Patent Publication Number: US-9427567-B2

Title: Leads with electrode carrier for segmented electrodes and methods of making and using

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/517,599 filed Oct. 17, 2014, which issued as U.S. Pat. No. 9,227,050, which is a continuation of U.S. patent application Ser. No. 13/951,057 filed Jul. 25, 2013, which issued as U.S. Pat. No. 8,897,891 on Nov. 25, 2014, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/679,264 filed on Aug. 3, 2012, all of which are incorporated herein by reference. 
    
    
     FIELD 
     The invention is directed to the area of electrical stimulation systems and methods of making and using the systems. The present invention is also directed to electrical stimulation leads with segmented electrodes that can be used for directed electrical stimulation, as well as methods of making and using the segmented electrodes, leads, and electrical stimulation systems. 
     BACKGROUND 
     Electrical stimulation can be useful for treating a variety of conditions. Deep brain stimulation can be useful for treating, for example. Parkinson&#39;s disease, dystonia, essential tremor, chronic pain. Huntington&#39;s Disease, levodopa-induced dyskinesias and rigidity, bradykinesia, epilepsy and seizures, eating disorders, and mood disorders. Typically, a lead with a stimulating electrode at or near a tip of the lead provides the stimulation to target neurons in the brain. Magnetic resonance imaging (“MRI”) or computerized tomography (“CT”) scans can provide a starting point for determining where the stimulating electrode should be positioned to provide the desired stimulus to the target neurons. 
     After the lead is implanted into a patient&#39;s brain, electrical stimulus current can be delivered through selected electrodes on the lead to stimulate target neurons in the brain. Typically, the electrodes are formed into rings disposed on a distal portion of the lead. The stimulus current projects from the ring electrodes equally in every direction. Because of the ring shape of these electrodes, the stimulus current cannot be directed to one or more specific positions around the ring electrode (e.g., on one or more sides, or points, around the lead). Consequently, undirected stimulation may result in unwanted stimulation of neighboring neural tissue, potentially resulting in undesired side effects. 
     BRIEF SUMMARY 
     One embodiment is a stimulation lead that includes a lead body having a longitudinal length, a distal portion, and a proximal portion; terminals disposed along the proximal portion of the lead body; an electrode carrier coupled to, or disposed along, the distal portion of the lead body; segmented electrodes disposed along the electrode carrier; and conductors extending along the lead body and coupling the segmented electrodes to the terminals. The electrode carrier includes a lattice region defining segmented electrode receiving openings. Each of the segmented electrodes extends around no more than 75% of a circumference of the lead and is disposed in a different one of the segmented electrode receiving openings of the electrode carrier. Optionally, the stimulation lead can include one or more ring electrodes disposed on the electrode carrier and coupled via one or more conductors to the terminals. 
     Another embodiment is a method of making a stimulation lead. The method includes providing an electrode carrier having a lattice region defining multiple segmented electrodes receiving openings; and disposing segmented electrodes in the segmented electrode receiving openings. Each of the segmented electrodes extends around no more than 75% of a circumference of the lead and each of the segmented electrodes is disposed in a different one of the segmented electrode receiving openings of the electrode carrier. The method also includes electrically coupling conductors to the segmented electrodes and electrically coupling the conductors to terminals disposed along an opposing end of the lead. Optionally, the method can include disposing one or more ring electrodes on the electrode carrier and electrically coupling the one or more ring electrodes to the terminals via one or more conductors. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
       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: 
         FIG. 1  is a schematic side view of one embodiment of a device for brain stimulation, according to the invention; 
         FIG. 2  is a schematic diagram of radial current steering along various electrode levels along the length of a lead, according to the invention; 
         FIG. 3A  is a perspective view of an embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention: 
         FIG. 3B  is a perspective view of a second embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention: 
         FIG. 3C  is a perspective view of a third embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention; 
         FIG. 3D  is a perspective view of a fourth embodiment of a portion of a lead having a plurality of segmented electrodes, according to the invention: 
         FIG. 4  is a schematic perspective view of one embodiment of an electrode carrier, according to the invention: 
         FIG. 5A  is a schematic exploded perspective view of one embodiment of a portion of lead illustrating an electrode carrier and associated segmented and ring electrodes, according to the invention: 
         FIG. 5B  is a schematic exploded perspective view of one embodiment of a portion of lead illustrating an electrode carrier and selected segmented and ring electrodes with associated conductors, according to the invention; and 
         FIG. 5C  is a schematic perspective view of one embodiment of a portion of a lead showing the electrode carrier with electrodes attached to a remainder of the lead, according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The invention is directed to the area of electrical stimulation systems and methods of making and using the systems. The present invention is also directed to electrical stimulation leads with segmented electrodes that can be used for directed electrical stimulation, as well as methods of making and using the segmented electrodes, leads, and electrical stimulation systems. 
