Abstract:
An insertion kit for percutaneously implanting an electrical stimulating paddle lead into a patient includes a paddle lead introducer. The paddle lead introducer facilitates percutaneous implantation of a paddle lead into the patient. The paddle lead introducer includes a sheath and a dilator. The sheath is insertable into the patient. The sheath is configured and arranged to receive a paddle lead during implantation of the paddle lead into the patient. The sheath can divide into at least two parts for removal of the sheath from the paddle lead upon implantation of the paddle lead. The dilator is insertable into the sheath. A first end of the dilator defines an aperture at a tip of the first end. The first end of the dilator has a transverse circumference that increases from the tip towards a second end.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/443,358 filed on Feb. 16, 2011, which is incorporated herein by reference. 
     
    
     FIELD 
       [0002]    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 lead introducers for facilitating percutaneous implantation of implantable electrical stimulation paddle leads, as well as methods of making and using the introducers, paddle leads, and electrical stimulation systems. 
       BACKGROUND 
       [0003]    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. 
         [0004]    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. 
       BRIEF SUMMARY 
       [0005]    In one embodiment, an insertion kit for percutaneously implanting an electrical stimulating paddle lead into a patient includes a paddle lead introducer. The paddle lead introducer is configured and arranged for facilitating percutaneous implantation of a paddle lead into the patient. The paddle lead introducer includes a sheath and a dilator. The sheath is insertable into the patient. The sheath has a first end, an opposing second end, and a longitudinal length. The sheath is configured and arranged to receive a paddle lead during implantation of the paddle lead into the patient. The sheath is configured and arranged to divide into at least two parts for removal of the sheath from the paddle lead upon implantation of the paddle lead into the patient. The dilator is insertable into the sheath. The dilator has a first end, an opposing second end, and a longitudinal length. The first end of the dilator defines an aperture at a tip of the first end. The first end of the dilator has a transverse circumference that increases from the tip towards the second end. 
         [0006]    In another embodiment, a method for percutaneously implanting an electrical stimulation paddle lead into a patient includes providing an insertion kit. The insertion kit includes a paddle lead introducer. The paddle lead introducer is configured and arranged for facilitating percutaneous implantation of a paddle lead into the patient. The paddle lead introducer includes a sheath and a dilator. The sheath is insertable into the patient. The sheath has a first end, an opposing second end, and a longitudinal length. The sheath is configured and arranged to receive a paddle lead during implantation of the paddle lead into the patient. The sheath is configured and arranged to divide into at least two parts for removal of the sheath from the paddle lead upon implantation of the paddle lead into the patient. The dilator is insertable into the sheath. The dilator has a first end, an opposing second end, and a longitudinal length. The first end of the dilator defines an aperture at a tip of the first end. The first end of the dilator has a transverse circumference that increases from the tip towards the second end. The dilator of the insertion kit is inserted into the sheath such that the first end of the dilator extends axially from the first end of the sheath. An epidural needle is inserted into the dilator such that a first end of the epidural needle extends axially from the first end of the dilator. The sheath, dilator, and epidural needle are guided to a target stimulation location within the patient. The epidural needle and dilator are removed, leaving the sheath in the patient. The paddle lead is inserted into the sheath and guided to the target stimulation location. The paddle lead includes a paddle body having a first major surface, an opposing second major surface, a longitudinal length, and at least one lead body. Each of the at least one lead bodies has a proximal end and a distal end. The distal end of the at least one lead body is coupled to the paddle body. A plurality of electrodes are disposed on the first major surface of the paddle body. A plurality of terminals are disposed at the proximal ends of each of the at least one lead bodies. A plurality of conductive wires couple the plurality of electrodes electrically to the plurality of terminals. The sheath is removed from the paddle lead, leaving the paddle lead implanted in the patient. 
