Patent Publication Number: US-2011071540-A1

Title: Lead with distal engagement feature to facilitate lead placement

Description:
FIELD 
     The present disclosure relates to implantable medical devices; more particularly to medical leads having a distal engagement element to facilitate placement of the lead during implantation. 
     BACKGROUND 
     Headaches, such as migraines, and occipital neuralgia are often incapacitating and may lead to significant consumption of drugs to treat the symptoms. However, a rather large number of people are unresponsive to drug treatment, leaving them to wait out the episode or to resort to coping mechanisms. For refractive occipital neuralgia, nerve ablation or separation may effectively treat the pain. 
     Occipital nerve stimulation may serve as an alternative for treatment of migraines or occipital neuralgia. For example, a dual channel implantable electrical generator may be implanted subcutaneously in a patient. A distal portion of first and second leads may be implanted in proximity to a left and right occipital nerve such that one or more electrode of the leads are in electrical communication with the occipital nerves. The proximal portions of the leads may then be connected to the signal generator such that electrical signals can be delivered from the signal generator to the electrodes to apply therapeutic signals to the occipital nerves. Alternatively, two single channel implantable electrical generators may be employed, where the first lead is connected to one signal generator and the second lead is connected to the second signal generator. In either case, the lead is typically tunneled subcutaneously from site of implantation of the signal generator to the occipital nerve or around the base of the skull. Such tunneling can be time consuming and is invasive. 
     Implanting the distal portions of the leads in proximity to a left and right occipital nerve such that one or more electrode of the leads are in electrical communication with the occipital nerves can be challenging or invasive, particularly with surgical leads or leads having paddle-shaped distal portions. Typically, an incision is made in the skin of the patient to allow for implantation of the distal portions of such leads. Because of the size and shape of the distal portions of paddle leads, they cannot be implanted using typical percutaneous techniques. It would be desirable to implant paddle or surgical leads in a patient in a less invasive manner. 
     BRIEF SUMMARY 
     The present disclosure describes, among other things, leads having an engagement element configured to cooperate with an engagement tool such that distal advancement of the engagement tool relative to the lead pushes the lead when the tool is engaged with the engagement element. Such engagement features may be particularly desirable for surgical or paddle leads having distal end portions that may be pushed through tissue of a patient for short distances. 
     In an embodiment, a method for pushing a distal portion of a lead through tissue of a patient is described. The distal portion of the lead has an electrode and an engagement element distal the electrode. The method includes engaging the engagement element of the lead with an engagement tool, and advancing the tool distally relative to the lead to push the distal portion of the lead through the tissue. The lead may be pushed by distal advancement of the tool until the electrode is positioned in a desired location of the tissue. 
     In an embodiment, a system for implanting a lead is described. The system includes a lead having a distal portion that includes an electrode and an engagement element distal the electrode. The system also includes an engagement tool having a lead engagement feature and an elongate member extending from the lead engagement feature such that distal advancement of the elongate member, when the lead engagement feature is engaged with the engagement element of the lead, pushes the lead distally. 
     In an embodiment, an implantable medical lead is described. The lead includes a proximal portion including a contact. The lead also includes a distal portion having a paddle-shaped portion, an electrode, and an engagement element configured to cooperate with a lead advancement tool to facilitate placement of the lead such that distal advancement of the tool relative to the lead pushes the lead distally. The electrode is electrically coupled to the contact, and the engagement element is distal to the electrode. The engagement element is integrally formed with the paddle-shaped portion. 