     A lead for deep brain stimulation may include stimulation electrodes, recording electrodes, or a combination of both. At least some of the stimulation electrodes, recording electrodes, or both are provided in the form of segmented electrodes that extend only partially around the circumference of the lead. These segmented electrodes can be provided in sets of electrodes, with each set having electrodes radially distributed about the lead at a particular longitudinal position. For illustrative purposes, the leads are described herein relative to use for deep brain stimulation, but it will be understood that any of the leads can be used for applications other than deep brain stimulation, including spinal cord stimulation, peripheral nerve stimulation, or stimulation of other nerves and tissues. 
     Suitable implantable electrical stimulation systems include, but are not limited to, a least one 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. Examples of electrical stimulation systems with leads are found in, for example, U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029; 6,609,032; 6,741,892; 7,244,150; 7,450,997; 7,672,734; 7,761,165; 7,783,359; 7,792,590; 7,809,446; 7,949,395; 7,974,706; 8,175,710; 8,224,450; 8,271,094; 8,295,944; 8,364,278; and 8,391,985; U.S. Patent Applications Publication Nos. 2007/0150036; 2009/0187222; 2009/0276021; 2010/0076535; 2010/0268298; 2011/0004267; 2011/0078900; 2011/0130817; 2011/0130818; 2011/0238129; 2011/0313500; 2012/0016378; 2012/0046710; 2012/0071949; 2012/0165911; 2012/0197375; 2012/0203316; 2012/0203320; 2012/0203321; 2012/0316615; and 2013/0105071; and U.S. patent application Ser. Nos. 12/177,823 and 13/750,725, all of which are incorporated by reference. 
     In at least some embodiments, a practitioner may determine the position of the target neurons using recording electrode(s) and then position the stimulation electrode(s) accordingly. In some embodiments, the same electrodes can be used for both recording and stimulation. In some embodiments, separate leads can be used; one with recording electrodes which identify target neurons, and a second lead with stimulation electrodes that replaces the first after target neuron identification. In some embodiments, the same lead may include both recording electrodes and stimulation electrodes or electrodes may be used for both recording and stimulation. 
       FIG. 1  illustrates one embodiment of a device  100  for brain stimulation. The device includes a lead  110 , a plurality of electrodes  125  disposed at least partially about a circumference of the lead  110 , a plurality of terminals  135 , a connector  132  for connection of the electrodes to a control unit, and a stylet  140  for assisting in insertion and positioning of the lead in the patient&#39;s brain. The stylet  140  can be made of a rigid material. Examples of suitable materials for the stylet include, but are not limited to, tungsten, stainless steel, and plastic. The stylet  140  may have a handle  150  to assist insertion into the lead  110 , as well as rotation of the stylet  140  and lead  110 . The connector  132  fits over a proximal end of the lead  110 , preferably after removal of the stylet  140 . 
     The control unit (not shown) is typically an implantable pulse generator that can be implanted into a patient&#39;s body, for example, below the patient&#39;s clavicle area. The pulse generator can have eight stimulation channels which may be independently programmable to control the magnitude of the current stimulus from each channel. In some cases the pulse generator may have more or fewer than eight stimulation channels (e.g., 4-, 6-, 16-, 32-, or more stimulation channels). The control unit may have one, two, three, four, or more connector ports, for receiving the plurality of terminals  135  at the proximal end of the lead  110 . 