         [0007]    In yet another embodiment, a method for percutaneously implanting an electrical stimulation paddle lead into a patient includes providing an insertion kit. The insertion kit includes a paddle lead introducer. The paddle lead introducer is configured and arranged for facilitating percutaneous implantation of a paddle lead into the patient. The paddle lead introducer includes a sheath and a dilator. The sheath is insertable into the patient. The sheath has a first end, an opposing second end, and a longitudinal length. The sheath is configured and arranged to receive a paddle lead during implantation of the paddle lead into the patient. The sheath is configured and arranged to divide into at least two parts for removal of the sheath from the paddle lead upon implantation of the paddle lead into the patient. The dilator is insertable into the sheath. The dilator has a first end, an opposing second end, and a longitudinal length. The first end of the dilator defines an aperture at a tip of the first end. The first end of the dilator has a transverse circumference that increases from the tip towards the second end. The dilator of the insertion kit is inserted into the sheath such that the first end of the dilator extends axially from the first end of the sheath. An epidural needle is inserted into the patient and guided to the target stimulation location. A lead blank is inserted into the epidural needle. The epidural needle is removed, leaving the lead blank in the patient. The sheath and the dilator of the insertion kit are disposed over the lead blank. The dilator and lead blank are removed, leaving the sheath in the patient. The paddle lead is inserted into the sheath and guided to the target stimulation location. The paddle lead includes a paddle body having a first major surface, an opposing second major surface, a longitudinal length, and at least one lead body. Each of the at least one lead bodies has a proximal end and a distal end. The distal end of the at least one lead body is coupled to the paddle body. A plurality of electrodes are disposed on the first major surface of the paddle body. A plurality of terminals are disposed at the proximal ends of each of the at least one lead bodies. A plurality of conductive wires couple the plurality of electrodes electrically to the plurality of terminals. The sheath is removed from the paddle lead, leaving the paddle lead implanted in the patient. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following drawings. In the drawings, like reference numerals refer to like parts throughout the various figures unless otherwise specified. 
           [0009]    For a better understanding of the present invention, reference will be made to the following Detailed Description, which is to be read in association with the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a schematic view of one embodiment of an electrical stimulation system that includes a paddle body coupled to a control module via lead bodies, according to the invention; 
           [0011]      FIG. 2A  is a schematic side view of one embodiment of a plurality of connector assemblies disposed in the control module of  FIG. 1 , the connector assemblies configured and arranged to receive the proximal portions of the lead bodies of  FIG. 1 , according to the invention; 
           [0012]      FIG. 2B  is a schematic side view of one embodiment of a proximal portion of a lead body and a lead extension coupled to a control module, the lead extension configured and arranged to couple the proximal portion of the lead body to the control module, according to the invention; 
           [0013]      FIG. 2C  is a schematic side view of one embodiment of a connector assembly disposed in the control module of  FIG. 2B , the connector assembly configured and arranged to receive the lead extension of  FIG. 2B , according to the invention; 
           [0014]      FIG. 3  is a schematic longitudinal cross-sectional view of one embodiment of one of the connector assemblies of  FIG. 1 , according to the invention. 
           [0015]      FIG. 4  is a schematic perspective view a control module with a header that defines four ports, according to the invention; 
           [0016]      FIG. 5A  is a schematic perspective view of one embodiment of a lead introducer suitable for percutaneous implantation of a paddle lead into a patient, the introducer including a sheath and a dilator, according to the invention; 
           [0017]      FIG. 5B  is a schematic perspective view of one embodiment of a lead blank inserted into an epidural needle which, in turn, is inserted into the lead introducer of  FIG. 5A , according to the invention; 
           [0018]      FIG. 6  is a schematic top view of one embodiment of the paddle body of  FIG. 1  and the lead blank of  FIG. 5B , the paddle body defining an aperture configured and arranged to receive the lead blank, according to the invention; 
           [0019]      FIG. 7  is a schematic perspective view of one embodiment of the paddle body of  FIG. 1  partially disposed in the sheath of  FIG. 5A , according to the invention; 
           [0020]      FIG. 8  is a schematic perspective view of one embodiment of the sheath of  FIG. 5A  being removed from the paddle body of  FIG. 1 , according to the invention; and 
           [0021]      FIG. 9  is a schematic overview of one embodiment of components of a stimulation system, including an electronic subassembly disposed within a control module, according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    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 lead introducers for facilitating percutaneous implantation of implantable electrical stimulation paddle leads, as well as methods of making and using the introducers, paddle leads, and electrical stimulation systems. 
         [0023]    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, 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; and 6,741,892; 7,244,150; 7,672,734; 7,761,165; 7,949,395; and 7,974,706; and U.S. Patent Applications Publication Nos. 2005/0165465, 2007/0150036; 2007/0219595; and 2008/0071320, all of which are incorporated by reference. 
