoration of urinary function, with varying success. These include electrical stimulation of the bladder, transcutaneous electrical stimulation of various nerves, stimulation of sacral roots and nerves, stimulation of the spinal cord, and stimulation of peripheral nerves. The latter two approaches require highly invasive surgical procedures and have failure rates as high as 40%. For instance, stimulation of the pudendal nerve with a surface linear electrode, laparoscopically placed in soft tissue adjacent to the nerve has been performed. This procedure successfully controlled micturition in patients with overactive bladder but the low-resolution stimulation of the entire pudendal nerve bundle was insufficient for treatment of other types of bladder dysfunction. The pudendal nerve is a particularly good target for human bladder control, having consistent fascicular anatomy between individuals. An alternative extraneural electrode device, called BION, has shown some success, though technical failures and migration of the electrodes once embedded prohibited reliability. To improve stimulation specificity and more stable interface for longevity of the electrical stimulation effectiveness, an intraneural penetrating electrode solution is necessary. A promising approach with potential for future clinical use would involve peripheral nerve stimulation, but only with improved surgical approach and utilizing penetrating electrode arrays.
Intraneural, or penetrating microelectrodes are placed directly in the peripheral nerve and solve several problems presented by cuff and other extraneurally placed electrodes for interfacing with peripheral neural targets. Penetrating microelectrodes can be longitudinally implanted or transversely implanted, offering different surgical implantation strategies. Penetrating microelectrodes grant specificity of stimulation, as individual electrode surfaces and combinatorial activation of electrode pairs can target independent fascicles. Peripheral nerves also have considerable freedom of movement as compared to brain or spinal cord, so penetrating electrodes can also be more resistant to migration, as they are embedded in the nerve and more likely to move with the nerve as it may move in the body when surrounding tissues are stretched.
Without a means of stabilization during the insertion of penetrating neural implants, the nerves can stretch and roll which may prevent complete penetration or result in inaccurate placement of the implant. Furthermore, it is important for the orientation and trajectory of the penetrating members of the neural implant to remain parallel to the insertion axis and for the axis to remain constant relative to the neural target to prevent inaccuracy as well as to minimize the extent of damage to neural tissue adjacent to insertion tract. For peripheral neural targets, which are not as confined relative to rigid bone as the brain is, the insertion of penetrating neural implants is not straightforward and not readily available in the marketplace.
Another critical aspect for insertion of penetrating neural implants, whether for the central or peripheral nervous system, is the ability to securely grasp a wide range of implant shapes and styles. The implants, which are very small, often sub-millimeter dimensions on each side, need be firmly grasped so they do not move out of alignment with the insertion axis as they experience forces during penetration process. At the same time, the devices are often very fragile and extremely expensive to manufacture, so the means of grasping them needs to be gentle and not apply excessive mechanical forces that may crush, bend, or otherwise break the implant. Furthermore, the implant also needs to be easily released when it is positioned in the desired location in the tissue, without having to twist, turn, or apply excessive torque to the implant that may apply forces to the surrounding tissue or inadvertently move the implant out of the desired position.
A major contribution to the failure of electrodes over time is believed to be the stiffness mismatch between the tissue target and the neural implant, which can induce a damaging tissue response exacerbated by relative motion between the neural implant and surrounding neural tissue. Thinner, more flexible implants are therefore desirable but will be much more difficult to insert through tough peripheral neural targets. The challenge of inserting any penetrating microelectrodes, particularly flexible ones, is overcoming the penetration force of the tough epineurium layer around peripheral nerves, or the meningeal membranes of brain and spinal cord.
There is still much room for improvement in the field of electrode use for neurological stimulation, particularly in the areas of penetrating electrodes, floating arrays that are not anchored to bone, and in-dwelling or embedded implants that remain resident in the tissue for extended periods of time.
An electrode placement system is disclosed for the accurate and precise insertion and placement of penetrating electrodes into neural tissue, such as any tissues of the nervous system, including but not limited to the brain(including the cortical brain as well as deeper brain structures), spinal cord, dorsal root ganglion, peripheral nerves and peripheral nerve bundles. The system provides enhanced placement accuracy and functionality of penetrating nerve electrodes by stabilizing the neural target while vibrating the penetrating electrode during insertion, reducing insertion force and increasing insertion success while reducing strain and trauma to the neural tissue. As a result, this system improves implant location accuracy, allowing placement in and near specific cortical targets and/or nerve fascicles for highly specific electrode placement, neural stimulation and recording of neural activity.