     In one example of operation, access to the desired position in the brain can be accomplished by drilling a hole in the patient&#39;s skull or cranium with a cranial drill (commonly referred to as a burr), and coagulating and incising the dura mater, or brain covering. The lead  110  can be inserted into the cranium and brain tissue with the assistance of the stylet  140 . The lead  110  can be guided to the target location within the brain using, for example, a stereotactic flame and a microdrive motor system. In some embodiments, the microdrive motor system can be fully or partially automatic. The microdrive motor system may be configured to perform one or more the following actions (alone or in combination): insert the lead  110 , retract the lead  110 , or rotate the lead  110 . 
     In some embodiments, measurement devices coupled to the muscles or other tissues stimulated by the target neurons, or a unit responsive to the patient or clinician, can be coupled to the control unit or microdrive motor system. The measurement device, user, or clinician can indicate a response by the target muscles or other tissues to the stimulation or recording electrode(s) to further identify the target neurons and facilitate positioning of the stimulation electrode(s). For example, if the target neurons are directed to a muscle experiencing tremors, a measurement device can be used to observe the muscle and indicate changes in tremor frequency or amplitude in response to stimulation of neurons. Alternatively, the patient or clinician may observe the muscle and provide feedback. 
     The lead  110  for deep brain stimulation can include stimulation electrodes, recording electrodes, or both. In at least some embodiments, the lead  110  is rotatable so that the stimulation electrodes can be aligned with the target neurons after the neurons have been located using the recording electrodes. 
     Stimulation electrodes may be disposed on the circumference of the lead  110  to stimulate the target neurons. Stimulation electrodes may be ring-shaped so that current projects from each electrode equally in every direction from the position of the electrode along a length of the lead  110 . Ring electrodes typically do not enable stimulus current to be directed to only one side of the lead. Segmented electrodes, however, can be used to direct stimulus current to one side, or even a portion of one side, of the lead. When segmented electrodes are used in conjunction with an implantable pulse generator that delivers constant current stimulus, current steering can be achieved to more precisely deliver the stimulus to a position around an axis of the lead (i.e., radial positioning around the axis of the lead). 
     To achieve current steering, segmented electrodes can be utilized in addition to, or as an alternative to, ring electrodes. Though the following description discusses stimulation electrodes, it will be understood that all configurations of the stimulation electrodes discussed may be utilized in arranging recording electrodes as well. 
     The lead  100  includes a lead body  110 , one or more optional ring electrodes  120 , and a plurality of sets of segmented electrodes  130 . The lead body  110  can be formed of a biocompatible, non-conducting material such as, for example, a polymeric material. Suitable polymeric materials include, but are not limited to, silicone, polyurethane, polyurea, polyurethane-urea, polyethylene, or the like. Once implanted in the body, the lead  100  may be in contact with body tissue for extended periods of time. In at least some embodiments, the lead  100  has a cross-sectional diameter of no more than 1.5 mm and may be in the range of 1 to 1.5 mm. In at least some embodiments, the lead  100  has a length of at least 10 cm and the length of the lead  100  may be in the range of 25 to 70 cm. 
     The electrodes may be made using a metal, alloy, conductive oxide, or any other suitable conductive biocompatible material. Examples of suitable materials include, but are not limited to, platinum, platinum iridium alloy, iridium, titanium, tungsten, palladium, palladium rhodium, or the like. Preferably, the electrodes are made of a material that is biocompatible and does not substantially corrode under expected operating conditions in the operating environment for the expected duration of use. 
     Each of the electrodes can either be used or unused (OFF). When the electrode is used, the electrode can be used as an anode or cathode and carry anodic or cathodic current. In some instances, an electrode might be an anode for a period of time and a cathode for a period of time. 
