Systems and methods for implanting an electrical stimulation lead using a sheath

A method for implanting an electrical stimulation lead into a patient includes inserting an elongated sheath into a patient. The sheath includes a sheath body with a proximal end and a distal tip. The sheath defines a lumen extending from the proximal end of the sheath to the distal tip. The distal tip of the sheath is advanced to the patient's epidural space. The distal tip of the sheath is positioned at a target implantation location. A lead is advanced along the lumen of the sheath from the proximal end of the sheath body to the distal tip. The lead includes a lead body and a plurality of electrodes disposed along a distal end of the lead body. The sheath is removed from the patient while leaving the distal end of the lead at the target implantation location.

FIELD

The present invention is directed to the area of implantable electrical stimulation systems and methods of making and using the systems. The present invention is also directed to implantation of electrical stimulation leads in proximity to a target stimulation region using a sheath, as well as methods of making and using the sheaths, leads, and electrical stimulation systems.

BACKGROUND

Implantable electrical stimulation systems have proven therapeutic in a variety of diseases and disorders. For example, spinal cord stimulation systems have been used as a therapeutic modality for the treatment of chronic pain syndromes. Peripheral nerve stimulation has been used to treat incontinence, as well as a number of other applications under investigation. Functional electrical stimulation systems have been applied to restore some functionality to paralyzed extremities in spinal cord injury patients.

Stimulators have been developed to provide therapy for a variety of treatments. A stimulator can include a control module (with a pulse generator), one or more leads, and an array of stimulator electrodes on each lead. The stimulator electrodes are in contact with or near the nerves, muscles, or other tissue to be stimulated. The pulse generator in the control module generates electrical pulses that are delivered by the electrodes to body tissue.

Dorsal root ganglia are nodules of cell bodies disposed along the dorsal roots of spinal nerves. Dorsal root ganglia are disposed external to the epidural space. Dorsal root ganglia, however, are disposed in proximity to the spinal cord and the vertebral column.

BRIEF SUMMARY

In one embodiment, a method for implanting an electrical stimulation lead into a patient includes inserting an elongated sheath into a patient. The sheath includes a sheath body with a proximal end and a distal tip. The sheath defines a lumen extending from the proximal end of the sheath to the distal tip. The distal tip of the sheath is advanced to the patient's epidural space. The distal tip of the sheath is positioned at a target implantation location. A lead is advanced along the lumen of the sheath from the proximal end of the sheath body to the distal tip. The lead includes a lead body and a plurality of electrodes disposed along a distal end of the lead body. The sheath is removed from the patient while leaving the distal end of the lead at the target implantation location.

In another embodiment, an insertion kit for facilitating implantation of a percutaneous lead in proximity to a dorsal root ganglion includes a percutaneous lead and an elongated sheath. The percutaneous lead includes a lead body with a proximal end, a distal end, and a longitudinal length. A plurality of electrodes is disposed along the distal end of the lead body. A plurality of terminals is disposed along the proximal end of the lead body. A plurality of conductors electrically couples the plurality of electrodes to the plurality of terminals. The elongated sheath includes a sheath body having a proximal end, a distal tip, and a longitudinal length. A distal opening is disposed at the distal tip of the sheath body. A proximal opening is disposed at the proximal end of the sheath body. A lumen extends between the distal opening and the proximal opening. The lumen forms a continuous passageway along the longitudinal length of the sheath body. The lumen is configured and arranged to receive the lead body.

DETAILED DESCRIPTION

The present invention is directed to the area of implantable electrical stimulation systems and methods of making and using the systems. The present invention is also directed to implantation of electrical stimulation leads in proximity to a target stimulation region using a sheath, as well as methods of making and using the sheaths, leads, and electrical stimulation systems.