The system of the present invention can be for the insertion and placement of any type of penetrating electrode, including stimulating and recording electrodes. The penetrating electrodes may be part of an implant or array, which can include a single or multiple penetrating members. The implants may be made of many different types of biocompatible materials, including but not limited to microwire, silicon, carbon fiber, optical fiber, and/or polymers and various composites The system can also be used to facilitate the insertion of thinner and more flexible implants and electrodes than current insertion options allow for. The current invention reduces the insertion force, implant buckling and breaking, and tissue dimpling to allow improved neural interface establishment. Furthermore, reducing the insertion force facilitates the insertion of thinner and more flexible penetrating electrodes because the buckling force requirements are reduced. Longer electrodes and probes can be more successfully inserted to a target location due to reduced buckling and deflection.
The system of the present invention may be hand-held in some embodiments, tabletop mounted such as on a stereotaxic frame in other embodiments and may be deployable through a trocar or laparoscope for clinical use and minimally invasive procedures in some embodiments.
The electrode placement system of the present invention includes a vibrational actuator configured to generate and deliver micro-vibrations to an implant having one or more penetrating members or shanks. The vibrations are provided axially along the insertion axis of the implant to oscillate the implant axially during insertion of the penetrating member(s) into target neural tissue. A translational motor is also included in the system to move the implant linearly along the insertion axis, to advance the penetrating electrode(s) along a desired path at a controlled speed into the target neural tissue and to release and retract the supporting components of the system once the implant is embedded in the target neural tissue. The system also includes a control unit with a processor and vibrational and translational drivers. The vibrational actuator and translational motor are each in electrical communication with the control unit and receive operative instructions from the respective drivers to activate and operate.
The system may also include a target stabilization assembly that is configured to contact and hold the target neural tissue in place during the insertion process, The target stabilization assembly provides mechanical stability of the target neural tissue and establishes a point of reference from which the system inserts the neural implant to the location of the desired neural target. It also limits the movement and stretch of the target neural tissue with minimal dissection The target stabilization assembly includes at least one arm having at least one finger at a terminal end. The arm(s) and finger(s) may be manipulated to engage the target neural tissue, either directly or through other anatomical structures such as the skull, such as an ear canal, and hold it in position for electrode insertion. In at least one embodiment, the arm(s) and finger(s) are selectively movable relative to one another, such as in the longitudinal direction parallel to the insertion axis of the implant, to grip a portion of the target neural tissue therebetween. The target stabilization assembly may also apply slight pressure to the target neural tissue, such as by pulling, pressing or vacuum, to increase the tautness of the surface of the target neural tissue and further limit movement of the target site.
The electrode placement system also includes an insertion assembly configured to selectively retain and release the implant having at least one penetrating member. The insertion assembly includes a horn that is connected to or part of the vibrational actuator and transmits the axially-directed vibrations to the implant and electrode(s) during insertion. The horn tip located opposite from the vibrational actuator is shaped to contact and abut the implant, and may have a recess formed therein in certain embodiments correspondingly shaped to receive a portion of the implant therein for increased stabilization, The insertion assembly also includes an implant stabilizer of stiff yet bendable material that is displaceably mounted to the horn at a connection point. A first end of the implant stabilizer extending from the connection point is positioned proximate to the horn tip and is configured to contact and hold the implant against the horn tip in tight enough contact for effective vibration transfer. A second end of the implant stabilizer extends from the opposite side of the connection point and is selectively movable under the application of force, causing the first end to also move relative to the horn tip. A biasing member contacts the first end of the implant stabilizer and the horn tip and urges the first end of the implant stabilizer d the horn tip to provide force on the implant for retention and vibrational energy coupling to the implant. Application of force to the second end of the implant stabilizer moves the first end in a direction away from the horn tip, limited by the biasing member but sufficient enough to release the grip on the implant for loading or release of the implant. The biasing member may also be selectively removed from the insertion assembly, such as by cutting, when the penetrating electrode(s) of the implant are inserted to the desired target without perturbing the electrode(s) so the insertion assembly may be removed, leaving the implant embedded in place in the target site.
