Abstract:
Devices, systems and methods are provided for stimulation of tissues and structures within a body of a patient. In particular, implantable leads are provided which are comprised of a flexible circuit. Typically, the flexible circuit includes an array of conductors bonded to a thin dielectric film. Example dielectric films include polyimide, polyvinylidene fluoride (PVDF) or other biocompatible materials to name a few. Such leads are particularly suitable for stimulation of the spinal anatomy, more particularly suitable for stimulation of specific nerve anatomies, such as the dorsal root (optionally including the dorsal root ganglion).

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/952,062, filed Dec. 6, 2007, which claims priority of U.S. Provisional Patent Application No. 60/873,459, filed Dec. 6, 2006 (Atty. Docket No. 10088-702.101); and U.S. Provisional Patent Application No. 60/873,496, filed Dec. 6, 2006 (Atty. Docket No. 10088-704.101), both of which are incorporated herein by reference for all purposes. 
     
    
     BACKGROUND 
       [0002]    The application of specific electrical energy to the spinal cord for the purpose of managing pain has been actively practiced since the 1960s. It is known that application of an electrical field to spinal nervous tissue can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nervous tissue. Such masking is known as paresthesia, a subjective sensation of numbness or tingling in the afflicted bodily regions. Application of electrical energy has been based on the gate control theory of pain. Published in 1965 by Melzack and Wall, this theory states that reception of large nerve fiber information, such as touch, sense of cold, or vibration, would turn off or close the gate to reception of painful small nerve fiber information. The expected end result would, therefore, be pain relief. Based on the gate control theory, electrical stimulation of large fibers of the spinal cord cause small fiber information to be reduced or eliminated at that spinal segment and all other information downstream from that segment would be reduced or eliminated as well. Such electrical stimulation of the spinal cord, once known as dorsal column stimulation, is now referred to as spinal cord stimulation or SCS. 
         [0003]      FIGS. 1A-1B  illustrate conventional placement of an SCS system  10 . Conventional SCS systems include an implantable power source or implantable pulse generator (IPG)  12  and an implantable lead  14 . Such IPGs  12  are similar in size and weight to pacemakers and are typically implanted in the buttocks of a patient P. Using fluoroscopy, the lead  14  is implanted into the epidural space E of the spinal column and positioned against the dura layer D of the spinal cord S, as illustrated in  FIG. 1B . The lead  14  is implanted either through the skin via an epidural needle (for percutaneous leads) or directly and surgically through a mini laminotomy operation (for paddle leads). 
         [0004]      FIG. 2  illustrates example conventional paddle leads  16  and percutaneous leads  18 . Paddle leads  16  typically have the form of a slab of silicon rubber having one or more electrodes  20  on its surface. Example dimensions of a paddle lead  16  is illustrated in  FIG. 3 . Percutaneous leads  18  typically have the form of a tube or rod having one or more electrodes  20  extending therearound. Example dimensions of a percutaneous lead  18  is illustrated in  FIG. 4 . 
         [0005]    Implantation of a percutaneous lead  18  typically involves an incision over the low back area (for control of back and leg pain) or over the upper back and neck area (for pain in the arms). An epidural needle is placed through the incision into the epidural space and the lead is advanced and steered over the spinal cord until it reaches the area of the spinal cord that, when electrically stimulated, produces a comfortable tingling sensation (paresthesia) that covers the patient&#39;s painful area. To locate this area, the lead is moved and turned on and off while the patient provides feedback about stimulation coverage. Because the patient participates in this operation and directs the operator to the correct area of the spinal cord, the procedure is performed with local anesthesia. 
         [0006]    Implantation of paddle leads  16  typically involves performing a mini laminotomy to implant the lead. An incision is made either slightly below or above the spinal cord segment to be stimulated. The epidural space is entered directly through the hole in the bone and a paddle lead  16  is placed over the area to stimulate the spinal cord. The target area for stimulation usually has been located before this procedure during a spinal cord stimulation trial with percutaneous leads  18 . 
         [0007]    Although such SCS systems have effectively relieved pain in some patients, these systems have a number of drawbacks. To begin, as illustrated in  FIG. 5 , the lead  14  is positioned upon the spinal cord dura layer D so that the electrodes  20  stimulate a wide portion of the spinal cord and associated spinal nervous tissue. The spinal cord is a continuous body and three spinal levels of the spinal cord are illustrated. For purposes of illustration, spinal levels are sub-sections of the spinal cord S depicting that portion where the dorsal root DR and ventral root VR join the spinal cord S. The peripheral nerve N divides into the dorsal root DR and the dorsal root ganglion DRG and the ventral nerve root VR each of which feed into the spinal cord S. An ascending pathway  17  is illustrated between level  2  and level  1  and a descending pathway  19  is illustrated from level  2  to level  3 . Spinal levels can correspond to the vertebral levels of the spine commonly used to describe the vertebral bodies of the spine. For simplicity, each level illustrates the nerves of only one side and a normal anatomical configuration would have similar nerves illustrated in the side of the spinal cord directly adjacent the lead. 
         [0008]    Motor spinal nervous tissue, or nervous tissue from ventral nerve roots, transmits muscle/motor control signals. Sensory spinal nervous tissue, or nervous tissue from dorsal nerve roots, transmits pain signals. Corresponding dorsal and ventral nerve roots depart the spinal cord “separately”; however, immediately thereafter, the nervous tissue of the dorsal and ventral nerve roots are mixed, or intertwined. Accordingly, electrical stimulation by the lead  14  often causes undesirable stimulation of the motor nerves in addition to the sensory spinal nervous tissue. 