     In an embodiment, a method for applying electrical signals to left and right occipital nerves of a patient is described. The method includes implanting a lead including a proximal portion, a first distal arm, a second distal arm, and a branch region between the proximal portion and the first and second distal arms. The proximal portion includes first and second contacts. The first distal arm includes an electrode electrically coupled to the first contact and has an engagement element distal to the electrode. The second distal arm includes an electrode electrically coupled to the second contact and has an engagement element distal to the electrode. Implanting the lead includes engaging the engagement element of the first distal arm with a first engagement tool and advancing the tool distally relative to the lead to push the distal arm of the lead through tissue of the patient until the electrode is positioned adjacent to the left occipital nerve. Implanting the lead further includes engaging the engagement element of the second distal arm with a second engagement tool and advancing the tool distally relative to the lead to push the distal arm of the lead through tissue of the patient until the electrode is positioned adjacent to the right occipital nerve. The first and second engagement tools may be the same or may be different. The method further includes (i) operably coupling the first and second contacts of the proximal portion of the lead with an implantable signal generator; (ii) delivering a first signal generated by the signal generator to the left occipital nerve via the electrode of the first distal arm of the lead, and (iii) delivering a second signal generated by the signal generator to the right occipital nerve via the electrode of the second distal arm of the lead. The first and second signal may be the same or different. In some embodiments, a signal is delivered between the first and second electrodes to apply the signal to the left or right occipital nerve. 
     The leads, extensions, signal generators, systems and methods described herein provide one or more advantages over prior leads, extensions, signal generators, systems and methods. Such advantages will be readily understood from the following detailed description when read in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of an implantable system including a signal generator, lead extension and lead. 
         FIGS. 2A ,  3 , and  4 A are schematic top-down views of representative leads or distal portions of leads having an engagement element. 
         FIGS. 2B and 4B  are schematic bottom-up views of embodiments of (or alternatives of) distal portions of leads shown in  FIGS. 2A and 2B , respectively. 
         FIGS. 5 and 6A  are schematic side views of distal portions of leads having an engagement element. 
         FIG. 6B  is a schematic perspective view of an embodiment of the distal portion of the lead shown in  FIG. 6A . 
         FIGS. 7-9  are schematic side views of embodiments of engagement tools. 
         FIGS. 10A-C ,  11 A-B,  12 A-D, and  13 A-D are schematic views of engagement tools pushing leads via interaction with an engagement element. 
         FIGS. 14A-B  are schematic diagrams showing distal portions of bifurcated leads implanted in a subjects and positioned to apply an electrical signal to left and right occipital nerves. 
         FIG. 15A  is a schematic side view of a representative bifurcated lead. 
         FIGS. 15B-D  are schematic cross-sections of alternative embodiments of the proximal portion of the lead shown in  FIG. 15A  taken through line  15   b - 15   b.    
         FIG. 15E  is a schematic side view of an embodiment of the branch region of the lead depicted in  FIG. 15A , showing conductors running through the branch region. 
         FIGS. 16-17  are schematic side views of representative bifurcated leads. 
         FIGS. 18-19  are schematic side views of lead extensions having a connector configured to operably couple to leads and associated leads. 
         FIG. 20  is a schematic cross-section of a connector having receptacles for receiving leads. 
         FIGS. 21A-E  are schematic side views of representative bifurcated leads having extensible portions. 
         FIGS. 22A-F  are schematic side views of representative bifurcated leads having attached anchors. 
     
    
    
     The drawings are not necessarily to scale. Like numbers used in the figures refer to like components, steps and the like. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number. In addition, the use of different numbers to refer to components is not intended to indicate that the different numbered components cannot be the same or similar. 
     DETAILED DESCRIPTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration several specific embodiments of devices, systems and methods. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense. 
     All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure. 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     As used herein, “have”, “having”, “include”, “including”, “comprise”, “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to”. 
     “Exemplary” or “representative” is used herein in the sense of “for example” or “for the purpose of illustration”, and not in a limiting sense. 
     The present disclosure describes, among other things, leads having an engagement element configured to cooperate with an engagement tool such that distal advancement of the engagement tool relative to the lead pushes the lead when the tool is engaged with the engagement element. Such engagement features may be particularly desirable for surgical or paddle leads having distal end portions that may be pushed through tissue of a patient for short distances. 
     Nearly any implantable medical device or system employing leads may be used in conjunction with the leads described herein. Representative examples of such implantable medical devices include hearing implants, cochlear implants; sensing or monitoring devices; signal generators such as cardiac pacemakers or defibrillators, neurostimulators (such as spinal cord stimulators, brain or deep brain stimulators, peripheral nerve stimulators, vagal nerve stimulators, occipital nerve stimulators, subcutaneous stimulators, etc.), gastric stimulators; or the like. For purposes of occipital nerve stimulation, electrical signal generators such as Medtronic, Inc.&#39;s Restore® or Synergy® series of implantable neurostimulators may be employed. 