The electrode placement system, together with its particular features and advantages, will become more apparent from the following detailed description and with reference to the appended drawings.
Like reference numerals refer to like parts throughout the several views of the drawings.
As shown in the accompanying drawings, the present invention is directed to an electrode placement system 100 for the precision insertion and embedding of electrodes into neural tissue 5. The system 100 can be used to insert one or more electrode penetrating members 122, either singly or in a combined implant 121, into a desired neural target. As used herein, the term “implant” may refer to a penetrating electrode array, which is inserted and anchored in the neural tissue 5, bringing the electrode sites closer to the underlying neurons while restricting the migration of the implant relative to the neural tissue as might occur with a non-penetrating extra-neural implant. Penetrating electrode arrays therefore allow specificity of stimulation, as individual electrode surfaces can target independent fascicles and/or neural circuits. Activation of opposing functions may be avoided if appropriate populations of nerve fibers within individual fascicles, or specific neurons of a circuit or center, can be selectively targeted. The neural tissue targeted for insertion and electrode implantation may be any neural target, including but not limited to brain tissue (including cortical and/or deep brain structures), the spinal cord, and peripheral nerves. The system 100 utilizes oscillation vibrations in the ultrasonic frequency range to reduce the force required for insertion and implantation of electrode arrays and to reduce the dimpling of the soft tissue that is being penetrated. The objective of the system 100 is to improve insertion success while reducing strain and trauma to recipient tissue.
The electrode placement system 100 includes a vibrational actuator 110, an insertion assembly 120, a control unit 130, a translational motor 140 and a target stabilization assembly 150, as depicted in
A major contribution to the failure of electrodes over time is believed to be the mismatch in stiffness between the target tissue and the neural implant. For example, a stiff or rigid penetrating member 122 can injure the surrounding softer tissue as a result of mechanical motion, which can in turn induce a damaging tissue response. Flexible and/or ultra-fine implants, such as 7-8 μm diameter carbon fibers, are therefore desirable but are much more difficult to insert through tough tissues, such as peripheral nerve targets. The challenge of inserting electrode penetrating member(s) 122, particularly a flexible ones, is to ensure the force required to penetrate the tough epineurium layer in the peripheral nervous system remains below the buckling force of the implanted penetrating member(s) 122 of the neural implant 121.
The present system 100 includes a vibrational actuator 110, depicted in
The vibrational actuator 110 may be any motor capable of generating vibrations, preferably axial vibrations. For instance, in at least one embodiment the vibrational actuator 110 may be a piezoelectric stack actuator with 25 kHz resonant frequency. In other embodiments, the vibrational actuator 110 may be a voice-coil motor capable of generating vibrations at a lower frequency, such as in the range of about 100-200 Hz, and higher displacements (also referred to as amplitudes) such as up to hundreds of microns. In other embodiments of the system 100, such as may be used in laparoscopic and other applications, the vibrational actuator 110 may be capable of generating vibrations with amplitudes in the range of 0.05 to 0.5 mm and at frequencies in the range of about 80-200 Hz.
The electrode placement system 100 also includes a translational motor 140 interconnected to the implant 121 and capable of moving the implant 121 in a linear fashion into the target neural tissue 5. The translational motor 140 may be any suitable motor, such as but not limited to a linear motor, screw driven motor, conveyor belt, track-based motor, rack and pinion motor, rotational motor, hydraulic motor and others. The translational motor 140 may be configured to advance the implant 121 at suitable velocities, such as in the range of about 0.1 μm/s to 5 mm/s in some embodiments, more preferably in the range of about 0.5 μm/s to 1 mm/s. In at least one embodiment the translational motor 140 may be operated at a speed of about 50 μm/sec. The speed of operation of the translational motor 140 may be set or variable and may be determined by the power supplied to it, such as up to 5 watts in at least one embodiment. The translational motor140 may provide insertion displacements in the range of about 100 μm to 20 cm, and preferably in the range of 100 μm to 10 cm in at least one embodiment.
