Patent Publication Number: US-8527054-B2

Title: Implantable medical device connector

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims benefit of copending U.S. Provisional Patent Application Ser. No. 61/221,953 entitled “Implantable Medical Device Header or Connector for Connecting Leads to a Power Source”, filed with the U.S. Patent and Trademark Office on Jun. 30, 2009 by the inventor herein; and is likewise based upon and claims benefit of copending U.S. Provisional Patent Application Ser. No. 61/226,393 entitled “Implantable Medical Device Header or Connector for Connecting Leads to a Power Source,” filed with the U.S. Patent and Trademark Office on Jul. 17, 2009; both of which specifications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of implantable medical devices, such as electrical stimulators, defibrillators, and pacemakers, and more particularly to a connector assembly for such devices configured to couple leads to the implantable device. 
     BACKGROUND OF THE INVENTION 
     Implantable medical devices (“IMD”) are used today for various applications to deliver electrical pulses from a pulse generator within the IMD, through an electrical lead connected to the IMD, to a targeted location within a patient&#39;s body. For instance, pacemakers are used to deliver electrical pulses generated within a pulse generator through an electrical lead to a patient&#39;s heart to maintain proper rhythm. In order to deliver those pulses, the electrical pulse from the generator is delivered through a lead connector assembly to a plurality of electrical contacts at one end of the lead, which lead then carries the electrical pulses to electrical contacts at the opposite end of the lead which are positioned adjacent the portion of the patient&#39;s heart that is to be stimulated. 
     Similarly, IMD&#39;s may be used in neurological applications, such as for deep-brain stimulation and spinal cord simulation, in which leads deliver electrical pulses generated in the IMD to targeted portions of a patient&#39;s brain or spinal cord. 
     In still other applications, leads may be used to sense particular conditions within a patient&#39;s body, and relay that sensed condition back to a processing unit within the IMD. 
     Many IMD&#39;s include a housing that houses the circuitry of the IMD, a connector block that connects the lead or leads to the IMD, and one or more leads inserted into the connector block to transfer electrical pulses generated within the IMD to the targeted portion of the patient&#39;s body. Many such connector blocks include female receptacles into which the male end of a multicontact lead may be inserted; however, the female receptacles are provided on only one end of the connector block. This configuration of the female receptacle of the header or connector may have a limiting effect on the number and types of leads that may be operated with a single implantable medical device. For instance, a connector block might have two receptacles, each providing 12 electrical contacts configured to receive a 12-contact lead. This configuration can be useful where the patient&#39;s condition requires the delivery of electrical stimulation using 12-contact leads, such as a 12-contact percutaneous electrode. If, however, the patient&#39;s condition changes such that an alternate configuration is desired (such as using 3 8-contact leads to more disparately apply the electrical pulses across a broader area), an alternative connector block must be provided that provides 3 8-contact receptacles. Requiring such a change of the IMD to receive an alternative lead configuration can be quite expensive and clearly uncomfortable and undesirable for the patient. Likewise, as doctors may have varied preferences for how and in what configuration electrical pulses should be delivered to a targeted portion of a patient&#39;s body (based on a particular patient&#39;s diagnosed condition), providing separate connector blocks for every possible configuration the doctor might come across can likewise become quite costly, as it significantly complicates the inventory that the doctor must maintain. 
     Therefore, it would be desirable to provide an improved connector block for an implantable medical device that could be variably configured to adapt to varied clinical conditions so as to allow the delivery of electrical pulses from an IMD in such varied clinical conditions using only a single, standard connector block. 
     Moreover, in some operative environments, operative space may be limited for inserting a lead longitudinally into the connector block on the IMD. In such environments, it would be desirable to provide an improved connector block that could allow insertion of leads into the connector block without requiring their longitudinal insertion, and that was otherwise configurable to minimize the amount of space that must be available in the operative environment to engage the leads with the connector block assembly. 