Suitable implantable electrical stimulation systems include, but are not limited to, an electrode lead (“lead”) with one or more electrodes disposed on a distal end of the lead and one or more terminals disposed on one or more proximal ends of the lead. Leads include, for example, deep brain stimulation leads, percutaneous leads, paddle leads, and cuff leads. Examples of electrical stimulation systems with leads are found in, for example, U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029; 6,609,032; 6,741,892; 7,244,150; 7,672,734; 7,761,165; 7,949,395; 7,974,706; 8,175,710; 8,224,450; and 8,364,278; and U.S. Patent Application Publication No. 2007/0150036, all of which are incorporated by reference.

FIG. 1illustrates schematically one embodiment of an electrical stimulation system100. The electrical stimulation system100includes a control module (e.g., a stimulator or pulse generator)102and a percutaneous lead103. The lead103includes a plurality of electrodes134that form an array of electrodes133. The control module102typically includes an electronic subassembly110and an optional power source120disposed in a sealed housing114. The lead103includes a lead body106coupling the control module102to the plurality of electrodes134. In at least some embodiments, the lead body106is isodiametric.

The control module102typically includes one or more connector assemblies144into which the proximal end of the lead body106can be plugged to make an electrical connection via connector contacts (e.g.,216inFIG. 2A) disposed in the connector assembly144and terminals (e.g.,210inFIG. 2A) disposed along the lead body106. The connector contacts are coupled to the electronic subassembly110and the terminals are coupled to the electrodes134. Optionally, the control module102may include a plurality of connector assemblies144.

The one or more connector assemblies144may be disposed in a header150. The header150provides a protective covering over the one or more connector assemblies144. The header150may be formed using any suitable process including, for example, casting, molding (including injection molding), and the like. In addition, one or more lead extensions224(seeFIG. 2C) can be disposed between the lead body106and the control module102to extend the distance between the lead body106and the control module102.

The electrical stimulation system or components of the electrical stimulation system, including the lead body106and the control module102, are typically implanted into the body of a patient. The electrical stimulation system can be used for a variety of applications including, but not limited to, spinal cord stimulation, brain stimulation, neural stimulation, muscle activation via stimulation of nerves innervating muscle, and the like.

The electrodes134can be formed using any conductive, biocompatible material. Examples of suitable materials include metals, alloys, conductive polymers, conductive carbon, and the like, as well as combinations thereof. In at least some embodiments, one or more of the electrodes134are formed from one or more of: platinum, platinum iridium, palladium, titanium, or rhenium.

The electrodes of the lead body106are typically disposed in, or separated by, a non-conductive, biocompatible material including, for example, silicone, polyurethane, and the like or combinations thereof. The lead body106may be formed in the desired shape by any process including, for example, molding (including injection molding), casting, and the like. Electrodes and connecting wires can be disposed onto or within a paddle body either prior to or subsequent to a molding or casting process. The non-conductive conductive material typically extends from the distal end of the lead body106to the proximal end of the lead body106.

Terminals (e.g.,210inFIG. 2A) are typically disposed at the proximal end of the lead body106for connection to corresponding conductive contacts (e.g.,216inFIG. 2A) in one or more connector assemblies (e.g.,144inFIG. 1) disposed on, for example, the control module102(or to other devices, such as conductive contacts on a lead extension, an operating room cable, a splitter, an adaptor, or the like).

Conductive wires (see e.g.,508ofFIG. 5B) extend from the plurality of terminals (see e.g.,210inFIG. 2A) to the plurality of electrodes133. Typically, each of the plurality of terminals is electrically coupled to at least one of the plurality of electrodes133. In some embodiments, each of the plurality of terminals is coupled to a single electrode134of the plurality of electrodes133.

The conductive wires may be embedded in the non-conductive material of the lead or can be disposed in one or more lumens (not shown) extending along the lead. In some embodiments, there is an individual lumen for each conductive wire. In other embodiments, two or more conductive wires may extend through a lumen. There may also be one or more lumens (not shown) that open at, or near, the proximal end of the lead, for example, for inserting a stylet rod to facilitate placement of the lead within a body of a patient. Additionally, there may also be one or more lumens (not shown) that open at, or near, the distal end of the lead, for example, for infusion of drugs or medication into the site of implantation of the lead103. The one or more lumens may, optionally, be flushed continually, or on a regular basis, with saline, epidural fluid, or the like. The one or more lumens can be permanently or removably sealable at the distal end.