         [0024]      FIG. 1  illustrates schematically one embodiment of an electrical stimulation system  100 . The electrical stimulation system includes a control module (e.g., a stimulator or pulse generator)  102 , a paddle body  104 , and one or more lead bodies  106  coupling the control module  102  to the paddle body  104 . The paddle body  104  and the one or more lead bodies  106  collectively form a paddle lead  107 . The paddle body  104  typically includes a plurality of electrodes  134  that form an array of electrodes  133 . The control module  102  typically includes an electronic subassembly  110  and an optional power source  120  disposed in a sealed housing  114 . In  FIG. 1 , two lead bodies  106  are shown coupled to the control module  102 . 
         [0025]    The control module  102  typically includes one or more connector assemblies  144  into which the proximal end of the one or more lead bodies  106  can be plugged to make an electrical connection via connector contacts (e.g.,  216  in  FIG. 2A ). The connector contacts are coupled to the electronic subassembly  110  and the terminals are coupled to the electrodes  134 . In  FIG. 1 , two connector assemblies  144  are shown. 
         [0026]    The one or more connector assemblies  144  may be disposed in a header  150 . The header  150  provides a protective covering over the one or more connector assemblies  144 . The header  150  may be formed using any suitable process including, for example, casting, molding (including injection molding), and the like. In addition, one or more lead extensions  224  (see  FIG. 2B ) can be disposed between the one or more lead bodies  106  and the control module  102  to extend the distance between the one or more lead bodies  106  and the control module  102 . 
         [0027]    The electrical stimulation system or components of the electrical stimulation system, including one or more of the lead bodies  106 , the paddle body  104 , and the control module  102 , 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. 
         [0028]    The electrodes  134  can 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 electrodes  134  are formed from one or more of: platinum, platinum iridium, palladium, titanium nitride, or rhenium. 
         [0029]    The number of electrodes  134  in the array of electrodes  133  may vary. For example, there can be two, three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen, or more electrodes  134 . As will be recognized, other numbers of electrodes  134  may also be used. In  FIG. 1 , sixteen electrodes  134  are shown. The electrodes  134  can be formed in any suitable shape including, for example, round, oval, triangular, rectangular, pentagonal, hexagonal, heptagonal, octagonal, or the like. 
         [0030]    The electrodes of the paddle body  104  or one or more lead bodies  106  are typically disposed in, or separated by, a non-conductive, biocompatible material including, for example, silicone, polyurethane, and the like or combinations thereof. The paddle body  104  and one or more lead bodies  106  may 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 material typically extends from the distal end of the lead body to the proximal end of each of the one or more lead bodies  106 . The non-conductive, biocompatible material of the paddle body  104  and the one or more lead bodies  106  may be the same or different. The paddle body  104  and the one or more lead bodies  106  may be a unitary structure or can be formed as two separate structures that are permanently or detachably coupled together. 
         [0031]    Terminals (e.g.,  210  in  FIG. 2A ) are typically disposed at the proximal end of the one or more lead bodies  106  for connection to corresponding conductive contacts (e.g.,  216  in  FIG. 2A ) in connector assemblies disposed on, for example, the control module  102  (or to other devices, such as conductive contacts on a lead extension, an operating room cable, a lead splitter, a lead adaptor, or the like). Conductive wires (not shown) extend from the terminals to the electrodes  134 . Typically, one or more electrodes  134  are electrically coupled to a terminal (e.g.,  210  in  FIG. 2A ). In some embodiments, each terminal (e.g.,  210  in  FIG. 2A ) is only coupled to one electrode  134 . 
         [0032]    The conductive wires may be embedded in the non-conductive material of the paddle lead or can be disposed in one or more lumens (not shown) extending along the paddle 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 paddle lead, for example, for inserting a stylet rod to facilitate placement of the paddle 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 paddle lead, for example, for infusion of drugs or medication into the site of implantation of the paddle body  104 . 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. 
         [0033]    As discussed above, the one or more lead bodies  106  may be coupled to the one or more connector assemblies  144  disposed on the control module  102 . The control module  102  can include any suitable number of connector assemblies  144  including, for example, two three, four, five, six, seven, eight, or more connector assemblies  144 . It will be understood that other numbers of connector assemblies  144  may be used instead. In  FIG. 1 , each of the two lead bodies  106  includes eight terminals that are shown coupled with eight conductive contacts disposed in a different one of two different connector assemblies  144 . 