         [0009]    Because the electrodes span several levels the generated stimulation energy  15  stimulates or is applied to more than one type of nerve tissue on more than one level. Moreover, these and other conventional, non-specific stimulation systems also apply stimulation energy to the spinal cord and to other neural tissue beyond the intended stimulation targets. As used herein, non-specific stimulation refers to the fact that the stimulation energy is provided to all spinal levels including the nerves and the spinal cord generally and indiscriminately. Even if the epidural electrode is reduced in size to simply stimulate only one level, that electrode will apply stimulation energy Indiscriminately to everything (i.e. all nerve fibers and other tissues) within the range of the applied energy. Moreover, larger epidural electrode arrays may after cerebral spinal fluid flow thus further altering local neural excitability states. 
         [0010]    Another challenge confronting conventional neurostimulation systems is that since epidural electrodes must apply energy across a wide variety of tissues and fluids (i.e. CSF fluid amount varies along the spine as does pia mater thickness) the amount of stimulation energy needed to provide the desired amount of neurostimulation is difficult to precisely control. As such, increasing amounts of energy may be required to ensure sufficient stimulation energy reaches the desired stimulation area. However, as applied stimulation energy increases so too increases the likelihood of deleterious damage or stimulation of surrounding tissue, structures or neural pathways. 
         [0011]    Improved stimulation devices, systems and methods are desired that enable more precise and effective delivery of stimulation energy. Such devices should be reliably manufactural, appropriately sized, cost effective and easy to use. At these some of these objectives will be fulfilled by the present invention. 
       SUMMARY 
       [0012]    The present invention provides devices, systems and methods for stimulation of tissues and structures within a body of a patient. In particular, implantable leads are provided which are flexible, reliable and easily manufacturable for a variety of medical applications. Such leads are particularly suitable for stimulation of the spinal anatomy, more particularly suitable for stimulation of specific nerve anatomies, such as the dorsal root (optionally including the dorsal root ganglion). Such specificity is enhanced by the design attributes of the leads. 
         [0013]    The implantable leads of the present invention utilize a flexible circuit. Typically, the flexible circuit includes an array of conductors bonded to a thin dielectric film. Example dielectric films include polyimide, polyvinylidene fluoride (PVDF) or other biocompatible materials to name a few. The conductors are comprised of biocompatible conductive metal(s) and/or alloy(s), such as gold, titanium, tungsten, titanium tungsten, titanium nitride, platinum, iridium, or platinum-iridium alloy, which is plated onto the dielectric film. The base and metal construct is then etched to form a circuit (i.e. an electrode pad contact and a “trace” to connect the pad to a connector). In some embodiments, redundancy in the “traces” is provided by utilizing multiple traces to the same contact to improve reliability. 
         [0014]    Some advantages of leads comprised of a flexible circuit over traditional leads are greater reliability, size and weight reduction, elimination of mechanical connectors, elimination of wiring errors, increased impedance control and signal quality, circuit simplification, greater operating temperature range, and higher circuit density. In addition, lower cost is another advantage of using flexible circuits. In some embodiments, the entire lead will be formed from a flexible circuit. Also, in some embodiments, the lead will include an integrated connector for connection to an electronics package. 
         [0015]    One main advantage of the flexible circuitry lead is its thinness and therefore flexibility. The thickness of the dielectric film typically ranges from 7.5 to 125 μm (0.3 to 5 mils). However, in some embodiments, the lead will be comprised of a flexible circuit having a base layer of 0.5 to 2 mils thick. 
         [0016]    The flexible circuitry used in the present invention may be single-sided, double-sided, or multilayer. Single-sided circuits are comprised of a single conductive layer and are the simplest type of flexible circuit. In some instances, a technique known as back baring or double access may be used to create a special type of single layer circuit. This technique allows access to the metal conductors from both sides of the circuit and is used when component soldering or other interconnection is desired on two sides of the circuit. 
         [0017]    Double-sided circuits, as the name implies, are circuits with two conductive layers that are usually accessible from both sides. Multilayer refers to two or more layers which have been stacked and bonded. 
         [0018]    In some embodiments, the flexible circuit is created with methods of the present invention. For example, metal deposition, such as vapor deposition, sputtering techniques or plasma fields, is used to coat the film structure with metal to form the electrodes and traces. In such embodiments, the film structure is comprised of polyvinylidene fluoride (PVDF). The process may utilize PVDF in either sheet form or, preferably, in roll form, with cooling to reduce thermal stresses between the dielectric film structure and the metal coat. The PVDF is coated with an adhesion layer, such as titanium or titanium-tungsten alloy, which will improve the reliability of the bond between the dielectric film structure and the electrodes and traces that will be deposited thereon. The adhesion layer is then coated, such as sputter coated, with a seed layer of conductive biocompatible metal, such as gold or platinum. After such metallization, the seed layer is patterned, either by photolithography and wet etch, or by laser ablation to form the shapes of the traces and electrodes. After patterning the seed layer of metal, sputtering or electroplating is used to increase the thickness of the traces in order to improve conductivity, and then again to create the final electrode working surface. Possible trace materials include platinum, gold, iridium-oxide, a combination thereof or any other conductive biocompatible metal suitable for implantation. The electrode surface may be coated over the entire metallization of the lead, or selectively and only over the intended electrode surface with an inert metal such as platinum, iridium-oxide, or combination thereof. In some embodiments, the adhesion layer of titanium or titanium-tungsten alloy is sputter coated with a seed layer of gold, then sputter coated with platinum and then electroplated with platinum. In other embodiments, the adhesion layer of titanium or titanium-tungsten alloy is sputter coated with a seed layer of gold, then electroplated with gold and then electroplated with platinum. In yet other embodiments, the adhesion layer of titanium or titanium-tungsten alloy is sputter coated with a seed layer of platinum, then electroplated with platinum. It may be appreciated that other combinations may also be used. 