     SUMMARY OF THE INVENTION 
     Disclosed is an IMD including a connector block that allows varied lead configurations to be used with a single connector block and IMD assembly. The connector block is configured with one or more lead insertion lumens that are open at both ends, such that each end of the lead insertion lumen may receive a separate lead. The circuitry within the IMD is configured to allow the delivery of electrical pulses from a pulse generator within the IMD to two separate leads inserted within opposite ends of a single lead insertion lumen. 
     With regard to an aspect of a particularly preferred embodiment of the invention, a connector assembly for removably attaching a plurality of leads to an implantable medical device is disclosed, comprising a connector block housing having a first end and a second end, the connector block housing further comprising a lower casing and an upper casing removably attached to the lower casing, and at least one lead insertion lumen extending through the connector block housing from the first end to the second end and providing two points of entry through the connector block housing and into the lead insertion lumen, the lead insertion lumen further comprising a plurality of electrical contacts disposed within the lead insertion lumen and configured to direct an electrical pulse from a pulse generator assembly to a lead positioned within the lead insertion lumen. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying drawings in which: 
         FIG. 1  is an exploded perspective view of an implantable medical device in accordance with an exemplary embodiment of the present invention; 
         FIG. 2  is a front view of the implantable medical device of  FIG. 1 ; 
         FIG. 3  is a side view of the implantable medical device of  FIG. 1 ; 
         FIG. 4  is a perspective view of an application of the implantable medical device of  FIG. 1 ; and 
         FIG. 5  is a perspective view of a connector block according to one embodiment of the invention. 
         FIG. 6  is an exploded, perspective view of an implantable medical device having a modular connector block; 
         FIG. 7  is an exploded, perspective view of an implantable medical device having a modular connector block and an adapter within the connector block; and 
         FIG. 8  is an exploded, side view of an implantable medical device having a modular connector block and an adapter within the connector block. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of a particular embodiment of the invention, set out to enable one to practice an implementation of the invention, and is not intended to limit the preferred embodiment, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
     An IMD is described herein, such as an implantable pulse generator, which includes a connector block that allows varied lead configurations to be used with a single connector block and IMD assembly. The connector block has one or more insertion lumens extending through the connector block, providing two insert openings into which two separate leads may be inserted to separately receive electrical pulses from a pulse generator within the IMD. The pulse generator is preferably configurable so as to allow the delivery of appropriate pulses to the appropriate electrical contacts within the insertion lumen, thus allowing the intended stimulation signal to be transmitted through the intended leads and out to the stimulating contacts at the end of each such lead. Such configuration allows for varied lead configurations to be used with a single IMD, thus minimizing the need to maintain large inventories of varied connector block configurations and minimizing the extent of invasion into a patient&#39;s body if lead modifications must be made after the IMD has been implanted. 
     As shown generally in the exploded perspective view of  FIG. 1 , an exemplary embodiment of a biologically inert IMD  100  is shown including a pulse generator assembly  104  and a connector block  150  according to certain aspects of the present invention. In exemplary embodiments, connector block  150  receives the insertion ends of one or more leads  200  and  210 , thereby electrically connecting leads  200  and  210  with pulse generator assembly  104 , and in turn allowing an electrical pulse to pass from pulse generator assembly  104  to an electrode, a contact pad, or another connector in series, connected to the opposite end of each of the leads. 
     While  FIG. 1  particularly shows a connector block  150  in the form of a header which is joined to the body of a pulse generator, those of ordinary skill in the art will recognize that this illustrates only one possible configuration of the invention. Alternatively, a connector block embodying the invention could be joined to the end of an extension cable or lead(s), remote from the pulse generator. Any number of such connectors could be assembled in series, and by the variety of assembly arrangements which are possible, they could reconfigure or remap subsets of contacts and/or leads. 