     Referring to  FIG. 1 , a schematic side view of a representative electrical signal generator system  100  is shown. In the depicted system  100 , the electrical signal generator  10  includes a connector header  15  configured to receive a proximal portion of lead extension  20 . The proximal portion of lead extension  20  contains a plurality of electrical contacts  22  that are electrically coupled to internal contacts (not shown) at distal connector  24  of lead extension  20 . The connector header  15  of the signal generator  10  contains internal contacts (not shown) and is configured to receive the proximal portion of the lead extension  20  such that the internal contacts of the connector header  15  may be electrically coupled to the contacts  22  of the lead extension  20  when the lead extension  20  in inserted into the header  15 . 
     The system depicted in  FIG. 1  further includes a lead  30 . The depicted lead  30  has a proximal portion that includes a plurality of contacts  32  and a distal portion that includes a plurality of electrodes  34 . Each of the electrodes  34  may be electrically coupled to a discrete contact  32 . The distal connector  24  of the lead extension  20  is configured to receive the proximal portion of the lead  30  such that the contacts  32  of the lead  30  may be electrically coupled to the internal contacts of the connector  24  of the extension  20 . Accordingly, a signal generated by the signal generator  10  may be transmitted to a patient by an electrode  34  of lead  30  when lead is connected to extension  20  and extension  20  is connected to signal generator  10 . 
     It will be understood that lead  30  may be coupled to signal generator  10  without use of an extension  20 . Any number of leads  30  or extensions  20  may be coupled to signal generator  10 . Typically, one or two leads  30  or extensions  20  are coupled to signal generator  10 . While lead  20  is depicted as having four electrodes  34 , it will be understood that lead  30  may include any number of electrodes  34 , e.g. one, two, three, four, five, six, seven, eight, sixteen, thirty-two, or sixty-four. Corresponding changes in the number of contacts  32  in lead  30 , contacts  22  and internal contacts in connector  24  of lead extension, or internal contacts in connector  15  of signal generator  10  may be required or desired. 
     Referring now to  FIGS. 2-6 , various schematic views of leads  30  or distal portions  320  thereof, having engagement elements  1010  are shown. As shown in  FIG. 2A , the leads  30  include proximal portions  310  having one or more contacts  32  and distal portions  320  having one or more electrodes  34  operably coupled to the contacts  32 , e.g. as described above. As further shown in  FIG. 2A , the depicted leads  320  include paddle-shaped portions  330 . The paddle shaped portion  330  includes the one or more electrodes  34  and the engagement element  1010 . The engagement element  1010  is distal to the distal most electrode. The engagement element  1010  may be integrally formed with the paddle-shaped portion  330  or attached to the paddle-shaped portion (e.g., adhered, fastened, integrally formed, or otherwise secured). 
     With reference to  FIGS. 2A ,  3 , and  4 A, schematic top-down views of representative leads  30  or distal portions  320  of leads having a variety of engagement element  1010  configurations are shown. As depicted in  FIG. 3 , the engagement element  1010  may form a hole that may be engaged by a lead advancement tool, such as a tool may have, for example, a hook. In the embodiment depicted in  FIG. 4A , the engagement element  1010  includes or consists of a slit in the paddle-shaped portion  330  of the lead. A lead advancement tool may be inserted into the body of the paddle  330  to push the paddle to a desired implant location. In the embodiments depicted in  FIGS. 2A and 4A , the engagement element  1010  extends from or is on the surface of the paddle  330  through which the electrodes are exposed. Typically paddle-shaped leads have electrodes exposed through one surface of the paddle, but not through the opposing surface. As shown in the embodiments depicted in  FIGS. 2B and 4B , an engagement element  1010  may alternatively or additionally extends from, or may be on, the opposing surface of the paddle  330  through which the electrodes are not exposed. 