     Stimulation electrodes in the form of ring electrodes  120  may be disposed on any part of the lead body  110 , usually near a distal end of the lead  100 . In  FIG. 1 , the lead  100  includes two ring electrodes  120 . Any number of ring electrodes  120  may be disposed along the length of the lead body  110  including, for example, one, two three, four, live, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen or more ring electrodes  120 . It will be understood that any number of ring electrodes may be disposed along the length of the lead body  110 . In some embodiments, the ring electrodes  120  are substantially cylindrical and wrap around the entire circumference of the lead body  110 . In some embodiments, the outer diameters of the ring electrodes  120  are substantially equal to the outer diameter of the lead body  110 . The length of the ring electrodes  120  may vary according to the desired treatment and the location of the target neurons. In some embodiments the length of the ring electrodes  120  are less than or equal to the diameters of the ring electrodes  120 . In other embodiments, the lengths of the ring electrodes  120  are greater than the diameters of the ring electrodes  120 . 
     Deep brain stimulation leads may include one or more sets of segmented electrodes. Segmented electrodes may provide for superior current steering than ring electrodes because target structures in deep brain stimulation are not typically symmetric about the axis of the distal electrode array. Instead, a target may be located on one side of a plane running through the axis of the lead. Through the use of a radially segmented electrode array (“RSEA”), current steering can be performed not only along a length of the lead but also around a circumference of the lead. This provides precise three-dimensional targeting and delivery of the current stimulus to neural target tissue, while potentially avoiding stimulation of other tissue. Examples of leads with segmented electrodes include U.S. Pat. Nos. 8,295,944; and 8,391,985; and U.S. Patent Applications Publication Nos. 2011/0005069; 2010/0268298; 2011/0130817; 2011/0130818; 2011/0078900; 2011/0238129; 2011/0313500; 2012/0016378; 2012/0046710; 2012/0165911; 2012/0197375; 2012/0203316; 2012/0203320; and 2012/0203321, all of which are incorporated herein by reference. 
     In  FIG. 1 , the lead  100  is shown having a plurality of segmented electrodes  130 . Any number of segmented electrodes  130  may be disposed on the lead body  110  including, for example, one, two three, four, five, six, seven, eight, nine, ten, eleven, twelve, thirteen, fourteen, fifteen, sixteen or more segmented electrodes  130 . It will be understood that any number of segmented electrodes  130  may be disposed along the length of the lead body  110 . A segmented electrode  130  typically extends only 75%, 67%, 60%, 50%, 40%, 33%, 25%, 20%, 17%, 15%, or less around the circumference of the lead. 
     The segmented electrodes  130  may be grouped into sets of segmented electrodes, where each set is disposed around a circumference of the lead  100  at a particular longitudinal portion of the lead  100 . The lead  100  may have any number segmented electrodes  130  in a given set of segmented electrodes. The lead  100  may have one, two, three, four, five, six, seven, eight, or more segmented electrodes  130  in a given set. In at least some embodiments, each set of segmented electrodes  130  of the lead  100  contains the same number of segmented electrodes  130 . The segmented electrodes  130  disposed on the lead  100  may include a different number of electrodes than at least one other set of segmented electrodes  130  disposed on the lead  100 . 
     The segmented electrodes  130  may vary in size and shape. In some embodiments, the segmented electrodes  130  are all of the same size, shape, diameter, width or area or any combination thereof. In some embodiments, the segmented electrodes  130  of each circumferential set (or even all segmented electrodes disposed on the lead  100 ) may be identical in size and shape. 
     Each set of segmented electrodes  130  may be disposed around the circumference of the lead body  110  to form a substantially cylindrical shape around the lead body  110 . The spacing between individual electrodes of a given set of the segmented electrodes may be the same, or different from, the spacing between individual electrodes of another set of segmented electrodes on the lead  100 . In at least some embodiments, equal spaces, gaps or cutouts are disposed between each segmented electrode  130  around the circumference of the lead body  110 . In other embodiments, the spaces, gaps or cutouts between the segmented electrodes  130  may differ in size or shape. In other embodiments, the spaces, gaps, or cutouts between segmented electrodes  130  may be uniform for a particular set of the segmented electrodes  130 , or for all sets of the segmented electrodes  130 . The sets of segmented electrodes  130  may be positioned in irregular or regular intervals along a length the lead body  110 . 