     In the current embodiment, connector block  150  includes two insertion lumens  164  and  174  configured to receive leads  200  and  210  within either or, simultaneously, both open ends of a single insertion lumen. Insertion lumens  164  and  174  are configured to receive and removably hold the insertion ends of electrical leads  200  and  210  in a conventional manner, such as (by way of non-limiting example) a bal seal providing a physical and electrical connection to the multiple electrical contacts within each of insertion lumens  164  and  174  through a compressive contact, as are known to those of ordinary skill in the art. Those of ordinary skill in the art will also readily recognize that other mechanisms may likewise be used to mechanically hold leads  200  and  210  within insertion lumens  164  and  174  without departing from the spirit and scope of the instant invention, such as variously configured resilient, compression fit mechanisms, various snap-fit connection mechanisms, friction fit mechanisms, threaded connection mechanisms, and the like. As shown in the exemplary embodiment of  FIGS. 1-3 , a plurality of set screws  118  are provided to engage with the inserted end of the leads once they are positioned within the insertion lumens. Alternative secondary connector mechanisms that assist to ensure the secure connection of the lead within the insertion lumen may also be employed. For instance, various types of set pins and/or O-ring mechanisms may be employed. 
     Likewise, while only two insertion lumens are shown in the exemplary embodiment of  FIG. 1 , those of ordinary skill in the art will recognize that more or fewer insertion lumens may be provided in a connector block  150  without departing from the spirit and scope of the instant invention.
         In the exemplary embodiment of  FIG. 1 , each of insertion lumen  164  and insertion lumen  174  is provided first and second openings in connector block  150  configured to receive the proximal end of a lead, such as leads  200  and  210 . More particularly, the first insertion lumen  164  is provided a first opening  166  and a second opening  168 , with insertion lumen  164  extending through connector block  150  between first opening  166  and second opening  168 . Similarly, the second insertion lumen  174  is provided a first opening  176  and a second opening  178 , with insertion lumen  174  extending through connector block  150  between first opening  176  and second opening  178 . The first and second openings of the first and second insertion lumens may be variously sized and may be positioned at various locations within connector block  150 . Thus, each of the insertion lumens includes an open first end and an open second end, thereby establishing two open-ended insertion lumens within the body of the connector block  150 .       

     As shown in the exemplary embodiment of  FIG. 1 , each of connection lumens  164  and  174  extends the length and through the interior of connector block  150 . In the current embodiment, disposed along each of connection lumens  164  and  174  are a plurality of electrical contacts  192 . In the exemplary embodiment of  FIG. 1 , each of first and second connection lumens  164  and  174  contain 12 electrical contacts. In an alternative preferred embodiment, each connection lumen may include 24 contacts. As will be apparent to those of ordinary skill in the art, the number of contacts disposed in a connection lumen may vary from the foregoing as required for a particular application without departing from the spirit and scope of the invention. The configuration and dimensional characteristics of the electrical contacts within each connection lumen may vary to accommodate various technologies known to those skilled in the art. 
     In the exemplary embodiment of  FIG. 1 , connector block  150  is hermetically sealed to a housing  106 , which housing in turn contains pulse generator assembly  104 . The plurality of contacts  192  connect with circuitry of the pulse generator assembly  104  allowing the electrical stimulation to pass through to the plurality of contacts  192 . More particularly, pulse generator  104  preferably includes a power source and electronic circuitry configured to transmit electrical pulses to, for example, a plurality of pins  110  or other similarly configured electrical conductors capable of transmitting an electrical pulse to contacts  192  in the connection lumens. One end of pins  110  may connect with the electronic circuitry of pulse generator  104  in a manner that allows it to receive electrical pulses from the power source. The opposite end of pins  110  may allow for the transfer of electrical energy from the pulse generator assembly  104  to the contacts  192  within the insertion lumens. Further, the power source may include various types and configurations of batteries, various configurations of super-capacitors and such other power source technology that is known to those skilled in the art for producing an electrical impulse. In an exemplary embodiment, the power source employs a rechargeable or replenishable power source, such as a rechargeable battery or other replenishable power device. The particular type and configuration of the power source may vary as contemplated by those skilled in the art without departing from the scope and spirit of the current invention. 