         [0034]      FIG. 2A  is a schematic side view of one embodiment of the two lead bodies  106  shown in  FIG. 1  configured and arranged for coupling with the control module  102 . A plurality of connector assemblies  144  are disposed in the control module  102 . In at least some embodiments, the control module  102  includes two, three, four, or more connector assemblies  144 . Typically, the number of connector assemblies  144  disposed in the control module  102  is equal to the number of lead bodies  106  of the paddle lead. For example, in  FIG. 2A , the two lead bodies  106  shown in  FIG. 1  are shown configured and arranged for insertion into two connector assemblies  144  disposed on the control module  102 . 
         [0035]    The connector assemblies  144  each include a connector housing  214  and a plurality of connector contacts  316  disposed therein. Typically, the connector housing  214  defines a port (not shown) that provides access to the plurality of connector contacts  216 . In at least some embodiments, the connector assemblies  144  further include retaining elements  218  configured and arranged to fasten the corresponding lead bodies  206  to the connector assemblies  144  when the lead bodies  106  are inserted into the connector assemblies  144  to prevent undesired detachment of the lead bodies  106  from the connector assemblies  144 . For example, the retaining elements  218  may include apertures through which fasteners (e.g., set screws, pins, or the like) may be inserted and secured against an inserted lead body (or lead extension). 
         [0036]    In  FIG. 2A , the plurality of connector assemblies  144  are disposed in the header  150 . In at least some embodiments, the header  150  defines one or more ports  204  into which a proximal end  206  of the one or more lead bodies  106  with terminals  210  can be inserted, as shown by directional arrows  212 , in order to gain access to the connector contacts  216  disposed in the connector assemblies  144 . 
         [0037]    When the lead bodies  106  are inserted into the ports  204 , the connector contacts  216  can be aligned with the terminals  210  disposed on the lead bodies  106  to electrically couple the control module  102  to the electrodes ( 134  of  FIG. 1 ) disposed at a distal end of the lead bodies  106 . Examples of connector assemblies in control modules are found in, for example, U.S. Pat. No. 7,244,150 and U.S. Patent Application Publication No. 2008/0071320, which are incorporated by reference. 
         [0038]    In some instances, the electrical stimulation system may include one or more lead extensions.  FIG. 2B  is a schematic side view of one embodiment of a proximal end of a single lead body  106 ′ configured and arranged to couple with a lead extension  224  that is coupled with the control module  102 ′. In  FIG. 2B , a lead extension connector assembly  222  is disposed at a distal end  226  of the lead extension  224 . The lead extension connector assembly  222  includes a contact housing  228 . The contact housing  228  defines at least one port  230  into which a proximal end  206  of the lead body  106 ′ with terminals  210  can be inserted, as shown by directional arrow  238 . The lead extension connector assembly  222  also includes a plurality of connector contacts  240 . When the lead body  106 ′ is inserted into the port  230 , the connector contacts  240  disposed in the contact housing  228  can be aligned with the terminals  210  on the lead body  106  to electrically couple the lead extension  224  to electrodes (not shown) disposed on the lead body  106 ′. 
         [0039]    The proximal end of a lead extension can be similarly configured and arranged as a proximal end of a lead body, such as one of the lead bodies  106 , or the lead body  106 ′. The lead extension  224  may include a plurality of conductive wires (not shown) that electrically couple the connector contacts  240  to terminals at the proximal end  248  of the lead extension  224 . The conductive wires disposed in the lead extension  224  can be electrically coupled to a plurality of terminals (not shown) disposed on the proximal end  248  of the lead extension  224 . 
         [0040]      FIG. 2C  is a schematic side view of one embodiment of the lead extension  224  configured and arranged for coupling with the control module  102 ′. The control module  102 ′ includes a single connector assembly  144 . Alternately, the control module  102 ′ may receive the lead body  106 ′ directly. It will be understood that the control modules  102  and  102 ′ can both receive either lead bodies or lead extensions. It will also be understood that the electrical stimulation system  100  can include a plurality of lead extensions  224 . For example, each of the lead bodies  106  shown in  FIGS. 1 and 2A  can, alternatively, be coupled to a different lead extension  224  which, in turn, are each coupled to different ports of a two-port control module, such as the control module  102  of  FIGS. 1 and 2A . 