As discussed above, the lead body106may be coupled to the one or more connector assemblies144disposed on the control module102. The control module102can include any suitable number of connector assemblies144including, for example, two three, four, five, six, seven, eight, or more connector assemblies144. It will be understood that other numbers of connector assemblies144may be used instead. InFIG. 1, the lead body106includes eight terminals that are shown coupled with eight conductive contacts disposed in the connector assembly144.

FIG. 2Ais a schematic side view of one embodiment of a connector assembly144disposed on the control module102. InFIG. 2A, the proximal end306of the lead body106is shown configured and arranged for insertion to the control module102.

InFIG. 2A, the connector assembly144is disposed in the header150. In at least some embodiments, the header150defines a port204into which the proximal end206of the lead body106with terminals210can be inserted, as shown by directional arrows212, in order to gain access to the connector contacts disposed in the connector assembly144.

The connector assembly144includes a connector housing214and a plurality of connector contacts216disposed therein. Typically, the connector housing214defines a port (not shown) that provides access to the plurality of connector contacts216. In at least some embodiments, the connector assembly144further includes a retaining element218configured and arranged to fasten the corresponding lead body106to the connector assembly144when the lead body106is inserted into the connector assembly144to prevent undesired detachment of the lead body106from the connector assembly144. For example, the retaining element218may include an aperture220through which a fastener (e.g., a set screw, pin, or the like) may be inserted and secured against an inserted lead body106.

When the lead body106is inserted into the port204, the connector contacts216can be aligned with the terminals210disposed on the lead body106to electrically couple the control module102to the electrodes (134ofFIG. 1) disposed at a distal end of the lead body106. Examples of connector assemblies in control modules are found in, for example, U.S. Pat. Nos. 7,244,150 and 8,224,450, which are incorporated by reference.

In at least some embodiments, the electrical stimulation system includes one or more lead extensions. The lead body106can be coupled to one or more lead extensions which, in turn, are coupled to the control module102. InFIG. 2B, a lead extension connector assembly222is disposed on a lead extension224. The lead extension connector assembly222is shown disposed at a distal end226of the lead extension224. The lead extension connector assembly222includes a contact housing228. The contact housing228defines at least one port230into which a proximal end206of the lead body106with terminals210can be inserted, as shown by directional arrow238. The lead extension connector assembly222also includes a plurality of connector contacts240. When the lead body106is inserted into the port230, the connector contacts240disposed in the contact housing228can be aligned with the terminals210on the lead body106to electrically couple the lead extension224to the electrodes (134ofFIG. 1) disposed at a distal end (not shown) of the lead body106.

The proximal end of a lead extension can be similarly configured and arranged as a proximal end of a lead body. The lead extension224may include a plurality of conductive wires (not shown) that electrically couple the connector contacts240to terminal on a proximal end248of the lead extension224. The conductive wires disposed in the lead extension224can be electrically coupled to a plurality of terminals (not shown) disposed on the proximal end248of the lead extension224. In at least some embodiments, the proximal end248of the lead extension224is configured and arranged for insertion into a lead extension connector assembly disposed in another lead extension. In other embodiments (as shown inFIG. 2B), the proximal end248of the lead extension224is configured and arranged for insertion into the connector assembly144disposed on the control module102.

Turning toFIG. 3A, in at least some embodiments one or more dorsal root ganglia (“DRG”) are potential target stimulation locations.FIG. 3Aschematically illustrates a transverse cross-sectional view of a spinal cord302surrounded by dura304. The spinal cord302includes a midline306and a plurality of levels from which spinal nerves312aand312bextend. In at least some spinal cord levels, the spinal nerves312aand312bextend bilaterally from the midline306of the spinal cord302. InFIG. 3A, the spinal nerves312aand312bare shown attaching to the spinal cord302at a particular spinal cord level via corresponding dorsal roots314aand314band corresponding ventral (or anterior) roots316aand316b. Typically, the dorsal roots314aand314brelay sensory information into the spinal cord302and the ventral roots316aand316brelay motor information outward from the spinal cord302. The DRG320aand320bare nodules of cell bodies that are disposed along the dorsal roots316aand316bin proximity to the spinal cord302.