     Referring now to  FIGS. 5 and 6A , schematic side views of alternative embodiments the distal portion of the lead depicted in  FIG. 2B  are shown. The engagement element  1010  extends from a major surface of the paddle  330 . As depicted in  FIG. 5 , the engagement element  1010  forms a cavity  1020  configured to receive an engagement tool. 
     Referring to  FIG. 6B , a schematic perspective view of an embodiment of the paddle-shaped portion  330  of the lead depicted in  FIG. 6A  is shown. As with the engagement element depicted in  FIG. 5 , the engagement element  1010  depicted in  FIG. 6A  forms a cavity configured to receive an engagement tool. The cavity  1020  depicted in  FIG. 6B  is formed by first  1210 , second  1220 , and third  1230  side walls, a floor  1110 , which may be even with the major surface of the paddle  330  or may be recessed relative to the major surface, and a ceiling  1100 . The cavity  1020  depicted in  FIG. 6B , or other similar cavities, allow the portion of an engagement tool received by the cavity  1020  to engage a variety of surfaces  1100 ,  1110 ,  1210 ,  1220 ,  1230  to allow for steering or guiding of the distal portion of the lead as it is pushed through tissue of a patient by the tool. 
     It will be understood that the engagement elements  1010  depicted in  FIGS. 2-6  are merely examples of engagement elements that may be employed in accordance with the teaching presented herein. Any other engagement element having a suitable configuration for engaging a portion of an engagement tool such that, when engaged by the tool, distal advancement of the tool pushes the distal portion of the lead distally. 
     It will be further understood that a lead engagement element may be positioned at any suitable location of the distal portion of the lead. Placing the engagement element distal to the distal most electrode or at or near the distal end of the lead allows for the remainder of the lead to be pulled through the patient&#39;s tissue by the pushing force applied to the distally located engagement element. However, if the lead is suitable designed (e.g., sufficiently rigid) to be pushed from a more proximal location, the engagement element may be place in a location more proximal than at or near the distal end of the lead. It will also be understood that an engagement element may be incorporated at any suitable position of a lead, such as the side or mid-body of the paddle portion. It will be further understood that the percutaneous leads, having generally cylindrical distal portions, or leads other that surgical or paddle leads may include engagement elements and may be implanted as described herein. 
     Engagement elements may be formed of any suitable material. In various embodiments, an engagement element is formed of material that forms the body of the paddle, such as polymeric material. Reinforcing elements may be included in the engagement members to provide sufficient structural rigidity to allow the lead to be pushed through tissue of the patient. 
     Referring now to  FIGS. 7-9 , schematic side views of alternative embodiments of engagement tools  700  are shown. The tools  700  have a lead engagement feature  720  configured to engage an engagement element of a lead. The tools  700  also include elongate members  710  that extend proximally from the lead engagement feature  720 . In various embodiments, the lead engagement feature  720  is the distal end of the elongate member  710 . As shown in  FIGS. 8-9 , the elongate members may include a curved portion  730 . In some embodiments, the tools  700  are preformed to include the curved portion  730 . In some embodiments, the elongate members  710  are configured to be manually bent to include a curve portion  730 , as needed or desired, by a physician or other health care provider during the implant procedure. The tool  700  depicted in  FIG. 9  is bent in a manner such that pulling on a portion, such as the loop  740 , of the elongate member  710  distal to the engagement feature  720  cause a portion of the elongate member  710  proximal to the engagement feature  720  to push the engagement feature. 
     It will be understood that  FIGS. 7-9  depict only some examples of suitable configurations for engagement tools that may be employed as described herein. Any other suitable form or configuration of engagement tool may be employed. 
     An engagement tool may be formed from any suitable material, such as a rigid polymeric material, a metallic material, combinations thereof, or the like. Preferably, the engagement tool is formed of material sufficiently stiff to push a lead through subcutaneous tissue of a patient, yet flexible enough to bend as may be needed during implantation. 