     Conductor wires that attach to the ring electrodes  120  or segmented electrodes  130  extend along the lead body  110 . These conductor wires may extend through the material of the lead  100  or along one or more lumens defined by the lead  100 , or both. The conductor wires are presented at a connector (via terminals) for coupling of the electrodes  120 ,  130  to a control unit (not shown). 
     When the lead  100  includes both ring electrodes  120  and segmented electrodes  130 , the ring electrodes  120  and the segmented electrodes  130  may be arranged in any suitable configuration. For example, when the lead  100  includes two sets of ring electrodes  120  and two sets of segmented electrodes  130 , the ring electrodes  120  can flank the two sets of segmented electrodes  130  (see e.g.,  FIG. 1 ). Alternately, the two sets of ring electrodes  120  can be disposed proximal to the two sets of segmented electrodes  130  (see e.g.,  FIG. 3C ), or the two sets of ring electrodes  120  can be disposed distal to the two sets of segmented electrodes  130  (see e.g.,  FIG. 3D ). It will be understood that other configurations are possible as well (e.g., alternating ring and segmented electrodes, or the like). 
     By varying the location of the segmented electrodes  130 , different coverage of the target neurons may be selected. For example, the electrode arrangement of  FIG. 3C  may be useful if the physician anticipates that the neural target will be closer to a distal tip of the lead body  110 , while the electrode arrangement of  FIG. 3D  may be useful if the physician anticipates that the neural target will be closer to a proximal end of the lead body  110 . 
     Any combination of ring electrodes  120  and segmented electrodes  130  may be disposed on the lead  100 . For example, the lead may include a first ring electrode  120 , two sets of segmented electrodes; each set formed of four segmented electrodes  130 , and a final ring electrode  120  at the end of the lead. This configuration may simply be referred to as a 1-4-4-1 configuration. It may be useful to refer to the electrodes with this shorthand notation. Thus, the embodiment of  FIG. 3C  may be referred to as a 1-1-4-4 configuration, while the embodiment of  FIG. 3D  may be referred to as a 4-4-1-1 configuration. Other electrode configurations include, for example, a 2-2-2-2 configuration, where four sets of segmented electrodes are disposed on the lead, and a 4-4 configuration, where two sets of segmented electrodes, each having four segmented electrodes  130  are disposed on the lead. In some embodiments, the lead includes 16 electrodes. Possible configurations for a 16-electrode lead include, but are not limited to 4-4-4-4; 8-8; 3-3-3-3-3-1 (and all rearrangements of this configuration); and 2-2-2-2-2-2-2. 
       FIG. 2  is a schematic diagram to illustrate radial current steering along various electrode levels along the length of the lead  200 . While conventional lead configurations with ring electrodes are only able to steer current along the length of the lead (the z-axis), the segmented electrode configuration is capable of steering current in the x-axis, r-axis as well as the z-axis. Thus, the centroid of stimulation may be steered in any direction in the three-dimensional space surrounding the lead  200 . In some embodiments, the radial distance, r, and the angle θ around the circumference of the lead  200  may be dictated by the percentage of anodic current (recognizing that stimulation predominantly occurs near the cathode, although strong anodes may cause stimulation as well) introduced to each electrode. In at least some embodiments, the configuration of anodes and cathodes along the segmented electrodes allows the centroid of stimulation to be shifted to a variety of different locations along the lead  200 . 
     As can be appreciated from  FIG. 2 , the centroid of stimulation can be shifted at each level along the length of the lead  200 . The use of multiple sets of segmented electrodes at different levels along the length of the lead allows for three-dimensional current steering. In some embodiments, the sets of segmented electrodes are shifted collectively (i.e., the centroid of simulation is similar at each level along the length of the lead). In at least some other embodiments, each set of segmented electrodes is controlled independently. Each set of segmented electrodes may contain two, three, four, five, six, seven, eight or more segmented electrodes. It will be understood that different stimulation profiles may be produced by varying the number of segmented electrodes at each level. For example, when each set of segmented electrodes includes only two segmented electrodes, uniformly distributed gaps (inability to stimulate selectively) may be formed in the stimulation profile. In some embodiments, at least three segmented electrodes  230  in a set are utilized to allow for true 360° selectivity. 