         [0019]    In a first aspect of the present invention, a method is provided for stimulating a tissue within a body. In some embodiments, the method comprises positioning a lead comprising a flexible circuit having at least one electrode so that at least one of the at least one electrode is disposed near a dorsal root. Optionally, the positioning ensures that at least one of the at least one electrode is disposed near a dorsal root ganglion of the dorsal root. The method also includes supplying electrical energy to the at least one of the at least one electrode so as to stimulate at least a portion of the dorsal root. In some embodiments, the portion of the dorsal root comprises a dorsal root ganglion. 
         [0020]    Optionally, the method may include advancing the lead through a foramen and/or advancing the lead through an epidural space. Typically, the method further comprises joining the lead with an implantable pulse generator. In such instances, the method typically includes implanting the lead and the implantable pulse generator wholly within the body. 
         [0021]    In a second aspect of the present invention, a flexible circuit lead is provided for stimulating a body tissue. In some embodiments, the lead comprises an elongate structure having a distal end configured to be positioned near a dorsal root and a proximal end coupleable with a pulse generator, wherein the structure comprises a dielectric film. The lead also includes at least one electrode disposed near the distal end and at least one conductive trace extending from the at least one electrode toward the proximal end so that stimulation energy is transmittable from the coupled pulse generator to the at least one electrode so as to stimulate the at least a portion of the dorsal root. 
         [0022]    In some embodiments, the at least one electrode is comprised of a biocompatible conductive metal, alloy or combination of these plated onto the dielectric film. In such instances, the biocompatible conductive metal, alloy or combination may include gold, titanium, tungsten, titanium tungsten, titanium nitride, platinum, iridium or platinum-iridium alloy. Often, the dielectric film has a thickness in the range of approximately 7.5 to 125 μm. 
         [0023]    In some embodiments, the at least one electrode comprises a plurality of electrodes arranged substantially linearly along a longitudinal axis of the distal end. In other embodiments, the at least one electrode comprises a plurality of electrodes arranged substantially linearly along a horizontal axis of the distal end. Optionally, the at least one electrode comprises a plurality of electrodes arranged in a substantially circular or arc shape. 
         [0024]    In some instances, the distal end has a pronged shape including at least two prongs. In such instances, one of the at least one electrodes may be disposed near a tip of one of the at least two prongs. In some embodiments, the distal end is configured to wrap around the body tissue. And typically, the distal end of the elongate structure is passable through a needle. 
         [0025]    In a third aspect of the present invention, a lead is provided for stimulating a body tissue comprising: an elongate structure having a proximal end coupleable with a pulse generator and a distal end having two edges which are capable of being positioned in opposition, wherein the distal end includes at least two electrodes which generally oppose each other when the edges are positioned in opposition so as to stimulate the body tissue. Typically the body tissue comprises a dorsal root ganglion. 
         [0026]    In some embodiments, the distal end forms a V-shape or U-shape when the two edges are positioned in opposition which allows the body tissue to be positioned at least partially within the V-shape or U-shape. The distal end may comprise two elongate elements, each element having one of the two edges. In such instances, the two elongate elements may be positionable in linear alignment with a longitudinal axis of the elongate structure. 
         [0027]    In some embodiments, the distal end has a rounded shape wherein sides of the rounded shape form the two edges. In such embodiments, the sides of the rounded shape may curl or fold towards each other to position the two edges in opposition. 
         [0028]    Typically, the elongate structure comprises a dielectric film. The dielectric film may have a thickness in the range of approximately 7 to 125 μm. Also, the at least two electrodes may be comprised of a biocompatible conductive metal, alloy or combination of these plated on the dielectric film. Typically, the distal end is passable through a needle. 
         [0029]    In another aspect of the present invention, a system for stimulating a body tissue is provided comprising: a first elongate structure having first proximal end coupleable with a pulse generator and a first distal end, wherein the first distal end has a first inner surface having a first electrode disposed thereon, and a second elongate structure having a second proximal end coupleable with the pulse generator and a second distal end, wherein the second distal end has a second inner surface having a second electrode disposed thereon. The first and second elongate structures are joined so that the first and second electrodes are capable of directing stimulation energy toward each other, and wherein the first and second distal ends are moveable away from each other so as to allow the body tissue to be positioned at least partially therebetween to receive the stimulation energy. 
         [0030]    In some embodiments, the first and second elongate structures are slidably joined. Optionally, the first distal end is movable by recoil force. In some systems, the first distal end is attachable to a first obturator which is capable of moving the first distal end. In these systems, the first obturator may be configured to dissect tissue while it moves the first distal end. Optionally, the first obturator may be advanceable from a delivery device so as to advance the first distal end and move the first distal end away from the second distal end. 
         [0031]    Typically, the first elongate structure comprises a dielectric film. And, typically, the body tissue comprises a dorsal root ganglion. Optionally, the distal end may be passable through a needle. 