     Referring now to  FIGS. 10A-C , side views illustrating a tool pushing a distal portion of a lead (only distal portion shown for purposes of brevity, simplicity, and clarity). As shown in  FIG. 10A-B , the elongate member  710  in proximity to the engagement feature  720  of a tool may be advanced distally relative to the lead until the engagement feature engages the engagement member  1010  of the paddle-shaped portion  330  of the lead. As shown in  FIGS. 10B-C , further distal advancement of the elongate member  710  relative to the lead, when the tool is engaged with the engagement element  1010 , causes the distal portion of the lead (including the paddle  330  in the depicted embodiment) to move distally. Position “X” indicated in  FIGS. 10B-C  is intended to mark a stationary position to reflect movement of the paddle portion  330  of the lead, and the elongate member  710  is pushed against the engagement feature  1010 . 
       FIGS. 11A-B  illustrate another example of a tool  700  moving a lead (only the distal portion  320  is shown for the purposes of brevity, simplicity, and clarity). The elongate member  710  distal to the engagement element  720  is pulled, e.g. by pulling on loop  740 , to cause the elongate member  710  in proximity to the engagement feature  720  of the tool  700  to push the engagement feature  720 . When the engagement feature  720  engages the engagement element  1010  at the distal portion  320  of the lead, distal advancement of the tool, causes the distal portion  320  of the lead to be moved distally. 
     Referring now to  FIGS. 12A-D  and  FIGS. 13A-D , schematic drawings illustrating the advancement of a distal portion  320  of a lead  30  through tissue of a subject are shown.  FIGS. 13A-D  are substantially the same as  FIGS. 12A-D , except that the orientation of the lead  30  is slightly different. It will be understood that only the distal portion  320  of the lead is shown in  FIGS. 12B-D  and  FIGS. 13B-D  for purposes of brevity, simplicity and clarity. As in  FIGS. 10-11 , the distal portion  320  of the lead includes and engagement element  1010  configured to cooperate with a tool  700  to advance the distal portion  320  of the lead through tissue  800  of a patient. The distal portion  320  of the lead  30  may be inserted through an incision  820  made in the patient. In the depicted embodiment, the incision  820  is through the skin  810  allowing advancement and implantation of the lead  30  in subcutaneous tissue  800  of the patient. A tool  700  (e.g. as described above) may be used to facilitate initial insertion into the subcutaneous tissue  800  (see, e.g.,  FIG. 12B ,  13 B) and is used to advance the distal portion  320  of the lead through the tissue  300  (see, e.g.,  FIGS. 12C-D ,  13 C-D). As the distal portion  320  of the lead enters the tissue  800  and is pushed through the tissue  800 , the angle of the tool  700  (compare  FIGS. 12B-D ,  13 B-D) is manipulated to implant the distal portion  320  of the lead at the appropriate angle and depth within the tissue  800 . In the depicted embodiment, the tool  700  is pre-bent or curved. However, in various embodiments, the tool  700  may be bent or curved manually as needed or desired. Once the distal portion  320  of the lead is advanced to the desired location within the tissue  800 , the tool  700  may be removed. 
     In some embodiments, the tool may be removed simply by withdrawing the tool from the tissue. However, in some embodiments, the engagement element of the lead and the engagement feature of the tool may be configured such that a significant amount of force is needed to disengage the tool from the engagement element of the lead (e.g., a compression fit, interference fit, snap fit, or the like). In such embodiments, it may be necessary to employ another tool to hold the distal portion on the lead in place while the engagement tool is disengaged to prevent movement of the distal portion of the lead from its desired implant location. Any suitable additional tool, such as forceps, pliers or the like to hold the paddle portion or the like, may be employed. Alternatively or in addition, the tool may have a mechanical disengaging mechanism to release the lead. 