         [0041]      FIG. 3  is a schematic longitudinal cross-sectional view of one embodiment of one of the connector assemblies  144 . The connector assembly  144  includes the connector housing  314  into which a lead body or lead extension can be inserted via a port  302  at a distal end  304  of the connector housing  314 . In at least some embodiments, a retaining element  318  is coupled to the connector housing  314 . The retaining element  318  defines an aperture  306  through which a fastener (e.g., a set screw, pin, or the like) may be inserted and secured against a lead body or lead extension when the lead body or lead extension is inserted into the port  302 . Connector contacts, such as the connector contact  216 , are disposed in the connector housing  314 . In at least some embodiments, each of the connector assemblies  144  includes eight connector contacts. 
         [0042]    The connector contacts  216  may be separated from one another by one or more non-conductive spacers (or seals), such as spacer  308 , to prevent electrical contact between adjacent connector contacts  216 . As discussed above, when a proximal end of a lead body or lead extension is inserted into the port  302 , terminals disposed on the inserted lead body or lead extension align with the connector contacts  216 , thereby establishing an electrical connection between the electronic subassembly  110  of the control module  102  and the electrodes  134  of the paddle body. 
         [0043]      FIG. 4  is a schematic perspective view of a control module  102 ″. The header  150  of the control module  102 ″ defines four header ports  404 . Collectively, the header ports  404  are configured and arranged to each receive one or more lead bodies  106  or one or more lead extensions (e.g., lead extension  224  of  FIG. 2B ), or both. The header  150  can define any suitable number of header ports  404  including, for example, one, two, three, four, five, six, seven, eight, or more header ports  404 . In  FIG. 4 , the header  150  is shown defining four header ports  404 . Thus, in at least some embodiments, the control module  102 ″ of  FIG. 4  is configured and arranged to receive up to four lead bodies  106  or lead extensions  224 , or a combination of both. 
         [0044]    The header ports  404  can be defined in the header  150  in any suitable arrangement. In preferred embodiments, each of the header ports  404  are configured and arranged to align with one of the ports  302  of the one or more connector assemblies  144  disposed in the header  150 . For example, in at least some embodiments, four connector assemblies  144  are disposed in the header  150  such that four header ports  404  defined in the header  150  align with the four ports  302  of the four connector assemblies  144 . In at least some embodiments, the number of header ports  404  is no greater than the number of connector assemblies  144 . In at least some embodiments, the number of header ports  404  is no less than the number of connector assemblies  144 . In at least some embodiments, the number of header ports  404  is equal to the number of connector assemblies  144 . 
         [0045]    Conventional paddle leads are typically implanted in a patient using a laminectomy. Laminectomies are invasive procedures. Additionally, laminectomies can be expensive and time-consuming. Moreover, in many regions laminectomies are only performable by neurosurgeons, thereby potentially making the procedure more difficult to schedule. 
         [0046]    As herein described, a percutaneous paddle lead introducer (“introducer”) enables percutaneous implantation of a paddle lead into a patient. It may be advantageous to be able to implant paddle leads percutaneously in lieu of performing a laminectomy. Percutaneous implantations may be less invasive. Additionally, percutaneous implantations may be less expensive and may be performed by either neurosurgeons or anesthesiologists. 
         [0047]    The disclosed introducer includes a sheath at least partially disposed around a dilator. An epidural needle can be inserted into the dilator and used to initiate a path through patient tissue to a target implantation location (e.g., within the epidural space of the patient). The dilator can then be used to push apart enough patient tissue to enable the sheath to move along the path formed by the epidural needle to the target stimulation location. Once the sheath is at the target stimulation location, the paddle lead can be inserted into the sheath, guided to the target stimulation location, and implanted. 
         [0048]      FIG. 5A  is a schematic perspective view of one embodiment of an introducer  502  suitable for percutaneous implantation of a paddle lead into a patient. The introducer  502  includes a sheath  504  and a dilator  506 . The sheath  504  is generally cylindrical with a first end  510 , an opposing second end  512 , and a longitudinal length  514 . The sheath  504  defines a lumen that is configured and arranged to receive the dilator  506  during insertion of the introducer  502 , and that is also configured and arranged to receive the paddle body ( 104  in  FIG. 1 ) during implantation of the paddle body. In at least some embodiments, the sheath  504  is configured and arranged to receive the paddle body without bending the paddle body. The sheath  504  can have any suitable transverse cross-sectional shape including, for example, oval, round, rectangular, or the like. In at least some embodiments, the sheath  504  has at least one transverse axis that is no smaller than a width of the paddle lead ( 104  of  FIG. 1 ). 