         [0032]    In some embodiments, the first elongate structure includes a first contact pad disposed on an outer surface of the proximal end of the first elongate structure, wherein the first contact pad provides electrical connection from the first electrode to the pulse generator. And in some embodiments, the second elongate structure includes a second contact pad disposed on an outer surface of the proximal end of the second elongate structure, wherein the second contact pad provides electrical connection from the second electrode to the pulse generator. 
         [0033]    In another aspect of the present invention, a flexible circuit lead is provided for stimulating a body tissue, wherein the lead comprises an elongate structure having a distal end comprising at least one electrode on a dielectric film, and wherein the distal end is movable to at least partially surround the body tissue and direct stimulation energy from the at least one electrode toward the body tissue. Typically, the distal end is passable through a needle. 
         [0034]    In some embodiments, the distal end is moveable by curling or uncurling so as to at least partially surround the body tissue. In other embodiments, the distal end is moveable by folding or unfolding so as to at least partially surround the body tissue. 
         [0035]    Typically, the distal end comprises opposing elements which move toward or away from each other so as to at least partially surround the body tissue. In some instances, the opposing elements may move independently. Optionally, the opposing elements may form a V-shape. 
         [0036]    In another aspect of the present invention, a device is provided for stimulating a body tissue, wherein the device comprises an elongate shaft having an outer surface and a lead having a at least one electrode, wherein the lead is mounted on the outer surface of the elongate shaft so that the at least one electrode is positionable near a dorsal root for stimulation. Typically, the lead is comprised of an elongate structure comprising a dielectric film. In such instances, the at least one electrode may be comprised of a biocompatible conductive metal, alloy or combination of these plated onto the dielectric film. 
         [0037]    In some embodiments, the elongate shaft includes a lumen therethrough configured for passage of a stylet. In some embodiments, the at least one electrode comprises a plurality of electrodes positioned so as to wrap at least partially around the elongate shaft. And in some embodiments, the elongate shaft is configured for implantation in an arrangement so that the at least one electrode is positioned near a dorsal root ganglion. 
         [0038]    In yet another aspect of the present invention, a lead is provided for stimulating a body tissue, wherein the lead comprises a first elongate structure having a first distal end configured to be positioned near the body tissue and a first proximal end coupleable with a pulse generator. The first elongate structure has a first electrode disposed near the first distal end. The lead also includes a second elongate structure having a second distal end, a second proximal end and a second electrode disposed near the second distal end. The second elongate structure is attached to the first elongate structure in a layered configuration so that stimulation energy is transmittable from the coupled pulse generator to the first and second electrode so as to stimulate the body tissue. 
         [0039]    In some embodiments, the layered configuration offsets the distal ends. In some embodiments, the first and second electrodes are arranged substantially linearly along a longitudinal axis of the distal end. 
         [0040]    In some instances, the lead further comprises a third elongate structure having a third proximal end, a third distal end and a third electrode disposed near the third distal end, wherein the third elongate structure is attached to the second elongate structure in a layered configuration so that stimulation energy is transmittable from the coupled pulse generator to the third electrode so as to stimulate the body tissue. Typically, the distal ends of the layered configuration of elongate structures are passable through a needle. 
         [0041]    In some embodiments, the at least one conductive trace extends from each electrode toward its respective proximal end. In such embodiments, each conductive trace may have a shape so that the layered configuration balances the conductive traces. At least one of the at least one conductive traces may have a zig-zag or serpentine shape. 
         [0042]    Typically, the first elongate structure comprises a dielectric film. In such instances, the first electrode is comprised of a biocompatible conductive metal, alloy or combination of these plated onto the dielectric film. Optionally, the biocompatible conductive metal, alloy or combination includes gold, titanium, tungsten, titanium tungsten, titanium nitride, platinum, iridium or platinum-iridium alloy. 
         [0043]    Other objects and advantages of the present invention will become apparent from the detailed description to follow, together with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1A-1B, 2, 3, 4, 5  illustrate prior art. 
           [0045]      FIG. 6, 6A, 6B  illustrates an embodiment of a flexible circuit lead of the present invention. 
           [0046]      FIGS. 7A, 7B, 7C, 7D  illustrate a variety of approaches to an example target anatomy for positioning the leads of the present invention. 
           [0047]      FIG. 8  illustrates electrodes positioned more proximal to the distal tip of the lead. 
           [0048]      FIG. 9  illustrates a distal end of an embodiment of a flexible circuit lead of the present invention. 
           [0049]      FIG. 10  illustrates a proximal end of an embodiment of a flexible circuit lead of the present invention 
           [0050]      FIGS. 11A-11B  illustrate a layered lead comprising two or more individual leads which are layered and bonded together. 
           [0051]      FIG. 12  illustrates an embodiment of a layered lead in an expanded view. 
           [0052]      FIGS. 13, 13A, 13B  illustrates an example of a lead which may be used in layering. 
           [0053]      FIG. 14  illustrates an example process and fixture for forming a layered lead. 
           [0054]      FIG. 15A  illustrates a lead of the present invention having an oval, rounded or circular distal end. 
           [0055]      FIG. 15B  illustrates the lead of  FIG. 15A  positioned so that its distal end is in proximity to a dorsal root ganglion. 
           [0056]      FIGS. 16A, 16B, 16C  illustrate a distal end of a lead which is curlable or rollable. 
           [0057]      FIG. 17  illustrates a lead of the present invention having a pronged distal end. 
           [0058]      FIG. 18  illustrates the lead of  FIG. 17  positioned so that its distal end is in proximity to a dorsal root ganglion. 