     As previously indicated, the foregoing configurations may also be used while utilizing recording electrodes. In some embodiments, measurement devices coupled to the muscles or other tissues stimulated by the target neurons or a unit responsive to the patient or clinician can be coupled to the control unit or microdrive motor system. The measurement device, user, or clinician can indicate a response by the target muscles or other tissues to the stimulation or recording electrodes to further identify the target neurons and facilitate positioning of the stimulation electrodes. For example, if the target neurons are directed to a muscle experiencing tremors, a measurement device can be used to observe the muscle and indicate changes in tremor frequency or amplitude in response to stimulation of neurons. Alternatively, the patient or clinician may observe the muscle and provide feedback. 
     The reliability and durability of the lead will depend heavily on the design and method of manufacture. Fabrication techniques discussed below provide methods that can produce manufacturable and reliable leads. 
     Returning to  FIG. 1 , when the lead  100  includes a plurality of sets of segmented electrodes  130 , it may be desirable to form the lead  100  such that corresponding electrodes of different sets of segmented electrodes  130  are radially aligned with one another along the length of the lead  100  (see e.g., the segmented electrodes  130  shown in  FIG. 1 ). Radial alignment between corresponding electrodes of different sets of segmented electrodes  130  along the length of the lead  100  may reduce uncertainty as to the location or orientation between corresponding segmented electrodes of different sets of segmented electrodes. Accordingly, it may be beneficial to form electrode arrays such that corresponding electrodes of different sets of segmented electrodes along the length of the lead  100  are radially aligned with one another and do not radially shift in relation to one another during manufacturing of the lead  100 . 
     In other embodiments, individual electrodes in the two sets of segmented electrodes  130  are staggered (see.  FIG. 3B ) relative to one another along the length of the lead body  110 . In some cases, the staggered positioning of corresponding electrodes of different sets of segmented electrodes along the length of the lead  100  may be designed for a specific application. 
     Segmented electrodes can be used to tailor the stimulation region so that, instead of stimulating tissue around the circumference of the lead as would be achieved using a ring electrode, the stimulation region can be directionally targeted. In some instances, it is desirable to target a parallelepiped (or slab) region  250  that contains the electrodes of the lead  200 , as illustrated in  FIG. 2 . One arrangement for directing a stimulation field into a parallelepiped region uses segmented electrodes disposed on opposite sides of a lead. 
       FIGS. 3A-3D  illustrate leads  300  with segmented electrodes  330 , optional ring electrodes  320 , and a lead body  310 . The sets of segmented electrodes  330  include either two ( FIG. 3B ) or four ( FIGS. 3A .  3 C, and  3 D) or any other number of segmented electrodes including, for example, three, five, six, or more. 
     Any other suitable arrangements of segmented electrodes can be used. As an example, arrangements in which segmented electrodes are arranged helically with respect to each other. One embodiment includes a double helix. 
     One challenge to making leads with segmented electrodes is the correct placement of the electrodes, and retention of the desired electrode placement, during the manufacturing process. An electrode carrier can be utilized to hold the electrodes in the desired spatial arrangement during the manufacture of the lead. The electrode carrier is made of a non-conductive material to electrically isolate the segmented electrodes from each other and from the ring electrodes, if present. 
       FIG. 4  illustrates one embodiment of an electrode carrier  450 . The electrode carrier  450  includes a lattice region  452  that defines segmented electrode receiving openings  454  where the segmented electrodes are to be placed (see, for example,  FIG. 5 ). In the illustrated example, lattice region  452  of the electrode carrier  450  is designed for two sets of segmented electrodes with each set having three segmented electrodes. It will be recognized that other electrode carriers can be designed that include a different number of sets of segmented electrodes, a different number of segmented electrodes in a set, or a different spatial arrangement of the segmented electrodes (e.g., with sets staggered with respect to each other or with some or all of the segmented electrodes not arranged in sets), or any combination thereof. 