     Those of ordinary skill in the art will also recognize that a wide variety of configurations may be used to electrically transmit electrical pulses from pulse generator  104  to electrical contacts  192  without departing from the spirit and scope of the invention, including (in the case where connector block  150  is not joined directly to pulse generator assembly  104 ) electrical cables or leads extending from pins  110 , or alternatively directly attaching to generator assembly  104 , that transmit the electrical pulses to a remotely located connector block  150 . Further, the connector block  150  may include an electrical connector plate that contacts the circuitry on one side and the contacts of the channel on the other side. It is further contemplated that the components may provide for or assist with the connection of the connector block  150  with the housing  106 . The use of various mechanisms that would further promote any of the above described features of the current invention and allow the implementation of the implantable medical device  100  in a manner similar to that described herein are contemplated for use. Further, as a variety of configurations are readily available and known to those of ordinary skill in the art for electrically communicating a pulse generator with electrical contacts within a connection lumen (such as those set forth in U.S. Patent Application Publication No. 2006/0167522, the specification of which is herein incorporated by reference), such assembly is not further detailed here. 
     The electronic circuitry of pulse generator  104  may preferably include a circuit board coupled to the power source and including various electronic components, which may include but are not limited to power circuits and a microcontroller. Such microcontroller is preferably capable of directing electrical pulses to specific pins  192  within each of connection lumen  164  and connection lumen  174 , and is likewise programmable (such as by way of a remote, handheld programmer communicating with telemetry circuitry in pulse generator  104 ) so as to store particular electrical pulse generation profiles for use depending on the lead configuration that is to be used with the IMD. Thus, by way of non-limiting example, in the case where a single 12-contact lead is to be used, the microcontroller of pulse generator  104  may be programmed to deliver electrical pulses appropriate for each of the contacts on such 12-contact lead. Likewise, where both an 8-contact lead and a 4-contact lead are to be used (each being inserted into an opposite end of the particular connection lumen), the microcontroller of pulse generator  104  may be programmed to deliver a first set of electrical pulses appropriate for the contacts of the 8-contact lead to eight of the contacts within the connection lumen, and to deliver a second set of electrical pulses appropriate for the contacts of the 4-contact lead to four of the contacts within the same connection lumen. Those of ordinary skill in the art will recognize that various other electrical pulse generation profiles may be desired for various patient conditions. 
     It is to be understood that connector block  150  described herein is exemplary and that various components, dimensional characteristics and/or configurations may be modified and still fall within the scope of the current invention. For instance, alternative embodiments may include a connector block with one insertion lumen or three or more insertion lumens disposed within the casing. 
     It is further contemplated that one or both ends of an insertion lumen may not have a lead inserted within it. Stops or plugs, such as plastic blanks, may be inserted into the opening of the unused end. Such plugs may be sized to complement, and facilitate precise insertion of, the lead. For example, a 12-contact insertion lumen may be provided with a plug at one end whose length occupies 4 contact positions, such that when an 8-contact lead is inserted so as to stop against the plug, it is at the correct depth. Alternatively, the length of the plug might occupy zero contacts, occluding only the end of the port, such as might be desirable for use with a 12-contact lead. 
     The insertion end of the leads are inserted through the insert openings of the insertion lumens in order to place contacts  220  on leads  200  and  210  in electrical communication with electrical contacts  192  within the insertion lumen. Overall, the configuration and dimensional characteristics of the insertion lumens can be varied as may be contemplated by those skilled in the art without departing from the spirit and scope of the current invention. 
     It is further contemplated that a connector block  150  may include two or more insertion lumens that are differently configured from one another. For example, the dimensional characteristics between the insertion lumens may vary. The number and configuration of electrical contacts within the insertion lumens may also vary. It is further contemplated that the connector block  150  may include, for instance, three insertion lumens where one of the insertion lumens is an open-ended insertion lumen as described above, and the other two insertion lumens include a closed second end. 