         [0049]    The sheath  504  can, optionally, include one or more scored or perforated lines  516  extending along the length  514  of the sheath  504 . The sheath  504  can, optionally, include tabs  518   a,    518   b  disposed at the second end  512  of the sheath  504 . As discussed in further detail below with respect to  FIG. 8  (and as shown in  FIG. 8 ), in at least some embodiments once the paddle lead ( 104  in  FIG. 1 ) is positioned at the target stimulation location, the sheath  504  can be removed from the paddle lead by separating the tabs  518   a,    518   b  from one another, thereby causing the sheath  504  to separate along the scored or perforated lines  516  into two or more pieces that can then be removed from the patient. 
         [0050]    The dilator  506 , likewise, is generally cylindrical with a first end  520 , an opposing second end  522 , and a longitudinal length  524 . The first end  520  of the dilator  506  defines an aperture  530  at a tip of the first end  520  and has a transverse circumference that expands axially from the tip toward the second end  522  (i.e., the first end  520  is funnel-shaped). The dilator  506  can have any suitable transverse cross-sectional shape including, for example, oval, round, rectangular, or the like. 
         [0051]    The sheath  504  is configured and arranged to mate with the dilator  506  such that the sheath  504  is disposed over at least a portion of the dilator  506 . In some embodiments, the dilator  506  nests within the sheath  504 . In preferred embodiments, the transverse cross-sectional shape of the dilator  506  matches the transverse cross-sectional shape of the sheath  504  to facilitate nesting of the dilator  506  within the sheath  504 . The sheath  504  mates with the dilator  506  such that the first end  522  of the dilator  506  extends axially from the first end  512  of the sheath  504 . The first end  510  of the sheath  504  can, optionally, be beveled or can include at least one sharp edge to facilitate the pushing apart of patient tissue during insertion of the introducer  502  into the patient. 
         [0052]    In at least some embodiments, the dilator  506  is configured and arranged to receive an epidural needle  540 . The epidural needle  540  is insertable into the second end  522  of the dilator  506  such that one end of the epidural needle  540  can be extended axially from the aperture  530 . The epidural needle  540  can be of any suitable bore including, for example, 14-gauge, 15-gauge, 16-gauge, 17-gauge, 18-gauge, 19-gauge, or larger. 
         [0053]      FIG. 5B  is a schematic perspective view of one embodiment of the epidural needle  540  disposed in the introducer  502 . The epidural needle  540  has a first end  550  and an opposing second end  552 . The epidural needle  540  defines a lumen  554  extending along a length of the epidural needle  540  between the first end  550  and the second end  552 . The lumen  554  of the epidural needle  540  can, optionally, be configured and arranged to receive a guide wire or lead blank  570 . 
         [0054]    The epidural needle  540  is insertable into the dilator  506  such that the first end  550  of the epidural needle  540  is extendable through the aperture  530  at the first end  520  of the dilator  506 . The first end  550  of the epidural needle  540  can be beveled to form a sharpened surface that facilitates initiating a path through patient tissue during insertion of the introducer  502  into a patient. The second end  552  of the epidural needle  540  can include a luer hub  556  configured and arranged to receive a syringe. For example, during insertion of the introducer  502 , fluid (e.g., saline solution, air, or the like) may be introduced or removed through the luer hub  556  to check for precise positioning of the introducer  502  (e.g., in an epidural space of the patient). 
         [0055]    The epidural needle  540  can be inserted into the dilator  506 , and the introducer  502  and epidural needle  540  can be inserted into the patient in proximity to the target stimulation region. The epidural needle  540  initiates a path and the dilator  506  pushes aside enough patient tissue to enable the sheath  504  to travel down the path. Once the introducer  502  is in proximity to a target stimulation location, the positioning of the introducer  502  may be checked (e.g., to confirm that the introducer  502  is disposed in an epidural space of the patient). 
         [0056]    The positioning of the introducer  502  may be checked in any suitable manner, such as by introducing or removing fluid through the luer hub  556  (e.g., performing a loss of resistance test), imaging (e.g., via fluoroscopy, magnetic resonance imaging, or the like) the patient with or without introducing one or more contrast agents into the patient, or using the electrodes of the lead (or another insertable stimulation device) to stimulate surrounding patient tissue. 