The electrode placement system 100 also includes a control unit 130, as shown in
In some embodiments, the electrode placement system 100 may also include a visualization aid 159, as shown in
The electrode placement system 100 also includes a target stabilization assembly 150, as depicted in
The frame 151 may also include a first arm 152 and opposite second arm 154 each mounted to the frame 151 and each terminating in a finger 156, 158, respectively. The arms 152, 154 are selectively moveable in the frame 151 relative to one another to increase and decrease the distance between the respective fingers 156, 158. In at least one embodiment, the arms 152, 154 are selectively movable in a linear direction toward and away from one another. This linear direction may be transverse or orthogonal to the insertion axis 128 of the implant 121 for insertion. The fingers 156, 158 are configured to contact and hold the neural tissue 5 in position, as shown in
In some embodiment, the target stabilization assembly 150 may be sufficiently elongate, narrow and flexible to be inserted through a channel of a laparoscope. In such embodiments, target stabilization assembly 150 and insertion assembly 120 discussed below must be able to work at some considerable distance from the operator, possibly after passing through a trocar, and occasionally under significant curvature before reaching the nerve target. Therefore, in such embodiments, the target stabilization assembly 150, insertion assembly 120 and implant 121 may be compatible in size with minimally invasive surgical approach, such as through a 5 mm laparoscopic port or trocar, and where the target neural tissue may be at a distance of about 10 cm and have a diameter of less than 4 mm.
The target stabilization assembly 150, insertion assembly 120 and implant 121 may therefore be included or housed in a delivery stem having an inner core and surrounding outer sheath. The inner core may be a guide wire or other similar elongate structure that is sufficiently flexible to pass through the curvature necessary for a laparoscopic approach but also rigid enough to provide structural support and transmit vibrations from the vibrational actuator 110 located outside of the laparoscope to the implant 121 at the distal end of the inner core. Accordingly, the inner core may be the insertion assembly 120 in laparoscopic embodiments. The outer sheath may be a semi-flexible, low friction material such as Teflon or nylon that surrounds the inner core and enables the delivery stern to be gripped from the outside without significantly damping the oscillation of the inner core. The outer sheath may be retracted for insertion of implant. An endoscopic-style manipulator may also be inserted with flexibility, but then made rigid with a cabling system. A visualization aid 159, such as a camera and/or light, may also be inserted through a channel of the laparoscope.
In some applications, such as penetration of peripheral targets like dorsal root ganglion (DRG) and peripheral nerves, insertion is more challenging because the targets are tougher and have increased freedom of movement. In addition, for the peripheral nervous system, anatomy is often more variable between subjects and stereotaxic approaches are far less useful and common. Therefore, surgical approaches for electrode placement may be more reliant on manual, handheld equipment as there is often not a good way to mount hardware or fixturing.
Accordingly, in certain embodiments of the electrode insertion system 100, the target stabilization assembly 150′ may be handheld, as shown in
In this embodiment, the target stabilization assembly 150′ includes at least one arm 152′, and preferably includes a first arm 152′ and second arm 154′ each having an elongate length extending from the housing 151′ parallel to the insertion axis 128 for the electrode penetrating member(s) 122 and/or implant 121. Each arm 152′, 154′ includes at least one finger 156′, 158′, respectively, and preferably has more than one finger 156′, 158′. In at least one embodiment, as shown in
Each arm 152′, 154′ is also selectively moveable relative to one another and relative to target neural tissue 5 to grasp and secure the target neural tissue 5 in a fixed or stationary position relative to the electrode penetrating member 122 and/or implant 121 for more precise insertion. Not only is the target stabilization assembly 150′ handheld and moveable in space by the user, the first and second arms 152′, 154′ are also selectively moveable in a longitudinal axis that is parallel to the insertion axis 128 of the insertion assembly 120. For instance, as shown in
The target stabilization assembly 150′ also includes at least one locking mechanism 153′, as shown in
In some embodiments, each arm 152′, 154′ may be affixed and slidable along its own track. The locking mechanism 153′, 155′ may extend through arm 152′, 154′ and may be tightened down onto the track when the appropriate location along the track is achieved, In some instances, the locking mechanism 153′, 155′ may be affixed to the respective arm152′, 154′ and the portion of the locking mechanism 153′, 155′ that extends through the housing 151′ may be used as a handle to move the arm 152′, 154′, such as by sliding, in the longitudinal direction to adjust the position and achieve the desired location, then may be turned to secure the arm 152′, 154′ in place. In such embodiments, the housing 151′ may include an aperture through which a portion of the locking mechanism 153′, 155′ may extend and may be movable within. In such embodiments, the aperture of the housing 151′ may therefore limit the degree of movement of the arms 152′, 154′.
In action, at least one of the arms 152′, 154′ may be extended from the housing 151′ in a longitudinal direction until the fingers 156′, 158′ are positioned on either side of a target neural tissue 5, as shown in
In still further embodiments, the target stabilization assembly 150 may utilize vacuum to hold the target neural tissue 5 in position. For instance, as shown in
In still further embodiments, as shown in
In a still further embodiment, as shown in
Keeping the implant 121 stabilized during insertion is important for accuracy and precision of placement at the desired target site. This is true, and can be challenging, when the implant 121 is a single electrode penetrating member 122 but is particularly challenging for implants 121 having multiple electrode penetrating members122, such as floating arrays which are not fixed to bone once implanted and may therefore designed to “float” or move freely with the neural tissue, and for microelectrodes having an extremely small scale requiring heightened precision. The need for implant 121 stabilization is even more important in view of the vibrations that are transmitted to the implant 121 during insertion from the vibrational actuator 110. Indeed, floating arrays typically have a highly flexible cable of wires, called a tether or cable 125, connected to a base 124 of the implant 121, as depicted in
To overcome this, the electrode placement system 100 of the present invention includes an insertion assembly 120 configured to secure the implant 121 during vibration and insertion, and then selectively release the implant 121 once inserted into the desired target site without perturbing the final placement of the implant 121 in the insertion site. As shown in
The horn tip 117 is dimensioned to abut at least a portion of the implant 121 therein, such as the base 124 of an implant 121 as shown in
The horn tip 117 is configured to support a portion of the base 124 of the implant 121. For instance, in some embodiments the base 124 of the implant 121 may be held against the horn tip 117 by the implant stabilizer 170, described below in greater detail. In at least one embodiment as shown in
The insertion assembly 120 also includes an implant stabilizer 170 configured to securely hold the implant 121 against the horn 115 with a sufficient force to allow the transmission of vibrations from the vibrational actuator 110 through the implant 121 to the penetrating members 122 during insertion, but also is selectively releasable from the implant 121 without perturbing the placement or position of the implant 121 once inserted. The implant stabilizer 170 includes a first end 174 positioned proximate to the horn tip 117, and therefore implant 121. The first end 174 of the implant stabilizer 170 is capable of selectively contacting a portion of the implant 121, such as the base 124, to hold the implant 121 in place against the horn tip 117. The point of contact between the first end 174 and the implant 121 should be as close to the penetrating members 122 as possible without interfering with them or the vibration transmitted to them, to provide the most control over the implant 121 during insertion. In at least one embodiment, the first end 174 may have a solid construction, as shown in
The implant stabilizer 170 also includes a second end 172. opposite from the first end 174. In at least one embodiment, the second end 172 and first end 174 of the implant stabilizer 170 may be of a unitary construction, though in certain embodiments they may be separate pieces joined together. The implant stabilizer 170 is displaceably mounted to the horn 115 such that it is secured to the horn 115 at a connection point 176 and yet is also bendable about the connection point 176 upon the application of force. Each of the second end 172 and first end 174 may have an elongate length to enable torque to be provided through the connection point 176. The implant stabilizer 170 may be made of material such as acetal, though it may be made of any stiff yet bendable or resilient material such as plastics, polymers, polymer blends, rubber, and other natural or synthetic materials such as having a hardness of greater than 60A Shore, though more optimally greater than 70D Shore. The second end 172 may extend away from the connection point 176 in the direction of the horn base 116. In at least one embodiment, the second end 172 may extend at an angle relative to the insertion axis 128 such that it deviates from the axis. The first end 174 may also extend at an angle relative to the insertion axis 128, which may be the same or different angle relative to the insertion axis 128 as that of the second end 172. In at least one embodiment the angle the first end 174 deviates from the insertion axis 128 is less than that of the second end 172. The angles of the first and second ends 174, 172 relative to the insertion axis 128 may be any angle up to 140 degrees. For instance, in at least one embodiment the first end 174 is positionable at an included angle in the range of 10-60 degrees relative to the insertion axis 128, depending on whether force is applied or not. Similarly, the second end 172 may be positionable at an included angle in the range of 25-90 degrees relative to the insertion axis 128, depending on whether force is applied or not.