     The varying configurations available for the insertion lumens of the current invention allow leads of various configurations to be received and operationally coupled with a pulse generator assembly to transmit electrical stimulation provided by the implantable medical device to a desired portion of a patient&#39;s body. In the exemplary embodiment, and as particularly shown in  FIG. 1 , first leads  200  include an insertion end having a plurality of contacts  220 . Likewise, second leads  210  include an insertion end having a plurality of contacts  220 . By way of non-limiting example, there may be 8 contacts located on each of first leads  200 , and 4 contacts located on each of second leads  210 . In alternative embodiments, any of the leads may include 12 contacts, 8 contacts or various other numbers of contacts as may be required for a particular application.
         Those of ordinary skill in the art will recognize that in some instances, particular applications may warrant the use of four separate leads, which would correspond to the use of (again by way of non-limiting example) a 4×6 configuration (in which 4 leads are used, each having 6 electrical contacts) or, alternatively, a 2×4 configuration in combination with a 2×8 configuration (in which 4 leads are used, 2 having 4 electrical contacts and 2 having 8 electrical contacts). In order to simplify inventory, a lead manufacturer may desire to provide only 8-contact leads, in which case the connector block  150  may be configured to allow partial insertion (i.e., leaving two or four contacts exposed outside of connector block  150 ) if only 6 or 4 contacts are to be used. The order and number of the contacts at pulse generator  104  may, in turn, be programmed as detailed above to provide for such connection, such that the tip contact at the insertion end of the lead corresponds to the appropriate electrical contact  192  within the insertion lumen.       

     It may also be desirable in certain applications to provide for insertion of a lead into connector block  150  at varying depths so as to accommodate different lead designs by different manufacturers, again configuring the electrical contacts  192  within the respective insertion lumens to correspond to the appropriate contacts on such lead. As shown in  FIGS. 1-3 , set screws  118  may be provided at both ends of each of insertion lumens  164  and  174  to assist in holding such leads in place after insertion, whether partial or whole, into the respective insertion lumen. 
     Each of the insertion ends of leads  200  and  210  are inserted into the insert openings of the first or second ends of the first and second insertion lumens, respectively. As described above, the leads may be inserted simultaneously into both ends of a single insertion lumen. Once the insertion ends of leads  200  and  210  are fully inserted into their respective insertion lumens, the plurality of electrical contacts on those insertion ends of leads  200  and  210  are positioned in electrical communication with the plurality of contacts  192  contained within the respective insertion lumen. In the exemplary embodiment shown in  FIGS. 1-3 , the connector block  150  allows the simultaneous connection of four leads with the implantable medical device  100 , thereby further allowing electrical stimulation to be provided to all four leads simultaneously. 
     In an exemplary embodiment, the end of the lead opposite the insertion end can terminate in varying configurations, such as an in-line electrode or contact paddle that provides varying configurations of contacts for direct application of the electrical stimulation to a desired location, such as a particular location on or in a patient&#39;s body. In one embodiment, the contacts may be provided on a paddle in, for example, a 3×8 configuration (the 3×8 configuration is in reference to the number of columns and rows of individual contacts provided on the paddle). In this embodiment, the 24 contacts may be wired to two 12-contact insertion ends, which connect to two 12-contact insertion lumens on the connector block  150 . In a contemplated alternative embodiment, the contacts may be provided on three separate leads, each of which may be inserted and connected with connector block  150  independently; these may, by way of non-limiting example, be connected to the same two 12-contact insertion lumens by inserting two 4-contact leads (which may terminate in an 8-contact female connector) into one end of the two channels so as to accommodate one 8-contact lead extending from the paddle, while the other two leads are inserted into the other end of the two insertion lumens. 
     By way of further example, the configuration of the contacts on a paddle may alternatively be 4×6, or any other variety of electrode configurations. Still further, the contacts may alternatively comprise an in-line percutaneous electrode similar to a wire, wherein the conductive section extends in an integral manner from the rest of the lead. Various other configurations as contemplated by those of ordinary skill in the art may be employed without departing from the scope and spirit of the present invention. 