FIG. 3Bschematically illustrates a perspective view of a portion of the spinal cord302disposed along a portion of a vertebral column330. The vertebral column330includes stacked vertebrae, such as vertebrae332aand332b, and a plurality of DRGs320aand320bextending outwardly bilaterally from the spinal cord302at different spinal cord levels.

FIG. 3Cschematically illustrates a top view of a portion of the spinal cord302and surrounding dura304disposed in a vertebral foramen340defined in the vertebra332b. The vertebrae, such as the vertebrae332aand332b, are stacked together and the vertebral foramina340of the vertebrae collectively form a spinal canal through which the spinal cord302extends. The space within the spinal canal between the dura304and the walls of the vertebral foramen340defines the epidural space342. Intervertebral foramina346aand346b, defined bilaterally along sides of the vertebra332b, form openings through the vertebra332bbetween the epidural space342and the environment external to the vertebra332b.

FIG. 3Dschematically illustrates a side view of two vertebrae332aand332bcoupled to one another by a disc344. InFIG. 3D, the intervertebral foramen346bis shown defined between the vertebrae332aand332b. The intervertebral foramen346bprovides an opening for one or more of the dorsal root314b, ventral root316b, and DRG320bto extend outwardly from the spinal cord302to the environment external to the vertebrae332aand332b.

Turning toFIG. 4A, although the DRG are not within the epidural space, the DRG may be accessible to a lead from within the epidural space via the intervertebral foramina. In at least some embodiments, once the distal end of the lead is inserted into the epidural space the distal end of the lead can be advanced out of the epidural space through one of the intervertebral foramen, and positioned in proximity to the desired DRG.

As herein described, a sheath may be used to facilitate implantation of a lead in proximity to a DRG via the patient's epidural space. In at least some embodiments, an insertion kit for implanting a percutaneous lead into a patient includes the lead and the sheath for facilitating implantation of the lead.

FIG. 4Ais a schematic perspective view of one embodiment of a sheath402suitable for insertion into a patient. The sheath402includes a sheath body404having a distal tip406and an opposing proximal end408. The sheath402defines a lumen412extending between a distal opening414defined at the distal tip406and a proximal opening416defined at the proximal end408. In at least some embodiments, the lumen412defines a continuous passageway extending between the distal opening414and the proximal opening416.

The sheath body404can be rigid, flexible, or a combination thereof. The body404can be formed from any material (e.g., metals, alloys, composites, plastics, or the like) suitable for insertion into a patient. Optionally, the body404may include radiopaque material to facilitate determination of the positioning of the sheath402, for example, when the sheath402is disposed in the patient through medical imaging.

Turning toFIG. 4B, the lumen412is configured and arranged to receive a lead. The lumen412can have any suitable transverse cross-sectional shape including, for example, round, oval, triangular, rectangular, or the like. In at least some embodiments, the transverse cross-sectional shape of the lumen412corresponds with a transverse cross-sectional shape of an outer surface of a widest portion of the lead to be inserted into the lumen412.

FIG. 4Bis a schematic perspective view of one embodiment of a portion of a lead420extending along the lumen412. The lead420includes a lead body422with a distal end424. A plurality of electrodes, such as electrode426, is disposed along the distal end424of the lead body422. In at least some embodiments, the lead420is a percutaneous lead (see e.g.,FIG. 1). In at least some embodiments, the lead body422is isodiametric. InFIG. 4B, the distal end424of the lead420and at least some of the electrodes426are shown extending distally outward from the lumen412.