     The electrode carrier  450  may also include one or more tubular features  456  to receive a ring electrode (see, for example,  FIG. 5A ). The tubular features  456  may be provided on the proximal or distal ends (or both ends as illustrated in  FIG. 4 ) of the electrode carrier  450 . Alternatively or additionally, one or more tubular features can be provided at other locations on the electrode carrier if the ring electrode can be disposed around the tubular feature (for example, if the electrode has a “C” shape, or is a flexible strip, and can be wrapped, snapped, crimped, adhered, or otherwise disposed or fastened around the tubular feature.) In some embodiments, the distal-most ring electrode may be a tip electrode which has a closed end. Examples of a tip electrode can be found at, for example, U.S. patent application Ser. No. 13/906,776, incorporated herein by reference. 
     The electrode carrier  450  may also have a central lumen  458  through which conductors (see,  FIG. 5B ) attached to the segmented electrodes or ring electrodes can pass on the way to the remainder of the lead. The central lumen  458  may be open at both ends of the electrode carrier  450  or may be closed at the distal end of the electrode carrier. 
     The electrode carrier  450 , or at least the lattice region  452 , is formed of a non-conductive material which may be the same material as the lead body, for example, silicone, polyurethane, polyetheretherketone, or any other suitable biocompatible material. In some embodiments, the electrode carrier  450  may be made of a material that is stiffer or harder than the material of the lead body. For example, the material of the electrode carrier  450  may have a higher durometer than that of the lead body. In some embodiments, the electrode carrier  450  is made of the same type of polymer material (e.g., polyurethane or silicone) as the lead body, but with a higher durometer than the lead body. A stiffer or harder material for the electrode carrier may facilitate manufacturing. 
     Optionally, the electrode carrier  450  may be designed to allow a user to break the electrode carrier at predefined positions, such as one or more of breakage positions  460   a ,  460   b .  460   c . It will be understood that any of these positions, alone or in combination, may be selected for a breakage position or one or more other positions may be selected. The electrode carrier at the one or more breakage positions may be weakened. For example, the electrode carrier may have perforations, indentations, grooves, striations, or other arrangements that allow a user to break the carrier at the predefined positions. In at least some embodiments, breakage at these positions may occur, for example, after formation of the lead body or just prior to implantation. It will be understood that even if the breakage position is present in the electrode carrier, breakage of the electrode carrier does not necessarily occur. The breakage of the carrier at one or more breakage positions may reduce the stiffness of the lead at the distal end where the carrier resides. The stiffness of the carrier may be desirable during manufacture, but less desirable when the lead is implanted. 
       FIG. 5A  is an exploded view of an electrode carrier  550 , segmented electrodes  530 , ring electrodes  520 , and a portion of the lead  570 . The arrows in  FIG. 5A  indicate the places that the electrodes  520 ,  530  are attached onto the electrode carrier  550 . 
     The segmented electrodes  530  fit into the segmented electrode receiving openings  554  of the lattice portion  552  of the electrode carrier  550 . In some embodiments, the segmented electrodes  530  may form a friction fit with, or snap into, the lattice portion  552  surrounding the respective segmented electrode receiving openings  554 . In other embodiments, the segmented electrodes  530  may be held within the openings  554  merely by applying tension to conductors (see  FIG. 5B ) attached to the segmented electrodes. In some embodiments, adhesive or other fastening mechanisms may be used to hold the segmented electrodes in place once positioned. 
     The ring electrodes  530  fit onto the tubular features  556  of the electrode carrier  550 . In some embodiments, the ring electrodes  520  may form a friction fit with, or snap onto, the tubular features  556 . In other embodiments, the ring electrodes  520  may be held on the tubular features  556  merely by applying tension to conductors (see  FIG. 5B ) attached to the ring electrodes. In some embodiments, adhesive or other fastening mechanisms may be used to hold the ring electrodes in place once positioned. 