The second end 172 may also have a tab 173 that protrudes from the second end 172. The tab 173 may extend or protrude from any location along the second end 172, such as at a terminal end, or along the length of the second end 172 such as a fin and may have any shape or configuration. In at least one embodiment, the tab 173 may have a generally square or rectangular shape, as shown in
The implant stabilizer 170 secures to the horn 115 at the connection point 176, which may be at any location along the length of the horn 115 such as along the insertion axis 128 in some embodiments and off-axis from the insertion axis 128 in other embodiments. In at least one embodiment the connection point 176 attaches the implant stabilizer 170 to the horn 115 at a position that aligns the terminal end of the first end 174 with terminal end of the horn tip 117, such as with the recess 118 formed therein. This positioning allows the maximum torque to be applied by the first end 174 on the implant 121 when held in place. However, in other embodiments the connection point 176 may attach lower on the horn 115, closer to the horn tip 117, which may provide increased control of the implant 121 or may allow the first end 174 to extend beyond the base 124 of the implant 121 when holding the base 124 of the implant 121 and/or the horn tip 117. The connection point 176 may include hardware for connection, such as a screw, nut, bolt, washer, bearing and combinations thereof, and may include welding or adhesive in certain embodiments. Regardless of the material used for the connection point 176, it is preferably made of a material that is sufficiently light that it does not dampen or otherwise interfere with the vibrations from the vibrational actuator 110. Examples may include, but are not limited to, stainless steel, nylon, or polyether ether ketone (PEEK).
The implant stabilizer 170 has a construction and is of a material that permits movement of the second end 172 about the connection point 176 when force is applied to the second end 172. Specifically, force may be applied to the second end 172 in the direction of arrow 179, shown in
In at least one embodiment, the insertion assembly 120 also includes a biasing member 178 contacting the first end 174 and providing a biasing force such as torque against the first end 174 to hold the first end 174 against the horn 115, and therefore against the implant 121. As shown in the embodiment of
Once the implant 121 is fully seated, the force on the second end 172 is relieved and the second end 172 rotates back to its natural position, as shown in
Once the electrode penetrating member(s) 122 of the implant 121 are embedded in the target site of the neural tissue 5, the implant stabilizer 170 may be removed from contact with the implant 121 by again applying force to the second end 172, or by selectively releasing the biasing member 178 from the insertion assembly 120, as shown in
Once the biasing member 178 is released and the first end 174 is no longer holding the implant 121, the insertion assembly 120 and rest of the system 100 may be removed from the insertion site, leaving the implant 121 embedded in the neural tissue 5, as shown in
In other embodiments, the implant stabilizer 170 may be a clamp mechanism where the first end 174 is a base and the second end 172 is a top that may be secured to the base such as with screws, such as shown in
In still other embodiments, the implant stabilizer 170 may be a cam positioned adjacent to the implant 121 and having a cam profile that contacts and provides adequate force to the implant 121 when the cam is rotated to allow effective vibrational energy transfer from the actuator 110 to the implant 121 while at the same time not overloading the implant 121 to the point of damaging the electrode penetrating member(s) 122.
In still further embodiments, the implant stabilizer 170 may be polyethylene glycol (PEG) that is potted around the implant 121, such as the base 124 and possibly even portions of the electrode penetrating member(s) 122, to provide structural stability during insertion while also permitting transmission of vibrational energy from the actuator 110 to the electrode penetrating member(s) 122. Once the implant 121 is inserted and embedded in the target neural tissue 5, the PEG may be dissolved by the application of an aqueous solution such as saline, and/or by heating a small wire integrated into the implant 121, such as the base 124 of the implant 121, to facilitate the melting of the PEG following implantation.
Since many modifications, variations and changes in detail can be made to the described preferred embodiments, it is intended that all matters in the foregoing description and shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents. Now that the invention has been described.
The present application claims priority to U.S. Provisional Application Ser. No. 62/851,235 filed on May 22, 2019, the contents of which are incorporated herein by reference in its entirety.
This invention was made with government support under HR0011-16-C-0094 awarded by the Defense Advanced Research Projects Agency; under NS105500 awarded by the National Institutes of Health/National Institute of Neurological Disorders and Stroke; and under DK120349 awarded by the National Institutes of Health/National Institute of Diabetes and Digestive and Kidney Diseases. The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 62851235 | May 2019 | US |