In at least some embodiments, at least one of the plurality of electrodes426is configured as a ring electrode that extends completely around a radius of curvature of the lead body422. In at least some other embodiments, at least one of the plurality of the electrodes426is configured such that the at least one electrode426extends around less than complete revolution about the lead body422. For example, at least one of the plurality of electrodes426may be formed as a segmented electrode, a cuff-shaped electrode, an arc-shaped electrode, a tip electrode, or the like. It may be advantageous to form one or more of the electrodes426such that the one or more electrodes426extend around less than complete revolution about the lead body422so that energy propagated from the one or more electrodes426can be directed primarily in the direction of the target stimulation location.

As mentioned above, in at least some embodiments the sheath body404is rigid. As discussed in more detail below, with reference toFIGS. 6A-6B, in at least some embodiments the sheath402is used to form an incision in the patient extending from an external location on the patient to the patient's epidural space. In which case, it may be beneficial for the sheath body404to be sufficiently rigid to form the incision. In embodiments where the sheath is used to form an incision through patient tissue it may, additionally, be beneficial for the distal tip406of the sheath to be sufficiently sharp to pierce patient skin and to advance through patient tissue.

In at least some embodiments, it may be beneficial to insert a plug into the lumen412of the sheath402during, for example, advancement of the sheath402into the epidural space to reduce or prevent coring of patient tissue.FIG. 4Cis a schematic perspective view of one embodiment of a plug444inserted into the sheath402. In at least some embodiments, the plug444has a tip446disposed in proximity to the distal tip406of the sheath402and an elongated tail448that is reachable by a practitioner from the proximal end408of the sheath. The tip446can be either blunt or sharp.

In at least some embodiments, the plug444is formed as one of an obturator, a trocar, a stylet, or the like. In at least some embodiments, the plug444is also used to provide rigidity to the sheath402to facilitate advancement. In at least some embodiments, the plug444is disposed in the lumen412of the sheath402during advancement of the sheath402through patient tissue. In which case, the plug444may be removed prior to inserting the lead420into the lumen412, when less rigidity is needed.

Turning toFIGS. 5A-5D, in at least some embodiments the sheath402is configured and arranged to be advanced to a target implantation location. The target implantation location may be the target stimulation location (e.g., the DRG), or another nearby location (e.g., the epidural space). In some instances, the target implantation location may not be conveniently accessible from an external location on the patient via a straight line. Accordingly, it may be advantageous for the sheath to include at least one bend. It may also be advantageous for the sheath to be flexible, or to include one or more flexible regions, to enable the sheath to negotiate one or more anatomical curves during advancement to the target implantation location.

FIG. 5Ais a schematic perspective view of another embodiment of the sheath402that includes a flexible region502intermediate to the distal tip406and the proximal end408of the sheath402. InFIG. 5A, the flexible region502is disposed in a straight configuration.FIG. 5Bis a schematic perspective view of one embodiment of the sheath402with the flexible region502transitioned into a bent position such that the sheath402includes at least one bend504.

It will be understood that the one or more flexible regions502are relatively flexible, as compared to the remaining portions of the sheath body404. In at least some embodiments, the one or more flexible regions502are sufficiently flexible to enable a practitioner to bend the one or more flexible regions502into a desired angle immediately prior to (or during) an implantation procedure. In at least some embodiments, the one or more flexible regions502are sufficiently rigid enough to maintain the shape of the one or more bends504formed along the flexible regions502during the implantation procedure.

In at least some embodiments, the sheath includes one or more pre-defined bends formed along the sheath body.FIG. 5Cis a schematic perspective view of yet another embodiment of the sheath402. A pre-defined bend506is formed along the sheath body404. The pre-defined bend506can be formed along any portion of the sheath body404. In at least some embodiments, the pre-defined bend506is formed along the sheath402intermediate to the distal tip406and the proximal end408of the sheath402. In at least some embodiments, a pre-defined bend is formed at the distal tip406of the sheath402. It may be advantageous to form the pre-defined bend404at the distal tip406, or in proximity to the distal tip406, to facilitate advancement of the sheath404within the patient.