           [0059]      FIGS. 19-20  illustrate an embodiment of a shaped flexible circuit lead which can form a three dimensional shape. 
           [0060]      FIG. 21A-21B  illustrate a delivery device comprises a flattened tube having a distal end and a pair of obturators which are advanceable out of the distal end. 
           [0061]      FIG. 22  illustrates a flexible circuit lead attached to a delivery device. 
           [0062]      FIG. 23  illustrates a flexible circuit lead particularly suited for wrapping around a catheter. 
           [0063]      FIGS. 24-25  illustrate an example connector of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0064]      FIG. 6  illustrates an embodiment of a lead  100  of the present invention. The lead  100  is comprised of a flexible circuit. In particular, the lead  100  is comprised of an elongate structure  107  having a distal end  102  and a proximal end  104 . The distal end  102  is configured to be positioned near a target body tissue and the proximal end  104  is coupleable with a power source or implantable pulse generator (IPG).  FIG. 6A  provides a detailed illustration of the distal end  102  of the lead  100  of  FIG. 6 . As shown, the lead  100  includes at least one electrode  106  plated on the dielectric film. In this embodiment, four electrodes  106  are present in an array. It may be appreciated that any number of electrodes  106  may be used in any desired arrangement, including longitudinally aligned individually (as shown) or in pairs or sets.  FIG. 6B  provides a detailed illustration of the proximal end  104  of the lead  100  of  FIG. 6 . The proximal end  104  includes contact pads  108  that are used to connect with the IPG. In this embodiment, four contact pads  108  are shown, one corresponding to each electrode  106 . Each contact pad  108  is electrically connected with an electrode  106  through a conductive trace  110  that extends therebetween, thus from the proximal end  104  to the distal end  102 . Stimulation energy is transmitted from the IPG through the contact pads  108  and through trace  110  to the electrodes  106  which stimulate the desired target tissue. It may be appreciated that in some embodiments, the conductive traces  110  are arranged so that each contact pad  108  is connected with more than one electrode  106  or each electrode  106  is connected with more than one contact pad  108 . 
         [0065]    The leads  100  of the present invention may be used to stimulate a variety of target tissues, particularly a dorsal root ganglion DRG.  FIGS. 7A-7D  illustrate various approaches to the DRG and positioning a lead  100  of the present invention so as to stimulate the DRG. Embodiments of these approaches include passing through, near or along one or more posterior or lateral openings in the bony structure of the spinal column. An example of a posterior opening is an opening between adjacent spinous processes. An example of a lateral opening is the foramen or opening at least partially defined by the articulating processes and the vertebrae.  FIG. 7A  illustrates a retrograde ( 100   a ), antegrade ( 100   b ) and lateral approach ( 100   c ) to the dorsal root and DRG from the spinal column.  FIG. 7B  illustrates a retrograde ( 100   d ), antegrade ( 100   e ) and lateral approach ( 100   f ) to the dorsal root and DRG from outside of the spinal column, such as from a side or traditional percutaneous approach.  FIG. 7C  illustrates an antegrade approach to a dorsal root and DRG between an articulating process (not shown) and the vertebral body (not shown).  FIG. 7D  illustrates a retrograde approach to a dorsal root and DRG between an articulating process (not shown) and a vertebral body (not shown). The leads of the present invention may also be positioned by any other suitable method or approach. One exemplary retrograde approach is a retrograde translaminar approach. One exemplary approach is an antegrade translaminar approach. One exemplary lateral approach is a transforamenal approach. 
         [0066]    As mentioned above, each lead  100  includes at least one electrode  106 , preferably two, three, four, five, six or more electrodes. The lead  100  is preferably aligned so that at least one of the at least one electrodes  160  is positioned as close to the target location as possible, for example, on the DRG. In some situations, the DRG has a size of 5-10 mm. Thus, in some embodiments, a lead  100  having four 1 mm square electrodes spaced 1-2 mm apart would allow all four of the electrodes to simultaneously contact the DRG. In such an instance, all four electrodes may provide stimulation energy. In other embodiments, the electrodes may be sized or shaped so that less than the total number of electrodes are desirably positioned on or near the target location. This may also occur due to placement of the lead. In such instances, a subset of the electrodes may provide stimulation energy, preferably one or more electrodes positioned closest to the target location. This assists in reducing or eliminating undesired stimulation of non-target anatomies. 
         [0067]    It may be appreciated that the electrodes may be positioned at any location along the length of the lead, may have any suitable shape and any suitable spacing.  FIG. 8  illustrates electrodes  160  positioned more proximal to the distal tip of the lead  100 . Thus, a portion of the lead  100  having no electrodes  160  extends distally beyond the last electrode  160 . When the electrodes  160  are positioned over the target location, the distal most end of the lead  100  extends therefrom, such as transforamenally. Such extension may assist in anchoring the lead. It may be appreciated that the lead  100  of  FIG. 8  may alternatively be positioned by any of the approaches listed above, or any other approaches. 
         [0068]      FIG. 9  illustrates a distal end  102  of another embodiment of a flexible circuit lead  100  of the present invention. In this embodiment, three electrodes  106  are disposed in an array on the film structure  107 , each electrode  106  having a trace  110  which extends toward the proximal end  104  of the lead. In this embodiment, the lead  100  also includes an anchoring feature  118  which assists in anchoring the lead  100  within tissue to resist migration of the lead  100 . In this embodiment, the anchoring feature  118  comprises a plurality of serrations or notches  120  cut into the film structure  107 . The notches  120  may have any suitable shape, dimension or spacing. Likewise, the notches  120  may be symmetrical, non-symmetrical, present along one edge  111  of the film structure  107  or along more than one edge. In this embodiment, the anchoring feature  118  extends distally of the distal-most electrode  106 , however it may disposed at any location along the lead  100 . 