         [0057]    Optionally, at least one of the sheath  504  or the dilator  506  includes one or more radiopaque materials, for example, barium sulfate and bismuth subcarbonate, and the like or combinations thereof, that are incorporated into the introducer  502  to facilitate implantation of the paddle lead  107  through the use of one or more medical imaging techniques, such as fluoroscopy. 
         [0058]    Once the positioning of the introducer  502  is confirmed, the lead blank  570  can be inserted into the epidural needle  540  and guided to the target stimulation location. Once the desired pathway is established, the dilator  506  and epidural needle  540  can be removed along the second end  512  of the sheath  504 , thereby leaving the sheath  504  in proximity to the target stimulation location with the lead blank  570  disposed in the sheath  504 . 
         [0059]    The paddle lead  107  can then be inserted into the sheath  504  and guided to the target stimulation location. The lead blank  570  can be used to facilitate guidance of the paddle body  104  along the sheath  504 .  FIG. 6  is a schematic top view of one embodiment of one end of the lead blank  570  and a distal end of the paddle lead  107 . The distal end of the paddle lead  107  includes the lead bodies  106  coupled to the paddle body  104 . A paddle-body aperture  602  is defined along a length of the paddle body  104 . The paddle-body aperture  602  can be configured and arranged for receiving the lead blank  570 . Thus, the paddle body  104  can be threaded along the lead blank  570  while the paddle lead  104  is being guided along the sheath  504  to the target stimulation location. 
         [0060]    Optionally, one or more stylets can be used in addition to, or in lieu of, the lead blank  570  to facilitate guidance of the paddle body  104  along the sheath  504 . For example, it may be useful to use one or more stylets with a paddle lead with a single tail. The one or more stylets can be inserted into one or more lumens defined in one or more of the lead bodies  106  to stiffen the one or more lead bodies  106 , thereby facilitating guidance of the paddle lead  107  along the sheath  504 . Alternately, the paddle body  104  can be inserted into the sheath  504  without using either the lead blank  570  or one or more stylets to facilitate guidance of the paddle body  104 . 
         [0061]    Once the paddle body  104  is inserted into the sheath  504 , the lead blank  570  can be removed.  FIG. 7  is a schematic perspective view of one embodiment of a portion of the paddle lead  107  partially inserted into the sheath  504 . In  FIG. 7 , the paddle lead  107  is shown partially inserted into the sheath  504  such that the paddle body  104  extends from the first end  510  of the sheath  504  and the lead bodies  106  extends from the second end  512 . Optionally, the one or more stylets inserted into one or more lumens of the lead bodies  106  may be used to adjust or reposition the paddle body  104  at, or around, the target stimulation location. 
         [0062]    It will be understood that other techniques can be used for inserting the paddle lead  107  into the sheath  504 . For example, in an alternate embodiment the epidural needle  540  can be inserted into the patient&#39;s epidural space without the sheath  504  or the dilator  506 . Optionally, entry of the epidural needle  540  into the epidural space can be verified, as discussed above. The lead blank  570  can be inserted through the epidural needle  540 . The epidural needle  540  can be removed and the sheath  504  and dilator  506  can be placed over the lead blank  570 . The dilator  506  and the lead blank  570  can be removed, leaving the sheath  504  in the patient. The paddle lead  107  can then be inserted into the sheath  504 . 
         [0063]    Turning to  FIG. 8 , once the paddle lead  104  is inserted in the sheath  504  and repositioned (if necessary), the sheath  504  can be removed from the paddle lead  107 . The sheath  504  can be removed in any convenient manner. For example, the sheath  504  can be slid proximally along the paddle lead  107 , or the sheath  504  can be split apart, or otherwise cut, and removed (e.g., torn along the scored or perforated lines  516  or areas where it preferentially tears along a certain direction). 
         [0064]    For example,  FIG. 8  is a schematic perspective view of one embodiment of the sheath  504  being removed from the paddle body  104  by separating the tabs  518   a,    518   b  from one another. Separating the tabs  518   a,    518   b  causes the sheath  504  to separate along the scored or perforated lines  516 , thereby causing the sheath  504  to separate into two or more pieces that can be removed from the patient. 