     Referring now to  FIGS. 14A-B , a bifurcated lead  400  is shown implanted in a patient to provide bilateral therapy to left and right occipital nerves  200 . As used herein, occipital nerve  200  includes the greater occipital nerve  210 , the lesser occipital nerve  220  and the third occipital nerve  230 . The greater and lesser occipital nerves are spinal nerves arising between the second and third cervical vertebrae (not shown). The third occipital nerve arises between the third and fourth cervical vertebrae. The portion of the occipital nerve  200  to which an electrical signal is to be applied may vary depending on the disease to be treated and associated symptoms or the stimulation parameters to be applied. In various embodiments, the lead distal portions  450  that contain electrodes are placed to allow bilateral application of electrical signals to the occipital nerve  200  at a level of about C 1  to about C 2  or at a level in proximity to the base of the skull. The position of the electrode(s) may vary. It will be understood that the electrode need not, and in various embodiments preferably does not, contact the nerve to apply the signal to the nerve. It will be further understood that a signal may be applied to any suitable portion of an occipital nerve, whether at a trunk, branch, or the like. In various embodiments, one or more electrodes are placed between about 1 cm and about 8 cm from the midline to effectively provide an electrical signal to the occipital nerve  200 . 
     As shown in  FIG. 14A , a bifurcated lead  400  may include a paddle shaped distal portion  450  containing electrodes. Such paddle shaped leads are often referred to as surgical leads. Examples of surgical leads that may be modified to form paddle leads as described herein include Medtronic Inc.&#39;s Resume, SymMix, On-Point, or Specify series of leads. Surgical leads typically contain electrodes that are exposed through one face of the paddle, providing directional stimulation. The depicted bifurcated lead  200  also includes a single proximal portion  410  that allows for only one tunneling procedure to the signal generator (not shown) implant site. In addition, the bifurcated lead  400  contains a branch region  440  and first  420  and second  430  distal arms. As shown in  FIG. 14B , the bifurcated lead may include distal portion  450  that include electrodes that are generally cylindrically shaped. Such leads are often referred to percutaneous leads. Examples of percutaneous leads that may be modified to form leads as described herein include Medtronic Inc.&#39;s Quad Plus, Pisces Quad, Pisces Quad Compact, or 1×8 SubCompact, 1×8 Compact, and 1×8 Standard leads. Such percutaneous leads typically contain ring electrodes that apply an electrical stimulation signal to tissue in all directions around the ring. Accordingly, the amplitude of the signal (and thus the energy required from the signal generator) applied may be greater with percutaneous leads that surgical leads for occipital nerve therapies. 
     While not shown, the leads  400  depicted in  FIGS. 14A-B  may include engagement elements, as described above, and the distal arms  450 ,  451  may be implanted with the use of an engagement tool, as described above. For example, an incision may be made along the midline of the patient&#39;s neck, and the distal portions  450 ,  451  may be pushed in place subcutaneously using an engagement tool. The proximal portion of the lead  410  may be tunneled to a location in which an implantable signal generator is implanted or is to be implanted. 
     Various embodiments of bifurcated leads that may contain engagement features are described below with regard to  FIGS. 15-19 . Such leads may be used to apply electrical signal therapy to occipital nerves or other nerves or other targets. As with the non-bifurcated leads described above, it will be understood that the leads depicted in  FIGS. 15-19  are merely examples of leads that may contain an engagement element. 
     Referring now to  FIG. 15A , a side view of a representative bifurcated lead  400  is shown. The lead  400  includes a proximal portion  410  that includes a plurality of contacts  450  for electrically coupling to an electrical signal generator or a lead extension or an adaptor. The lead also includes first  420  and second  430  distal arms that contain an engagement element  1010  and electrodes  424 ,  434 . The electrodes  424 ,  434  are electrically coupled to contacts  450  via conductors that run within lead  400  from the contacts  450  to the electrodes  424 ,  434 . The lead  400  further includes a branch region  440  where the lead  400  transitions from the proximal portion  410  to the distal arms  420 ,  430 . The branch region  440  may be of any suitable size and shape. In various embodiments, the branch region  440  has a volume of less than about 10 cubic centimeters; e.g., less than about 5 cubic centimeters. 
     The branch region  440  includes a first entry region  442  where the proximal portion  410  of the lead enters the branch region. The branch region  440  also includes second  344  and third  346  entry regions where the first  420  and second  430  distal arms enter the branch region. A plane runs through the centers of the entry regions  442 ,  444 ,  446 . The angle of either of the second  444  and third  446  entry regions from a line extending in the plane and aligned with the geometric center first entry point  442  as it extends to proximal portion  410  of the lead  400  is between about 90 degrees and 180 degrees. In some embodiments, the center of the second  444  or third  446  entry region is substantially perpendicular to the line extending in the plane and aligned with the geometric center first entry point  442  (see, e.g.,  FIG. 16 ). In some embodiments, the angle of the second  444  or third  446  entry region relative to the first entry point  442  is between about 110 degrees and about 160 degrees. 