     Next, and with particularly reference to  FIG. 4 , so as to accommodate a variety of leads with different numbers of contacts and varying contact pad or in-line percutaneous electrode designs and configurations, adapters may be used with the current invention. For example, a “Y” cable adapter may be used having, for instance, an 8-contact male end and two 4-contact female ends, in which case the 8-contact male end may be inserted into one end of a single insertion lumen, with pulse generator  104  being programmed to deliver electrical pulses to the appropriate contacts on the 8-contact male end so as to transmit the intended electrical pulses to the separate 4-contact female ends, which in turn may separately transmit the received electrical pulses on to additional leads and/or connector blocks attached to the 4-contact female ends. Alternatively, and with regard to a particular aspect of the invention as shown in  FIG. 4 , a “Y” cable adapter  300  may be configured with two 4-contact male ends  310  which may be inserted into each of two insertion lumens of connector block  150 , while the opposite end of the “Y” cable adapter may terminate in an 8-contact female receptacle  320  configured to receive an 8-contact insertion end of a lead. In this novel configuration, the IMD could simultaneously support a total of three 8-contact percutaneous leads, which percutaneous leads could then be placed side-by-side to provide a minimally invasive tripole. Those of ordinary skill in the art will also recognize, however, that the adapter may include various numbers of contacts on either end without departing from the spirit and scope of the invention. In particularly preferred embodiments, the adapter  300  may be either rigid or semi-rigid, may be integrated tightly into the connector block  150 , or alternatively may be integrated with the outer body of pulse generator assembly  104 , such as by being coiled around a reel attached to the outer body of pulse generator assembly  104 , or removably housed within a shield or a bag  400  ( FIG. 4 ) attached to one side of the outer body of pulse generator assembly  104  within which redundant lead may be coiled. The operational use and connection scheme of the adapters may vary as contemplated by those skilled in the art and may allow any number of leads to be connected to a power source (described below) of the IMD  100  of the current invention. 
     In the exemplary embodiment shown in  FIGS. 1-3 , the pulse generator assembly  104  includes a housing  106 , otherwise commonly referred to as a “casing” or “can”. In one embodiment, the housing  106  may be integrally formed with the connector block  150 . Alternatively, connector block  150  may be connected with the housing  106  in a manner that allows the removal of the connector block  150 . Thus, similarly or differently configured housings  106  and connector blocks  150  may be interconnected with one another and fall within the scope of the current invention so long as at least one insertion lumen open at both ends is included within the connector block. Thus, the current invention contemplates that the configuration of the IMD  100  may be varied without departing from the spirit and scope of the invention. 
     Various connection mechanism(s) as contemplated by those skilled in the art may be employed by the current invention to allow the interchangeability of the housing  106  and connector block  150 . For example, a compression lock assembly may be employed where the connector block  150  may include a compressive device or receiver that connects with a receiver or compressive device included on the housing  106 . Other connection mechanisms, such as a snap-fit, friction-fit or otherwise known to those skilled in the art may likewise be employed by the current invention. Thus, it is contemplated that the positioning of the various components of the various connection mechanisms used to attach the connector block  150  to the housing  106  will be complimentary to one another. 
     Likewise, as shown in  FIG. 5 , connector block  150  may be provided as an entirely separate structure from a housing  106  and connected thereto via one or more electrical cables  310 . In this case, electrical cables  310  in one embodiment may provide an extended electrical connection between pulse generator assembly  104  within housing  106 , and contacts  192  in insertion lumens  164  and  174 , in which case electrical cables  310  may be directed into housing  106  to directly engage pulse generator assembly  104 . Alternatively, electrical cables  310  may terminate in leads configured for insertion into insertion lumens on an IMD header of traditional configuration. 