The sheath402can include one or more pre-defined bends504, one or more flexible regions502, or both.FIG. 5Cshows the sheath402also including a flexible region502in addition to the pre-defined bend504. InFIG. 5C, the flexible region502is disposed in a straight configuration along the distal tip406of the sheath body404.FIG. 5Dis a schematic perspective view of one embodiment of the sheath402with the flexible region502moved into a bent position such that the sheath402includes at least one bend504.

In at least some embodiments, the sheath402includes exactly one flexible region502. In at least some embodiments, the sheath402includes a plurality of flexible regions502. In at least some embodiments, the one or more flexible regions502are configured and arranged to enable the sheath502to be bent to form an angle that is no less than 1°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or more. In at least some embodiments, the one or more flexible regions502are configured and arranged to enable the sheath502to be bent to form an angle that is no greater than 160°, 150°, 140°, 130°, 120°, 110°, 100°, 90°, 80°, 70°, 60°, 50°, 40°, 30°, 20°, 10°, 1°, or less.

Any suitable number of pre-defined bends can be formed along the sheath body404. The one or more pre-defined bends506may be formed in addition to, or in lieu of, the one or more bends504that are formable along a flexible region502of the sheath402. In at least some embodiments, the one or more pre-defined bends each form an angle that is no less than 1°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, or more. In at least some embodiments, the one or more pre-defined bends each form an angle that is no greater than 160°, 150°, 140°, 130°, 120°, 110°, 100°, 90°, 80°, 70°, 60°, 50°, 40°, 30°, 20°, 10°, 1°, or less.

In at least some embodiments, the one or more pre-defined bends are formed during manufacture or prior to distribution to practitioners. In at least some embodiments, the one or more pre-defined bends are angled such that the pre-defined bends are configured and arranged for insertion into the epidural space from a location external to the patient. In at least some embodiments, the one or more pre-defined bends are angled such that the pre-defined bends are configured and arranged for insertion into an intervertebral foramen from inside the epidural space.

Turning toFIGS. 6A-7B, in at least some embodiments the target implantation location is a location in proximity to the target stimulation location. For example, in at least some embodiments the target implantation location is the epidural space.FIG. 6Ais a schematic perspective view of the spinal cord302disposed along a longitudinal transverse view of a portion of the vertebral column330. The portion of the vertebral column330shown inFIG. 6Aincludes the vertebrae332aand332band intervertebral foramina346aand346bdefined between the vertebrae332aand332bon opposing sides of the vertebral column330. The DRG320extends outward from one side of the spinal cord302and through the intervertebral foramen346b.

InFIG. 6A, the distal tip406of the sheath402is shown disposed in the epidural space342. In at least some embodiments, a bend602is formed along the sheath402. The bend602enables the distal tip406of the sheath402to be re-oriented from its trajectory entering the epidural space342to correspond with the directionality of the epidural space342. The bend602can be either a pre-defined bend (see e.g., bend506) or a bend formed along a flexible region (see e.g., bend504). In some embodiments, a single bend is formed along the sheath402. Alternately, two or more bends may be formed along the sheath402. In at least some embodiments, the sheath402is steerable to facilitate advancement of the sheath to the target implantation location. The sheath402can be steered in any suitable manner including, for example, using a stylet, a guidewire, or the like.

The sheath402can be advanced into the epidural space342in any suitable manner. The sheath402can be inserted into the epidural space342using a fully or partially pre-formed incision extending between the epidural space and an external location on the patient, or the sheath402can be used to form all, or a portion of the incision extending between the epidural space and an external location on the patient.