     Referring now to  FIG. 15B-D , which is a cross section of the proximal portion  410  of the lead  400  depicted in  FIG. 15A  taken along line  15   b - 15   b , showing representative configurations. As shown in  FIG. 15B , the proximal portion of the lead includes a lead body  412 . The lead body  412  may include two lumens or tubes  414 A,  414 B (or any number of tubes or lumens, e.g. one for each conductor) through which or around which conductors (not shown) may run to connect proximal contacts with electrodes of the first and second distal arms. Of course, the lumens or tubes  414 A,  414 B may be solid and the conductors can run in separate tracks along the length of the proximal portion of the lead until connecting with the distal arms. Alternatively, as shown in  FIG. 15C , the lead body  412  in the proximal portion may include a single lumen  416  or solid core (not shown) and the conductors (not shown) may run in a single track along the along the length of the proximal portion of the lead. Alternatively as shown in  FIG. 15D , the proximal portion of the lead may include two attached lead bodies  412 A,  412 B through which separate channels of conductors (not shown) run. Of course, the lead body of the proximal portion of lead body may be configured in any other suitable manner. 
     Referring now to  FIG. 15E , a representative example of a branch region  440  is shown in which the branch region  440  is transparent for purposes of illustration. In the depicted embodiment, a set of conductors  470  exit a lead body from the proximal portion  410  of the lead. The set of conductors  470  are separated into subsets  470   a ,  470   b  that independently enter lead bodies of the first  420  and second  430  distal arms. Any suitable manner of forming branch region  440  and separating conductors  470  for entry of subsets  470   a ,  470   b  into distal arms  420 ,  430  may be employed. For example, a lead body containing conductors  470  in proximal portion  410  may be formed. Additional lead bodies containing conductor subsets  470   a ,  470   b  forming distal arms  420 ,  430  may be formed. The conductor subsets  470   a ,  470   b  may be appropriately electrically coupled to the set of conductors  470  and branch region  440  may be overmolded over conductors  470 ,  470   a ,  470   b , resulting in branch region  440  as depicted. Of course, any other suitable process may be employed to form branch region  440  and appropriately electrically couple proximal portion  410  of the lead to the distal arms  420 ,  430 . 
     Referring now to  FIG. 16 , a side view of a representative lead  400  is shown. The lead  400  includes a proximal portion  410  including contacts  450 , a first distal arm  420  having a region  422  containing an engagement element  1010  and electrodes  424 , a second distal arm  430  having a region  432  containing an engagement element  1010  and electrodes  434 , and a branch point  440  where the lead  400  transitions from the proximal portion  410  to the first  420  and second  430  distal arms. The distal arms  420 ,  430  exit the branch point  440  substantially perpendicular to the entry of the proximal portion  410  in the depicted embodiment. The distal portions  422 ,  432  containing the electrodes  424 ,  434  are paddle-shaped in the embodiment depicted in  FIG. 16 . Of course, distal portions containing the electrodes may have any suitable shape, such as cylindrical. 
     Referring now to  FIG. 17 , a lead  410  may include one or more anchors  460  for facilitating retention of the lead to tissue into which it is implanted. In  FIG. 17 , the anchors  460  are depicted as suture holes or tines, but the anchors may take any suitable form. In various embodiments, an anchor  460  is attached to branch region  440 . As used herein, “attached” includes “integrally formed with.” For application of therapies to an occipital nerve, where proximal portion  410  is tunneled through the neck region of a subject, it may be desirable to securely anchor branch region  440  to tissue of the subject to prevent movement of the lead (and thus proximal portion  410 ) from causing movement of distal arms  420 ,  430  or portions thereof. In addition, it may be desirable for proximal portion to contain a strain relief feature to allow for stretching and movement of the next (and thus proximal portion  410 ) from transferring excessive force to branch region  440 . For example, proximal portion  410  may include a sigma shaped portion  470 , may be looped (not shown), or may be extensible. One or more anchors  460  may be attached to first  420  or second  430  distal arms or to portions thereof, such as the distal portions containing electrodes as depicted. 