     In some embodiments, the other surface of the segmented electrodes  530  and the outer surface of the lattice portion  552  of the electrode carrier  550  may form an isodiametric arrangement when the segmented electrodes are nested in the segmented electrode receiving openings  554 . Optionally, the outer surface of the lattice portion  552  may also be isodiametric with the outer surface of the ring electrodes  520  when the ring electrodes  520  are seated on the tubular features  556  of the electrode carrier  550 . 
     In other embodiments, the outer surface of the lattice portion  552  may be recessed with respect to the outer surface of the segmented electrodes  552  when the segmented electrodes are nested in the segmented electrode receiving openings  554 . Optionally, the outer surface of the lattice portion  552  may also be recessed with respect to the outer surface of the ring electrodes  520  when the ring electrodes  520  are seated on the tubular features  556  of the electrode carrier  550 . Such arrangements may facilitate the formation of a portion of the lead body (for example, a jacket) between the segmented electrodes (and optionally between the ring electrodes and adjacent segmented electrodes) and over the lattice portion of the electrode carrier. 
     In some embodiments, the longitudinal length of one or more of the tubular features  556  is equal to the longitudinal length of the ring electrode  520  positioned thereon. In some embodiments, the longitudinal length of one or more of the tubular features  556  is less than the longitudinal length of the ring electrode  520  positioned thereon. This may facilitate attachment to a portion of the lead  570  to the electrode carrier and electrodes using the proximal-most ring electrode for attachment or may facilitate attachment of an end cap (not shown) using the distal-most ring electrode for attachment. In some embodiments, the longitudinal length of one or more of the tubular features  556  is greater than the longitudinal length of the ring electrode  520  positioned thereon. This may facilitate attachment to a portion of the lead  570  to the electrode carrier and electrodes using the proximal-most tubular feature for attachment or may facilitate attachment of an end cap (see.  FIG. 1  for lead with end cap distal to ring electrode) using the distal-most tubular feature for attachment. 
       FIG. 5B  illustrates one embodiment of a ring electrode  520  and a segmented electrode  530  each electrically coupled to a respective conductor  521 ,  531 . The conductors  521 ,  531  can be attached to the respective electrodes  520 ,  530  using any suitable method including, but not limited to, welding, soldering, adhesively attaching, or the like. Only these two electrodes are illustrated for clarity, but it will be understood that each of the other electrodes (see  FIG. 5A ) can be similarly attached to a conductor. 
     The conductor  521  is threaded through the central lumen  558  of the electrode carrier  550  to the portion of the lead  570 . The conductor  531  is threaded through the segmented electrode receiving opening  554  that is to receive the segmented electrode  530 . The conductor  531  proceeds through the central lumen  558  to the portion of the lead  570 . In some embodiments, the electrodes  520 ,  530  may be held on the electrode carrier  550  by applying tension to the conductors  521 ,  531  attached to the electrodes. It will be understood that the conductors  521 ,  531  can be attached to the electrodes  520 ,  530  prior to or after threading the conductors through the electrode carrier  550 . It will also be understood that the conductors  521 ,  531  can be attached to the electrodes  520 ,  530  prior to or after threading the conductors into the portion of the lead  570 . 
     The lead  570  may include a conductor tube  572  that carries the conductors through the lead to its proximal end. In the illustrated embodiment, the conductor tube  572  includes peripheral lumens  574  surrounding a central lumen  576 . Each of the peripheral lumens can carry one or more conductors and the central lumen can carry one or more conductors or may be useful as a stylet lumen. In some embodiments, each conductor  521 ,  531  is threaded through a different one of the peripheral lumens. 
       FIG. 5C  illustrated one embodiment of a lead  570  with the electrode carrier  550  disposed on the lead and the electrodes  520 ,  530  seated in the electrode carrier. In some embodiments, the electrode carrier  550  may form part of the exterior surface of the lead body. In other embodiments, a lead body may be formed over the electrode carrier (see.  FIG. 1 ). 
     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.