     With regard to an embodiment of the invention, and with particular reference to  FIG. 6 , a connector block  450  may alternatively be formed in a modular assembly including a lower casing  452  having a first insertion lumen  464  and a second insertion lumen  474  extending through casing  452 , wherein each of first insertion lumen  464  and second insertion lumen  474  have a plurality of electrical contacts  492  that again connect with circuitry of the pulse generator assembly  104  allowing the electrical stimulation to pass through to the plurality of electrical contacts  492 , all as described in greater detail above. However, each of first insertion lumen  464  and second insertion lumen  474  are formed as preferably half cylinders having an open top, thus allowing a lead to be laid or pressed down into the desired insertion lumen instead of requiring a longitudinal insertion of the lead into the insertion lumen. By allowing the lead to be so laid down into the channels formed by each of insertion lumen  464  and insertion lumen  474 , the operator may visually align the contacts  220  on a lead with the electrical contacts  492  in order to obtain the desired alignment (i.e., the desired longitudinal position of the lead  200  or  210  within the associated insertion lumen  464  or  474 ) without requiring the operator to guess as to alignment or to use a stop inserted in the opposite end of the respective insertion lumen. Once the operator has so laid the lead or leads in the desired insertion lumens  464  and/or  474 , an upper casing  454  may be placed on top of and tightly joined to lower casing  452  to seal the casings together, forming a closed, complete connector block  450 . Upper casing  454  may be configured as a cap, lid, membrane, or adhesive layer that seals and completes connector block  450 . Upper casing  454  may be joined to lower casing  452  in various manners to provide a completely sealed, biologically inert connector block  450 . For instance, and by way of non-limiting example, one or more threaded connectors  418  (e.g., a screw or bolt) may be inserted though one or more openings  417  in upper casing  454  and into threaded receivers  417  on lower casing  464  in order to removably attach upper casing  454  to lower casing  452 . Of course, those of ordinary skill in the art will recognize that other connector devices, such as compression locking mechanisms or friction fit locking mechanisms, may be used without departing from the spirit and scope of the invention. 
     Optionally, modular connector block  450  may include an adapter  500  configured to allow all leads that an operator desires to connect to a single pulse generator assembly  104  to extend from the connector block  450  in a single direction, rather than from opposite ends of the connector block  450 . Adapter  500  may including a casing  562  having a lead insertion lumen  564  extending therethrough (of similar configuration to lead insertion lumens  464  and  474 ). Lead insertion lumen  564  may, in turn, be provided a first set of electrical contacts  569  and a second set of electrical contacts  570 , each of which are configured to deliver an electrical pulse to a lead positioned within insertion lumen  564 . In order to electrically interconnect such electrical contacts  569  and  570  with the circuitry of pulse generator assembly  104 , each of the sets of electrical contacts  569  and  570  are in electrical communication with a lead connector assembly  510  comprising a first lead segment  510 A and a second lead segment  510 B of substantially identical configuration. One end of first lead segment  510 A is preferably in the form of a traditional electrical lead, having a plurality of contacts  513  situated along the terminating length of lead segment  510 A. The opposite end of first lead segment  510 A extends into casing  562 , and in turn establishes an electrical connection between contacts  513  and the first set of electrical contacts  569  in insertion lumen  564  via electrical conductors  514 . Similarly, one end of second lead segment  510 B is preferably in the form of a traditional electrical lead, having a plurality of contacts  517  situated along the terminating length of lead segment  510 B. The opposite end of second lead segment  510 B extends into casing  562 , and in turn establishes an electrical connection between contacts  517  and the second set of electrical contacts  570  in insertion lumen  564  via electrical conductors  518 . Each of lead segments  510 A and  510 B are configured for insertion into insertion lumens  464  and  474  of lower casing  452 , such that the contacts  513  and  517  of lead segments  510 A and  510 B, respectively, may be placed in contact with electrical contacts  492  of insertion lumens  464  and  474 . As a result, when pulse generator assembly  104  supplies an electrical pulse to the corresponding contacts  492  in insertion lumens  464  and  474 , that electrical pulse is in turn passed to lead segments  510 A and  510 B, and on to contacts  569  and  570  within insertion lumen  564  of adapter  500 . Those electrical pulses may, in turn, then be transferred to a lead positioned within insertion lumen  564 . With this configuration, if an operator wishes to deploy multiple leads, two of which have a number of contacts  220  less than the number of electrical contacts  492  in insertion lumens  464  and  474 , those leads may be placed in insertion lumens  464  and  474 , and the remaining electrical contacts  492  may be used to supply a third lead positioned in insertion lumen  564  in adapter  500 , thus allowing all of such leads to extend in the same direction from connector block  450 . This configuration may make removal, insertion, lead adjustment and/or replacement easier for a user of the device. 