     Referring now to  FIGS. 18-19 , a schematic drawing of bifurcating lead extensions  600  and associated leads  400 A and  400 B are shown. Bifurcating lead extensions  600  as described herein have many of the advantages discussed above with regard to bifurcating leads. For example, only one tunneling procedure is needed to proximal portion  610  of extension  600  to the site of implantation of signal generator. The proximal portion  610  of the extension  600  includes contacts  650  for electrical coupling the extension  600  to the signal generator. The distal portion of extension  600  includes a connector  640  containing two lead receptacles (not shown) having internal contacts for coupling to contacts  450 A,  450 B of leads  400 A,  400 B. The connector  600  may be of any suitable size and shape. In various embodiments, the connector  600  has a volume of less than about 10 cubic centimeters; e.g. less than about 5 cubic centimeters. Set screws  642 A,  642 B may be used to secure leads  400 A,  400 B in receptacles. Of course, any other suitable mechanism for securing leads  400 A,  400 B in receptacles may be employed. In the embodiment depicted in  FIG. 19 , the lead receptacles (not shown) are generally perpendicular to the angle of entry of the proximal portion  610  into connector  640 . 
     Leads  400 A,  400 B include proximal portions  410 A,  410 B containing contacts  450 A,  450 B and distal portions  422 A,  422 B containing electrodes  424 A,  424 B and an engagement element  1010 . By employing a bifurcating extension  600  and separate leads  400 A,  400 B standard introducer tools, such as needle introducers with lumens (provided that the distal portion of the lead fits within the lumen), may be used to position distal portion  424 A,  424 B of leads  400 A,  400 B. For bifurcating leads alternative methods for introducing distal portions may be desired. 
     Referring now to  FIG. 20 , a schematic cross-section of a connector portion  700  of a lead extension; e.g. connector  640  as depicted in  FIG. 19 , is shown. Connector  700  includes first  710  and second  720  lead receptacles. The receptacles  710 ,  720  include openings on opposing ends of connector  700  for inserting leads in to the receptacles  710 ,  720  and include internal contacts  712 ,  722  for electrically coupling to contacts of leads when inserted into the receptacles  710 ,  720 . 
     Referring now to  FIGS. 21-22 , various representative configurations of bifurcated leads are shown. However, it will be understood that the configurations presented may also be applied to bifurcating extensions. Further, while T-shaped configurations are depicted, it will be understood that such configurations are readily applicable to Y- or other shaped configurations. Engagement elements are not shown in the leads depicted in  FIGS. 21-22 , however, it will be understood that the leads may include engagements elements, e.g. as described above. In the embodiments depicted in  FIGS. 21A-E , the bifurcated leads include a proximal portion  410  containing contacts (not shown), a branch region  440  and first  420  and second  430  distal arms containing electrodes (not shown). The squiggly lines depicted in  FIGS. 21B-E  represent extensibility of the lead of that squiggly portion. Extensibility may include a sigma shaped section, loops, or may otherwise be configured to be extensible. As depicted, proximal portion  410  or distal arms  420 ,  430  or portions thereof may be extensible. 
     As shown in  FIGS. 22A-F , in which circles represent attached anchors  460 , a bifurcated lead may include one or more attached anchor at nearly any location of the lead, such as the distal portion or along the length of a distal arm  420 ,  430 , at a branch region  440 , or anywhere along the proximal portion  410 . It will be understood that possible combinations of the configurations shown in  FIGS. 21-22  are contemplated, as are combinations of other figured depicted and discussed herein. 
     Thus, embodiments of LEAD WITH DISTAL ENGAGEMENT ELEMENT TO FACILITATE LEAD PLACEMENT are disclosed. One skilled in the art will appreciate that the leads, extensions, connectors, devices such as signal generators, systems and methods described herein can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation.