Stimulation lead for application of electrical pulses to tissue of a patient and method for fabricating a stimulation lead

A method of fabricating a stimulation lead by supplying a lead body with a plurality wire conductors extending the length of the lead body and being within insulative material therein; providing a plurality of terminals and electrodes on the ends of the lead body, wherein the plurality of terminals and electrodes are electrically coupled, wherein the providing comprises: (i) positioning a conductive band about the lead body that is adapted to be clasped about the lead body; (ii) positioning a conductor wire between an exterior surface of the first end and an interior surface of the second end of the conductive band; (iii) closing overlapping ends of the conductive band about the conductor wire; and (iv) welding the ends to seal the conductive band about the lead body.

TECHNICAL HELD

This application is generally related to a stimulation lead for application of electrical pulses to tissue of a patient and method for fabricating a stimulation lead.

BACKGROUND

Neurostimulation systems are devices that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is the most common type of neurostimulation. In SCS, electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control. Applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions which can effectively mask the transmission of non-acute pain sensations to the brain.

Neurostimulation systems generally include a pulse generator and one or more leads. The pulse generator is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generating circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator.

Each stimulation lead includes a lead body of insulative material that encloses wire conductors. The distal end of the stimulation lead includes multiple electrodes that are electrically coupled to the wire conductors. The proximal end of the lead body includes multiple terminals, which are also electrically coupled to the wire conductors, that are adapted to receive electrical pulses. The distal end of a respective stimulation lead is implanted at the location adjacent or within the tissue to be electrically stimulated. The proximal end of the stimulation lead is connected to the header to the pulse generator or to an intermediate “extension” lead.

The manufacture of stimulation leads is a relatively complex process. Some manufacturing techniques involve wrapping conductor wires with insulative coatings about a mandrel in a helical manner to form a lead body. An example of a system adapted to perform such winding is shown in U.S. Pat. No. 7,287,366, entitled “Method for producing a multielectrode lead,” which is incorporated herein by reference. Upon fabrication of a lead body electrodes and terminals are provided to the lead body. A variety of techniques exist for electrode and terminal fabrication. Some known techniques involve employing a “blind weld” to electrically couple a respective electrode to a wire of the lead body.

SUMMARY

In one embodiment, a method of fabricating a stimulation lead for applying electrical pulses to tissue of a patient, comprises: supplying a lead body, wherein the lead body comprises a plurality of wire conductors extending from a proximal end of the lead body to a distal end of the lead body, and the plurality of conductor wires are disposed within insulative material of the lead body; and providing a plurality of terminals and electrodes on the proximal end and the distal end of the lead body respectively, wherein the plurality of terminals and electrodes are electrically coupled through the plurality of wire conductors; wherein the providing comprises: (i) positioning a conductive band about the lead body, wherein the conductive band comprises a first end and a second end and the first end and second end are adapted to be clasped together; (ii) positioning a conductor wire between an exterior surface of the first end and an interior surface of second end of the conductive band; (iii) closing the first end and second end of the conductive band about the conductor wire wherein the first end and second end are disposed in an overlapping arrangement; and (iv) welding the first end and second end to seal the conductive band about the lead body.

The foregoing has outlined rather broadly certain features and/or technical advantages in order that the detailed description that follows may be better understood. Additional features and/or advantages will be described hereinafter which form the subject of the claims. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the appended claims. The novel features, both as to organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the appended claims.

DETAILED DESCRIPTION

In one embodiment, a process for fabricating lead body material for stimulation leads begins with a continuous core material10shown inFIG. 1. In one embodiment, the core material10is a polytetrafluoroethylene (PTFE) coated stainless steel mandrel wire12(shown inFIG. 2), although additional insulative layers may also be provided according to other embodiments. Referring again toFIG. 1, the core material10is then helically wrapped with a set of insulated wires14at a wire wrapping system15. Systems for helically winding wires for fabrication of a lead body are disclosed in U.S. Provisional Application Ser. No. 61/247,264, entitled “System and method for fabricating a stimulation lead,” and U.S. Pat. No. 7,287,366, entitled “Method for producing a multi-electrode lead,” which are incorporated herein by reference.

Each of the wires14may include one or more layers of insulation. In one embodiment, each wire14comprises an inner thin layer of perfluoroalkoxy (PFA) and outer thicker layer of a thermoplastic silicone polycarbonate urethane (e.g., CARBOSIL™). While eight insulated wires are used in one embodiment, those skilled in the art will recognize that any suitable number of wires may be wrapped onto mandrel12according to other embodiments. In other embodiments, additional layers of wires14may be wound over the initial layer(s) of wires.

In one preferred embodiment, wires14are wrapped about core material10in an axially repeating pattern of groups301of closely spaced wires with each group301separated by distance302that is larger than the spacing between adjacent wires within each group (FIG. 3). The distance between groups inFIG. 3is by way of example and any suitable distance may be employed according to some embodiments.

Referring again toFIG. 1, core material10, now comprising mandrel12and helically wrapped insulated wires14may now be spooled and later unspooled (not shown) or fed directly to the next step in the process. In the next step, core material10may be selectively and repeatedly heated in a reflow oven18. The wires14are heated to a temperature that causes the insulation of insulated wires14to approach or achieve a phase change, thereby becoming soft and adherent and ultimately fusing together, by heating, melting and re-solidifying after removal from reflow oven18.

At this point, the core material10, now comprising mandrel12having insulated wires14at least partially fused about it, may now be spooled (step19) onto a spool and stored for later work. Alternatively, step19is not performed and core material10proceeds directly to the remaining steps. Continuous core material10is cut (step24) into individual lead bodies21. Each individual lead body21may have a length of from about 10 cm (4 in) to about 150 cm (60 in).

After the lead bodies21have been cut to length, mandrel12is removed in a mandrel removal step28. This task may be facilitated by a coating of mandrel12that will ease removal, such as a PTFE coating. The mandrel removal step28may be a simple hand operation by a human worker.

Next, in an electrode creation step30, electrodes are provided on the distal end of the lead body. In step32, terminals are provided on the proximal end of the lead body. Electrode and terminal fabrication are further discussed below.

FIG. 4depicts a cross-sectional view of lead body assembly400according to one representative embodiment. Lead body assembly400comprises stainless steel mandrel420which is coated with layer401of PTFE. Inner layer402of CARBOSIL™ is extruded or otherwise provided over the inner layer of PTFE. The mandrel420with layers401and402is utilized as core material10in wire wrapping system15. Each wire410(only one wire is annotated for the sake of clarity) is preferably stranded wire coated with a thin layer of PFA and a thicker layer of CARBOSIL™. Wire wrapping system15wraps a plurality of wires410about mandrel420, layer401, and layer402in the manner discussed above. An outer layer403of CARBOSIL™ is also provided. Shrink wrap tubing404is then provided on the exterior of the assembly.

Lead body400is cut to length and lead body assembly400is subjected to heating above the melting point of the thermoplastic material. The heat and pressure (e.g., from heat shrinkable tubing) causes the thermoplastic insulative material (e.g., the CARBOSIL™ material) to flow. After the thermoplastic material is cooled, the thermoplastic material re-solidifies into a lead body500of fused insulative material enclosing the respective conductors410. Also, as shown inFIG. 16, gap610is provided within lead body500where no conductors are located within gap610. That is, gap610is entirely filled with insulative material.

In one embodiment, the lead body is fabricated so that the lead body is capable of elastic elongation under relatively low stretching forces. Also, after removal of the stretching force, the lead body is capable of resuming its original length and profile. For example, in one embodiment, relatively low durometer, elastic polymer material is used for the material of the lead body. The combination of the selection of the materials, the helically wrapping of the wires, and the repeating groups of wires with separating gaps enables the stretching according to the relatively low stretching forces. For example, the lead body may stretch 10%, 20%, 25%, 35%, or even up to 50% at forces of about 0.5, 1.0, and/or 2.0 pounds of stretching force. For additional description of a lead body capable of elastic elongation, reference is made to U.S. Patent Publication No. 2007/0282411, entitled “COMPLIANT ELECTRICAL STIMULATION LEADS AND METHODS OF FABRICATION,” which is incorporated herein by reference. Although some specific lead body fabrication techniques are discussed herein, any suitable processes may be employed for lead fabrication. Alternative example lead fabrication processes are discussed in U.S. Pat. Nos. 5,555,618 and 6,216,045, which are incorporated herein by reference.

Lead body500is then cut into appropriate lengths and electrodes and terminals are provided.

FIG. 6depicts a cross-sectional view of conductive band600according to one representative embodiments. Conductive band600may be employed to provide the electrodes and/or terminals of a stimulation lead. Conductive band600may be fabricated using any suitable conductive material. In one specific embodiment, conductive band600is fabricated using a platinum iridium ahoy. Conductive ring is not a single continuously connected ring of material. Instead, band600comprises first end601and second end602. First end601and second end602are moveable. Conductive band600may be placed in an open position as shown inFIG. 6. Conductive bands600is also adapted to be placed in a dosed position as shown inFIG. 7with first end601and second end602disposed in an overlapping arrangement.

Referring toFIG. 6, conductive band600comprises opposing surface features603and604. Surface feature603is disposed on an “exterior” side of end601and surface feature604is disposed on an “interior” side of end602. Surface features603and604may be formed using suitable miffing or laser etching techniques. Surface features603and604are adapted to interconnect or mate with each other. In one embodiment, surface features603and604comprise a saw-tooth pattern. Also, in one embodiment, band600is implemented to possess a spring-characteristic which provides a biasing force to press surface features603and604against each other when band600is placed in the dosed position.

Surface features603and604optionally include sub-features605and606, respectively. Sub-features605and606are adapted to clamp about a conductive wire when band600is placed in the closed position.FIG. 7depicts conductive band600in the closed position. As shown inFIG. 7, conductive band600includes recess701(formed by sub-features605and606). Recess701is adapted to the size of a suitable conductive wire for electrical connection with conductive band600when conductive band600is integrated with the lead body.FIG. 8depicts an isometric view of conductive band600in the dosed position with conductive wire801crimped within recess701. After wire801is placed within conductive band600is this manner, laser or other suitable welding is preferably applied to permanently seal conductive band600.

FIG. 9depicts a process for providing an individual terminal or electrode on a lead body of a stimulation lead under fabrication. The process ofFIG. 9may be repeated for each of the electrodes and/or terminals to be provided on the end-product stimulation lead.

In901, insulative material is removed from the lead body to expose a conductor wire of lead body. The insulative material may be removed using any suitable technique. Manual operations may be employed. In another embodiment, a suitable laser may be employed to ablate insulative material from the lead body.

In902, a length of the exposed wire is freed from the lead body. Alternatively, a jumper wire may be attached to the exposed portion of the conductor wire of the lead body (see e.g., U.S. Pat. No. 6,952,616, entitled “Medical lead and method for electrode attachment,” which is incorporated herein by reference).

In903, conductive band600is provided about the lead body adjacent to the exposed wire of the lead body.

In904, the exposed wire or the jumper wire is placed within conductive band600. Conductive band600is then dosed about the wire (905) and around the lead body. In some embodiments, the wire is positioned within an interior aperture or recess701of conductive band600when the conductive band is dosed. Conductive band600is subjected to laser welding or other suitable welding to permanently seal the conductive band about the lead body (906).

It is believed that the electrode fabrication according to some embodiments may provide one or more advantageous. For example, a “blind” weld is not required for some embodiments. Also, the welding technique of some embodiments is less technique dependent and may result in greater manufacturing yields. Moreover, it is believed that the mechanical characteristics involved with the conductor wire and the conductive band for some embodiments may be more robust than other known attachment techniques. Also, since crimping is not necessarily employed, less scrap material may be used for some embodiments.

FIG. 10depicts percutaneous lead1000fabricated according to some embodiments. Lead1000comprises a plurality of electrodes and terminals fabricated using conductive bands600according to some representative embodiments. Although lead1000is shown to be fabricated as a “percutaneous lead,” other lead designs may also be employed such as paddle-style leads where only the terminals are fabricated using conductive bands600. Also, not all of the electrodes of a stimulation lead need involve the use of band600. For example, a conventional “tip” electrode design could be employed for the most distal electrode of lead1000if desired for a particular medical therapy. Further, although some embodiments have discussed fabrication of neurostimulation leads, other medical leads may be fabricated according to other embodiments, such as cardiac leads, mapping leads, ablation leads, etc.

FIG. 11depicts stimulation system1150that generates electrical pulses for application to tissue of a patient according to one embodiment. In one embodiment, system1150is adapted to generate electrical pulses and deliver the pulses to tissue of the patient. For example, system1150may be adapted to stimulation spinal cord tissue, peripheral nerve tissue, deep brain tissue, cortical tissue, cardiac tissue, digestive tissue, pelvic floor tissue, or any other suitable tissue within a patient's body.

System1150includes implantable pulse generator1100that is adapted to generate electrical pulses for application to tissue of a patient. Implantable pulse generator1100typically comprises a metallic housing that encloses pulse generating circuitry1102, controller1101, charging coil (not shown), battery1103, far-field and/or near field communication circuitry (not shown), battery charging circuitry1104, etc. of the device. Although an implantable pulse generator is shown for the embodiment ofFIG. 11, an external pulse generator (e.g., a “trial” stimulator) may alternatively be employed. The controller1101typically includes a microcontroller or other suitable processor for controlling the various other components of the device. Software code is typically stored in memory of the pulse generator1100for execution by the microcontroller or processor to control the various components of the device.

A processor and associated charge control circuitry for an implantable pulse generator is described in U.S. Patent Publication No. 20060259098, entitled “SYSTEMS AND METHODS FOR USE IN PULSE GENERATION,” which is incorporated herein by reference. Circuitry for recharging a rechargeable battery of an implantable pulse generator using inductive coupling and external charging circuits are described in U.S. patent Ser. No. 11/109,114, entitled “IMPLANTABLE DEVICE AND SYSTEM FOR WIRELESS COMMUNICATION,” which is incorporated herein by reference.

An example and discussion of “constant current” pulse generating circuitry is provided in U.S. Patent Publication No. 20060170486 entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONAL VOLTAGE CONVERTER AND METHOD OF USE,” which is incorporated herein by reference. One or multiple sets of such circuitry may be provided within pulse generator1100. Different pulses on different electrodes may be generated using a single set of pulse generating circuitry using consecutively generated pulses according to a “multi-stimset program” as is known in the art. Alternatively, multiple sets of such circuitry may be employed to provide pulse patterns that include simultaneously generated and delivered stimulation pulses through various electrodes of one or more stimulation leads as is also known in the art. Various sets of parameters may define the pulse characteristics and pulse timing for the pulses applied to various electrodes as is known in the art. Although constant current pulse generating circuitry is contemplated for some embodiments, any other suitable type of pulse generating circuitry may be employed such as constant voltage pulse generating circuitry.

Stimulation system1150further comprises one or more stimulation leads1120. Stimulation lead1120comprises a lead body of insulative material about a plurality of conductors that extend from a proximal end of lead1120to its distal end. The conductors electrically couple a plurality of electrodes600to a plurality of terminals (not shown) of lead1120. The terminals are adapted to receive electrical pulses and the electrodes600are adapted to apply stimulation pulses to tissue of the patient. Also, sensing of physiological signals may occur through electrodes600, the conductors, and the terminals. Additionally or alternatively, various sensors (not shown) may be located near the distal end of stimulation lead1120and electrically coupled to terminals through conductors within the lead body1111.

Stimulation system1150optionally comprises extension lead1110. Extension lead1110is adapted to connect between pulse generator1100and stimulation lead1120. That is, electrical pulses are generated by pulse generator1100and provided to extension lead1110via a plurality of terminals (not shown) on the proximal end of extension lead1110. The electrical pulses are conducted through conductors within lead body1111to housing1112. Housing1112includes a plurality of electrical connectors (e.g., “Bal-Seal” connectors) that are adapted to connect to the terminals of lead1120. Thereby, the pulses originating from pulse generator1100and conducted through the conductors of lead body1111are provided to stimulation lead1120. The pulses are then conducted through the conductors of lead1120and applied to tissue of a patient via electrodes600.

In practice, stimulation lead1120is implanted within a suitable location within a patient adjacent to tissue of a patient to treat the patient's particular disorder(s). The lead body extends away from the implant site and is, eventually, tunneled underneath the skin to a secondary location. Housing1112of extension lead1110is coupled to the terminals of lead1120at the secondary location and is implanted at that secondary location. Lead body1111of extension lead1110is tunneled to a third location for connection with pulse generator1100(which is implanted at the third location).

Controller device1160may be implemented to recharge battery1103of pulse generator1100(although a separate recharging device could alternatively be employed). A “wand”1165may be electrically connected to controller device through suitable electrical connectors (not shown). The electrical connectors are electrically connected to coil1166(the “primary” coil) at the distal end of wand1165through respective wires (not shown). Typically, coil1166is connected to the wires through capacitors (not shown). Also, in some embodiments, wand1165may comprise one or more temperature sensors for use during charging operations.

The patient then places the primary coil1166against the patient's body immediately above the secondary coil (not shown), i.e., the coil of the implantable medical device. Preferably, the primary coil1166and the secondary coil are aligned in a coaxial manner by the patient for efficiency of the coupling between the primary and secondary cons. Controller1160generates an AC-signal to drive current through coil1166of wand1165. Assuming that primary coil1166and secondary coil are suitably positioned relative to each other, the secondary coil is disposed within the field generated by the current driven through primary coil1166. Current is then induced in secondary coil. The current induced in the coil of the implantable pulse generator is rectified and regulated to recharge battery1103by charging circuitry1104. Charging circuitry1104may also communicate status messages to controller1160during charging operations using pulse-loading or any other suitable technique. For example, controller1160may communicate the coupling status, charging status, charge completion status, etc.

External controller device1160is also a device that permits the operations of pulse generator1100to be controlled by user after pulse generator1100is implanted within a patient, although in alternative embodiments separate devices are employed for charging and programming. Also, multiple controller devices may be provided for different types of users (e.g., the patient or a clinician). Controller device1160can be implemented by utilizing a suitable handheld processor-based system that possesses wireless communication capabilities. Software is typically stored in memory of controller device1160to control the various operations of controller device1160. Also, the wireless communication functionality of controller device1160can be integrated within the handheld device package or provided as a separate attachable device. The interface functionality of controller device1160is implemented using suitable software code for interacting with the user and using the wireless communication capabilities to conduct communications with IPG1100.

Controller device1160preferably provides one or more user interfaces to allow the user to operate pulse generator1100according to one or more stimulation programs to treat the patient's disorder(s). Each stimulation program may include one or more sets of stimulation parameters including pulse amplitude, pulse width, pulse frequency or inter-pulse period, pulse repetition parameter (e.g., number of times for a given pulse to be repeated for respective stimset during execution of program), etc. IPG1100modifies its internal parameters in response to the control signals from controller device1160to vary the stimulation characteristics of stimulation pulses transmitted through stimulation lead1120to the tissue of the patient. Neurostimulation systems, stimsets, and multi-stimset programs are discussed in PCT Publication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,” and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FOR PROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporated herein by reference.