In at least some embodiments, the sheath402is advanced along the incision by itself. Optionally, the plug (444inFIG. 4C) may be disposed in the sheath402during insertion into the epidural space342to reduce or prevent coring of patient tissue, or to provide stiffness to the sheath402(if needed), or both. Alternately, instead of inserting the plug into the sheath402, in at least some embodiments a guide wire, a dilator, or the like may be inserted into the sheath402during at least a portion of the advancement of the sheath402to the target implantation location. Optionally, the sheath402may be inserted into a percutaneous needle and advanced at least partially through the incision while disposed in the percutaneous needle. In at least some embodiments, a dilator is used to enlarge a pre-formed incision prior to the advancement of the sheath402along the incision.

In at least some embodiments, instead of inserting the plug into the sheath402the lead420is disposed in the sheath402when the sheath402is advanced into the epidural space342. In which case, the sheath402functions as a stiffener for the lead420. Additionally, the sheath402may provide a broader working space for potential lead designs as the lead420may not have to satisfy as many requirements, as compared to conventional percutaneous lead implantation procedures. For example, the sheath402may support one or more deployable features on or in the lead420. Moreover, for example, the sheath402may provide protection for one or more delicate features disposed on, or in, the lead420.

In at least some embodiments, once the distal tip406of the sheath402is disposed at the target implantation location (e.g., the epidural space342), the lead420is advanced along the lumen412of the sheath402to the distal tip406and the sheath402is removed from the patient, leaving the distal end of the lead420disposed in the epidural space342. In at least some embodiments, the lead420is sufficiently stiff to be advanced along the sheath402without providing a stiffener. In other embodiments, the lead420is advanced along the sheath402with the aid of one or more stiffeners, such as a guidewire, a stylet, or the like.

In at least some embodiments, once the distal end of the lead420is disposed at the target implantation location (e.g., the epidural space342) and the sheath402is removed, the lead420is advanced to the target stimulation location without the sheath402.FIG. 6Billustrates the distal end of the lead420positioned near the DRG320such that the electrodes426of the lead420are in operational proximity to the DRG320. When, as shown inFIG. 6B, the target stimulation location is the DRG320, the lead420can be advanced out of the epidural space342, via the intervertebral foramen346b. The lead420can be guided in any suitable manner including, for example, using a stylet, a guidewire, or the like.

In at least some embodiments, the target implantation location for the sheath is the target stimulation location (e.g., the DRG).FIG. 7Ais a schematic perspective view of the sheath402inserted into the epidural space342and the distal tip406of the sheath402advanced out through the intervertebral foramen346band positioned in proximity to the DRG320. In at least some embodiments, the sheath402is steerable to facilitate advancement of the sheath to the target implantation location. The sheath402can be steered in any suitable manner including, for example, using a stylet, a guidewire, or the like.

The sheath402may include any suitable number of bends602for facilitating advancement of the sheath402to the target implantation location. InFIG. 6B, the sheath402is shown with two bends602. In at least some embodiments, one or more of the bends are used to temporarily anchor the sheath402to the vertebral column330until the lead420is advanced to the target stimulation location.

Once the distal tip of the sheath402is positioned, the lead420is advanced along the sheath402to the distal tip406and the sheath402is removed from the patient.FIG. 7Billustrates the distal end of the lead420positioned near the DRG320such that the electrodes426of the lead420are in operational proximity to the DRG320. As mentioned above, in at least some embodiments the lead420is sufficiently stiff to be advanced along the sheath402without providing a stiffener. In other embodiments, the lead420is advanced along the sheath402with the aid of a guidewire, stylet, or the like.

It may be advantageous to advance the sheath402to the target stimulation location. When the sheath402is advanced all the way to the target stimulation location, the lead420can be positioned at the target stimulation location without needing to separately advance the sheath402part of the way to the target stimulation location, and then advance the lead420the rest of the way to the target stimulation location. Additionally, advancing the lead420all of the way to the target stimulation location from within the sheath402enables the lead420to be formed all, or in part, from a flexible (e.g., floppy) material that may otherwise be difficult to advance to the target stimulation location using conventional techniques.

FIG. 8is a schematic overview of one embodiment of components of an electrical stimulation system800including an electronic subassembly810disposed within a control module. It will be understood that the electrical stimulation system can include more, fewer, or different components and can have a variety of different configurations including those configurations disclosed in the stimulator references cited herein.