         [0069]      FIG. 10  illustrates an example of a proximal end of the lead  100  corresponding to the distal end  102  of  FIG. 9 . Here, each of the three traces  110  terminate in a contact pad  108 . Each contact pad  108  is then electrically connected with a connection terminal (as will be described in a later section) which transmits stimulation energy from the implanted IPG. 
         [0070]    The thinness and flexibility of the dielectric film allow a variety of different types of leads  100  to be formed. Such types include layered leads, circular leads, leads which curl or wrap around target tissue, leads which fold and expand, leads which surround a target tissue, leads mounted on delivery devices and a variety of other leads designs suitable for stimulating specific types of target tissue, particularly a DRG. 
         [0071]      FIGS. 11A-11B  illustrate an embodiment of a layered lead  130 . A layered lead  130  comprises two or more individual leads which are layered and bonded together.  FIG. 11A  shows three individual leads  100   a ,  100   b ,  100   c , each comprising a film structure  107  having an electrode  106  disposed thereon and a trace  110 . It may be appreciated that each individual lead may alternatively have a plurality of electrodes disposed thereon, such as in an array. The three leads  100   a ,  100   b ,  100   c  are staggered so that the electrodes  106  are exposed and facing the same direction. In this embodiment, the traces  110  are positioned so that when the leads are layered, the traces  110  are balanced across the layered lead  130 . For example, the traces  110  may have opposing zig-zag or serpentine shapes when layered. This improves flexibility and handling characteristics of the lead  130 .  FIG. 11B  provides a side-view of the layered lead  130  of  FIG. 11A . Such layering allows each individual lead more surface area, such as for redundant traces  110  for each electrode  106 . Since the leads are so thin, layering of the leads is still very thin and flexible. In addition, insulation layers may be bonded between one or more of the individual leads. In some embodiments, the proximal end of the layered lead is layered in a mirrored fashion so that each of the contact pads are exposed. 
         [0072]      FIG. 12  illustrates an embodiment of a layered lead  130  in an expanded view. The three leads  100   a ,  100   b ,  100   c  are staggered so that the electrodes  106  are exposed and facing the same direction. In this embodiment, the contact pads  108  are disposed on an opposite side of each of the leads  100   a ,  100   b ,  100   c . This provides for the contact pads  108  to also be exposed and facing the same direction when the leads are layered. 
         [0073]      FIG. 13  illustrates an example of a lead, such as lead  100   a , which may be used in layering. The lead  100   a  comprises an elongate film structure  107  having a distal end  102  and a proximal end  104 .  FIG. 13A  provides a detailed illustration of the distal end  102  of the lead  100  of  FIG. 13 . As shown, the lead  100   a  includes at least one electrode  106  plated on the “A-side” of the dielectric film structure  107 . In this embodiment, one electrode is present  FIG. 13B  provides a detailed illustration of the proximal end  104  of the lead  100   a  of  FIG. 13 . The proximal end  104  includes a contact pad  108  on the “B-side” of the film structure  107  which is used to connect with the IPG. In this embodiment, a circuit trace  110  extends from the electrode  106 , along the “A-side” of the structure  107 , through a via to the “B-side” of the structure  107  and connects with the contact pad  108 . Thus, when a plurality of such leads are layered, as in  FIG. 12 , stimulation energy may be transmitted from each of the staggered contact pads  108 , through the associated traces, to the associated staggered electrodes  106  to stimulate the desired target tissue. 
         [0074]      FIG. 14  illustrates an example process and fixture for forming a layered lead  130 . Three individual leads  100   a ,  100   b ,  100   c  are shown, each comprising a film structure  107  having an electrode  106  disposed thereon and a trace  110 . In this embodiment, each lead  100   a ,  100   b ,  100   c  is of the same length, however differing sized portions are shown for clarity. In addition, each lead  100   a ,  100   b ,  100   c  has an alignment hole  132 . The alignment holes  132  are used to assist in consistently and precisely aligning the leads in a layered arrangement. A fixture  134  is shown having one or more posts  136  positioned thereon. The posts  136  are sized and arranged so that the posts  136  are passable through the alignment holes  132  when the leads  100   a ,  100   b ,  100   c  are placed thereon. Once the leads  100   a ,  100   b ,  100   c  are desirably positioned, the leads are bonded and fixed in this arrangement. The layered lead  130  may then be removed from the fixture  134 . In some embodiments, the resulting alignment holes  132  may be used for other purposes, such as for suturing a portion of the layered lead  130  to tissue during implantation. 
         [0075]    It may be appreciated that the flexible circuit leads  100  may have a variety of shapes, sizes and dimensions. In particular, the distal end  102  may be shaped to provide a particular electrode placement or to conform to a particular anatomy. For example,  FIG. 15A  illustrates a lead  100  of the present invention having an oval, rounded or circular distal end  102 . Here, the film structure  107  is formed into the oval, rounded or circular shape and the electrodes  106  are arranged therearound, such as in a circular or arc pattern. This arrangement may provide a particularly desirable stimulation area or may more easily target a particular tissue, such as a dorsal root ganglion DRG which may have a circular or oval shape.  FIG. 15B  illustrates the lead  100  of  FIG. 15A  positioned so that its distal end  102  is in proximity to a DRG. As shown, the distal end  102  is positioned over the DRG so that its circular shape substantially aligns with the circular shape of the DRG. The lead  100  is positioned so that the electrodes  106  face the DRG, and are therefore represented in dashed line. Appropriate electrodes may then be selected for stimulation of the DRG based on desired pain relief. In some instances, the circular shape increases the number of electrodes  106  able to be used for stimulation and promotes selective stimulation of the DRG. 