     Alternatively, instead of electrically connecting electrical contacts  569  and  570  of insertion lumen  564  with electrical contacts  492  of insertion lumens  464  and  474  through the use of external lead segments  510 A and  510 B, direct, internal connections may optionally be provided. In this configuration, and with reference to  FIG. 8 , two rows of contacts  520  may extend outward from the bottom of adapter  500  and are preferably configured to sit within insertion lumens  464  and  474  of lower segment  452  of connector block  450  where they may be placed in electrical communication with electrical contacts  492 . Within adapter  500 , one row of contacts  520  is in electrical communication with the first set of electrical contacts  569  in insertion lumen  564  via electrical conductors  514 , while the other row of contacts  520  is in electrical communication with the second set of electrical contacts  570  in insertion lumen  564  via electrical conductors  518 . By providing such internally situated contacts  520 , the use of extraneous cabling associated with lead segments  510 A and  510 B may optionally be avoided, providing a more compact and potentially more easily manufactured connector block  450 . 
     As yet another alternative, while  FIG. 7  particularly shows adapter  500  configured as a separate layer sandwiched between lower casing  452  and upper casing  454 , those of ordinary skill in the art will recognize that first casing  452  could alternatively be configured with a third insertion lumen extending parallel to insertion lumens  464  and  474  and having internal electrical contacts wired in parallel with electrical contacts  492  in each of insertion lumens  464  and  474 . More particularly, one half of the electrical contacts in the third insertion lumen may be wired in parallel with four electrical contacts  492  in insertion lumen  464 , while the remaining half of the electrical contacts in the third insertion lumen may be wired in parallel with four electrical contacts  492  in insertion lumen  474 . Preferably, those contacts in insertion lumens  464  and  474  that are so wired to the electrical contacts in the third insertion lumen are contacts positioned at an end of each of the respective insertion lumens. In this case, and with regard to the particular exemplary configuration shown in  FIG. 7 , connector block  450  may optionally be used as either a 2×12 connector, or a 3×8 connector (in which case the two eight-contact leads in insertion lumens  464  and  474  do not engage the last four electrical contacts  492 , and a third eight-contact lead placed within the third insertion lumen will receive the electrical signal supplied by the pulse generator assembly  104  to the open electrical contacts  492  in insertion lumens  464  and  474 ), in each case with all leads extending from connector block  450  in a common direction. 
     Other than the modular, sandwich-type assembly of connector block  450 , all other features of connector block  450  are substantially identical to the features described above with respect to connector block  150  of  FIGS. 1-5 , including by way of non-limiting example the configuration of electrical contacts  492  within each of insertion lumens  464  and  474 , and the interconnection of such electrical contacts  492  with the circuitry of pulse generator assembly  104 , such that the discussion above regarding such features is equally applicable to the embodiments that comprise such modular, sandwich-type assembly of connector block  450 . 
     Moreover, those of ordinary skill in the art will recognize that the dimensions and configuration of the various components of the adapter  500  and of connector block  450  may be varied to accommodate the use of various different leads and/or header assemblies without departing from the spirit and scope of the invention. For instance, alternative embodiments may include an adapter  500  with multiple insertion lumens of various dimensions disposed within the casing. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.