         [0065]    The sheath  504  can be concurrently pulled proximally along the paddle lead  107  as the tabs  518   a,    518   b  are being separated. Eventually, the sheath  504  may be completely separated into two or more longitudinal strips, thereby separating completely from the paddle lead  107  and also from the patient. The sheath  504  can be extracted from the patient as the sheath  504  is split apart. The sheath  504  can be split apart without causing the paddle lead  107  to move. Optionally, the one or more stylets inserted into one or more lumens of the lead bodies  106  may be used to adjust the positioning of the paddle body  104  at the target stimulation location, if needed, and can then be removed from the one or more lead bodies  106 . 
         [0066]    Once the paddle lead  107  is positioned at the target stimulation site and the sheath  504  removed, the paddle lead  107  can be coupled to a control module (e.g.,  102  of  FIG. 1 ) and implanted using well-known techniques, for example, using one or more using tunneling straws placed in passageways underneath patient skin with bores that are sized large enough to receive the paddle lead  107 . In at least some embodiments, the paddle lead  107  can be coupled to a connector of a control module, as shown in  FIG. 2A . In other embodiments, the paddle lead  107  can be coupled to one or more other devices, including an adaptor, a lead extension (see e.g.,  FIG. 2B ), an operating room cable, or the like or combinations thereof. 
         [0067]      FIG. 9  is a schematic overview of one embodiment of components of an electrical stimulation system  900  including an electronic subassembly  910  disposed 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. 
         [0068]    Some of the components (for example, power source  912 , antenna  918 , receiver  902 , and processor  904 ) 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 source  912  can 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. 
         [0069]    As another alternative, power can be supplied by an external power source through inductive coupling via the optional antenna  918  or 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. 
         [0070]    If the power source  912  is a rechargeable battery, the battery may be recharged using the optional antenna  918 , if desired. Power can be provided to the battery for recharging by inductively coupling the battery through the antenna to a recharging unit  916  external to the user. Examples of such arrangements can be found in the references identified above. 
         [0071]    In one embodiment, electrical current is emitted by the electrodes  134  on the paddle or lead body to stimulate nerve fibers, muscle fibers, or other body tissues near the electrical stimulation system. A processor  904  is generally included to control the timing and electrical characteristics of the electrical stimulation system. For example, the processor  904  can, if desired, control one or more of the timing, frequency, strength, duration, and waveform of the pulses. In addition, the processor  904  can select which electrodes can be used to provide stimulation, if desired. In some embodiments, the processor  904  may select which electrode(s) are cathodes and which electrode(s) are anodes. In some embodiments, the processor  904  may be used to identify which electrodes provide the most useful stimulation of the desired tissue. 
         [0072]    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 unit  908  that, for example, allows modification of pulse characteristics. In the illustrated embodiment, the processor  904  is coupled to a receiver  902  which, in turn, is coupled to the optional antenna  918 . This allows the processor  904  to receive instructions from an external source to, for example, direct the pulse characteristics and the selection of electrodes, if desired. 
         [0073]    In one embodiment, the antenna  918  is capable of receiving signals (e.g., RF signals) from an external telemetry unit  906  which is programmed by a programming unit  908 . The programming unit  908  can be external to, or part of, the telemetry unit  906 . The telemetry unit  906  can 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 unit  906  may not be worn or carried by the user but may only be available at a home station or at a clinician&#39;s office. The programming unit  908  can be any unit that can provide information to the telemetry unit  906  for transmission to the electrical stimulation system  900 . The programming unit  908  can be part of the telemetry unit  906  or can provide signals or information to the telemetry unit  906  via 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 unit  906 . 
         [0074]    The signals sent to the processor  904  via the antenna  918  and receiver  902  can 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 system  900  to 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 antenna  918  or receiver  902  and the processor  904  operates as programmed. 
         [0075]    Optionally, the electrical stimulation system  900  may include a transmitter (not shown) coupled to the processor  904  and the antenna  918  for transmitting signals back to the telemetry unit  906  or another unit capable of receiving the signals. For example, the electrical stimulation system  900  may transmit signals indicating whether the electrical stimulation system  900  is operating properly or not or indicating when the battery needs to be charged or the level of charge remaining in the battery. The processor  904  may also be capable of transmitting information about the pulse characteristics so that a user or clinician can determine or verify the characteristics. 
         [0076]    The above specification, examples and data provide a description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention also resides in the claims hereinafter appended.