         [0076]    In addition, the film structure  107  may be curled or rolled for ease of delivery and/or to wrap around a target tissue area.  FIG. 16A  illustrates the distal end  102  rolled into a cylindrical shape. Such a cylindrical shape may easily fit within a cylindrically shaped delivery catheter or device. Thus, the lead  100  may be advanced from the delivery device in a rolled orientation wherein it may be deployed to an at least partially unrolled state.  FIG. 16B  illustrates the distal end  102  partially unrolled and  FIG. 16C  illustrates the distal end  120  in an unrolled, flat orientation. In an at least partially unrolled state, the distal end  102  may fully or partially wrap around a target tissue (such as the DRG or including the DRG). In this configuration, the electrodes face each other having the target tissue therebetween. Appropriate electrodes may then be selected for stimulation of the tissue area therebetween based on patient interview for best relief of pain. In some embodiments, one or more obturators may be used to assist in unrolling and positioning of the circular lead  100 . 
         [0077]      FIG. 17  illustrates a lead  100  of the present invention having a pronged distal end  102 . Here, the film structure  107  is shaped to provide a plurality of elongate prongs  140 , each prong  140  having an electrode  106  positioned thereon. The prongs  140  may wrap around a delivery catheter or around a portion of the anatomy during implantation. For example,  FIG. 18  illustrates the lead  100  of  FIG. 17  positioned so that its distal end  102  is in proximity to a DRG. As shown, the distal end  102  is positioned over the DRG and at least some of the prongs  140  wrap around the DRG. The lead  100  is positioned so that the electrodes  106  face the DRG, and are therefore represented in dashed line. Appropriate electrodes may then be selected for stimulation of the DRG based on desired pain relief. In some instances, the pronged shape increases the number of electrodes  106  able to be used for stimulation and promotes selective stimulation of the DRG. 
         [0078]    It may be appreciated that the film structure  107  is not only bendable and flexible, but also foldable and creasable. Thus, the leads  100  can form a variety of three-dimensional shapes which assist in wrapping around particular tissues and anatomies.  FIGS. 19-20  illustrate an embodiment of a shaped flexible circuit lead  500  of the present invention. The shaped lead  500  is comprised of two individual leads  100   a ,  100   b , each having at least one electrode  106  along one side of its distal end  102  and at least one corresponding contact pad  108  along the opposite side of its proximal end  104 . Thus, the electrodes  106  and the contact pads  108  reside on opposite sides of each individual lead  100   a ,  100   b . Lead  100   a  is folded to form a crease  502   a  along its length between the electrodes  106  and the contact pads  108  so that an acute angle α is formed between the back of the distal end (opposite the electrodes  106 ) and the face of the proximal end  104  having the contact pads  108  thereon. Likewise, lead  100   b  is folded to form a crease  502   b  along its length between the electrodes  106  and the contact pads  108  so that an acute angle β is formed between the back of the distal end (opposite the electrodes  106 ) and the face of the proximal end  104  having the contact pads  108  thereon. The angles α, β may be the same or different. The leads  100   a ,  100   b  are assembled so that the creases  502   a ,  502   b  are aligned and the angles α, β face away from each other, as shown. Consequently, the distal ends of the leads  100   a ,  100   b  form a V shape wherein the electrodes  106  face each other within the mouth of the V. The leads  100   a ,  100   b  may optionally be bonded together to maintain this shaped lead  500 . Alternatively, the leads  100   a ,  100   b  may reside in this arrangement, allowing the leads to slide in relation to each other to adjust position. 
         [0079]      FIG. 20  illustrates the shaped lead  500  wrapped around a target tissue area, including a target DRG. As shown, the lead  500  is positioned so the target tissue area resides between at least a portion of the electrodes  106  along the mouth of the V. Thus, stimulation energy E provided by the electrodes  106 , is provided to the tissue area laying therebetween (within the V). This provides a higher likelihood of stimulating the target DRG, since the exact location of the DRG within the target tissue area may not be known. 
         [0080]    Positioning of the contact pads  108  on opposite sides of the assembled shaped lead  500  allows the joined proximal end  104  to easily be connected to a connector (such as in a quick connect arrangement) which is in turn connected with an IPG to supply the stimulation energy E. 
         [0081]    It may be appreciated that other shapes may be formed, such as a “J” shape. Or, a triangular shaped lead may be formed having three distal end portions (forming a tripod shape). When deployed, this may covering a larger target tissue area than the V or J shapes. 
         [0082]    Likewise, the shapes may be formed by differing arrangements of individual leads or portions of leads. For example, the above described “V” shape may be formed by a longer flex circuit lead which is creased and a smaller flex circuit bonded at the crease to form the construct with an interconnect at the crease. 
         [0083]    Delivery of the above described shaped lead  500  can be accomplished by a variety of methods. For example, the lead  500  may be delivered with the use of a delivery device such as illustrated in  FIGS. 21A-21B . In this embodiment, the delivery device  520  comprises a flattened tube  522  having a distal end  524  and a pair of obturators  526   a ,  526   b  which are advanceable out of the distal end  524 . The obturators  526   a ,  526   b  are each comprised of a preformed spring metal or memory metal which is able to curve or bend to form an angle (such as angle α or angle β) in relation to the flattened tube  522 . 