Some of the components (for example, power source812, antenna818, receiver802, and processor804) of the electrical stimulation system can be positioned on one or more circuit boards or similar carriers within a sealed housing of an implantable pulse generator, if desired. Any power source812can be used including, for example, a battery such as a primary battery or a rechargeable battery. Examples of other power sources include super capacitors, nuclear or atomic batteries, mechanical resonators, infrared collectors, thermally-powered energy sources, flexural powered energy sources, bioenergy power sources, fuel cells, bioelectric cells, osmotic pressure pumps, and the like including the power sources described in U.S. Pat. No. 7,437,193, incorporated herein by reference.

As another alternative, power can be supplied by an external power source through inductive coupling via the optional antenna818or a secondary antenna. The external power source can be in a device that is mounted on the skin of the user or in a unit that is provided near the user on a permanent or periodic basis.

If the power source812is a rechargeable battery, the battery may be recharged using the optional antenna818, if desired. Power can be provided to the battery for recharging by inductively coupling the battery through the antenna to a recharging unit816external to the user. Examples of such arrangements can be found in the references identified above.

In one embodiment, electrical current is emitted by the electrodes134on the paddle or lead body to stimulate nerve fibers, muscle fibers, or other body tissues near the electrical stimulation system. A processor804is generally included to control the timing and electrical characteristics of the electrical stimulation system. For example, the processor804can, if desired, control one or more of the timing, frequency, strength, duration, and waveform of the pulses. In addition, the processor804can select which electrodes can be used to provide stimulation, if desired. In some embodiments, the processor804may select which electrode(s) are cathodes and which electrode(s) are anodes. In some embodiments, the processor804may be used to identify which electrodes provide the most useful stimulation of the desired tissue.

Any processor can be used and can be as simple as an electronic device that, for example, produces pulses at a regular interval or the processor can be capable of receiving and interpreting instructions from an external programming unit808that, for example, allows modification of pulse characteristics. In the illustrated embodiment, the processor804is coupled to a receiver802which, in turn, is coupled to the optional antenna818. This allows the processor804to receive instructions from an external source to, for example, direct the pulse characteristics and the selection of electrodes, if desired.

In one embodiment, the antenna818is capable of receiving signals (e.g., RF signals) from an external telemetry unit806which is programmed by a programming unit808. The programming unit808can be external to, or part of, the telemetry unit806. The telemetry unit806can be a device that is worn on the skin of the user or can be carried by the user and can have a form similar to a pager, cellular phone, or remote control, if desired. As another alternative, the telemetry unit806may not be worn or carried by the user but may only be available at a home station or at a clinician's office. The programming unit808can be any unit that can provide information to the telemetry unit806for transmission to the electrical stimulation system800. The programming unit808can be part of the telemetry unit806or can provide signals or information to the telemetry unit806via a wireless or wired connection. One example of a suitable programming unit is a computer operated by the user or clinician to send signals to the telemetry unit806.

The signals sent to the processor804via the antenna818and receiver802can be used to modify or otherwise direct the operation of the electrical stimulation system. For example, the signals may be used to modify the pulses of the electrical stimulation system such as modifying one or more of pulse duration, pulse frequency, pulse waveform, and pulse strength. The signals may also direct the electrical stimulation system800to cease operation, to start operation, to start charging the battery, or to stop charging the battery. In other embodiments, the stimulation system does not include an antenna818or receiver802and the processor804operates as programmed.

Optionally, the electrical stimulation system800may include a transmitter (not shown) coupled to the processor804and the antenna818for transmitting signals back to the telemetry unit806or another unit capable of receiving the signals. For example, the electrical stimulation system800may transmit signals indicating whether the electrical stimulation system800is operating properly or not or indicating when the battery needs to be charged or the level of charge remaining in the battery. The processor804may also be capable of transmitting information about the pulse characteristics so that a user or clinician can determine or verify the characteristics.