         [0084]      FIG. 21A  illustrates a first obturator  526   a  extending from the distal end  524  of the tube  522 . One of the individual flex circuit leads  100   a  is attached to the obturator  526   a , such as with the use of a hook  528  which holds the lead  100   a  in place near the distal tip of the obturator  526   a  during deployment. The obturator  526   a  bluntly dissects tissue as it is advanced, drawing the lead  100   a  into the dissected tissue.  FIG. 21B  illustrates a second obturator  526   b  extending from the distal end  524  of the tube  522 . Another individual flex circuit lead  100   b  is attached to the obturator  526   b , such as with the use of a hook  528 . This obturator  526   b  bluntly dissects tissue on the opposite side of the target so that the target lies near or within the “V” of the obturators  526   a , 526   b  (and therefore between the electrodes  106  of the leads  100   a ,  100   b ) 
         [0085]    Once deployed, the leads  100   a ,  100   b  are released from the hooks  528  and the obturators  526   a ,  526   b  are retracted into the tube  522 , leaving the leads  100   a ,  100   b  behind implanted in a “V” shaped configuration. Appropriate electrode pairs may then be selected for stimulation of the tissue area therebetween based on patient interview for best relief of pain (in the case of DRG stimulation). 
         [0086]    The flexible circuit leads  100  of the present invention are particularly suitable for implantation in areas of the human body which benefit from highly thin and flexible leads. However, in some portions of the anatomy, delivery of such thin and flexible leads may be challenging due to tortuous or constrained delivery paths. Therefore, the flexible circuit leads  100  may be attached to a delivery device, such as a delivery catheter  140 , as illustrated in  FIG. 22 . The delivery catheter  140  comprises an elongate shaft  142  having a lumen  144  therethrough for passage of a stylet. Thus, the catheter  140  may be comprised of a flexible polymer material to retain the desirable flexibility of the lead  100  yet provide sufficient rigidity for deliverability. In some embodiments, the delivery catheter  140  remains in place with the flexible circuit lead thereattached wherein both remain implanted. In such embodiments, the flexible circuit lead  100  may wrap around the catheter  140  so as to provide electrodes  106  on various surfaces of the catheter  140 .  FIG. 23  illustrates a flexible circuit lead  100  particularly suited for wrapping around a catheter  140 . Here, the electrodes  106  are aligned in a lateral row so that the electrodes  106  will wrap around the circumference of the delivery catheter  140  when mounted thereon. It may be appreciated that any of the flexible leads  100  described herein may be mounted on or attached to a delivery device. 
         [0087]    The leads of the present invention are typically passable through a 16 gauge needle, 17 gauge needle, 18 gauge needle or a smaller needle. In some embodiments, the electrode(s) of the present invention have a less than 3 mm square area, preferably less than 2 mm square area. In some embodiments, the electrodes have an approximately 0.6-1 mm square area. 
         [0088]    Such reduced dimensions in electrode area and overall size (e.g. outer diameter) are possible due to the increased specificity of the stimulation energy. By positioning at least one of the electrodes on, near or about the desired target tissue, such as the dorsal root ganglion, the stimulation energy is supplied directly to the target anatomy (i.e. the DRG). Thus, a lower power may be used than with a leads which is positioned at a greater distance from the target anatomy. For example, the peak power output of the leads of the present invention are typically in the range of approximately 20 μW-0.5 mW. Such reduction in power requirement for the leads of the present invention may in turn eliminate the need to recharge the power source in the implanted pulse generator (IPG). Moreover, the proximity to the stimulation site also reduce the total amount of energy required to produce an action potential, thus decreasing the time-averaged power significantly and extending battery life. 
         [0089]    As described previously, the proximal end  104  of each lead  100  is joinable with an IPG to supply stimulation energy to the electrodes  106 .  FIGS. 24-25  illustrate an example proximal end  104  joined with a connector  150  or portion of an IPG. As shown, the proximal end  104  includes one or more contact pads  108  which are electrically connectable to the connector  150  via one or more pins  152 . As shown in cross-section in  FIG. 24 , the connector  150  is able to make multiple connections with the flexible circuit lead  100 . The contact pads  108  are placed over pins  152  that serve as both a means of locating the flexible circuit lead  100  and making the connection with the conductive material of the contact pads  108 . Once the proximal end  104  of the lead  100  is placed over the pins  152  a cover  154  is snapped into place, as shown in  FIG. 25 . The act of snapping the cover  154  on the pins  152  makes the electrical connection between the contact pads  108  and the IPG and can connect many contact pads  108  with just one connection action. 
         [0090]    The connector cover  154  snaps in place with a predictable and significant force, enough to maintain the connection. The pins  152  are spring loaded to maintain the correct connection force. The springs may be comprised of a flexible polymer, such as polyurethane or silicone, or a metal. The springs may be separate or built into the pins  152  that make the connection via MEMS or Wire EDM. 
         [0091]    It may be appreciated that this connector  150  may be used for any multiple lead connection that benefits from a simplified means for connection. Such application may be for use with a medical device or any electronics connections. 
         [0092]    Although the foregoing Invention has been described in some detail by way of illustration and example, for purposes of clarity of understanding, it will be obvious that various alternatives, modifications and equivalents may be used and the above description should not be taken as limiting in scope of the invention.