Coupling module of a modular implantable medical device

0001The invention relates to medical devices, and more particularly, to implantable medical devices that deliver therapy to and/or monitor a patient.

0002The invention is directed to an implantable medical device that includes at least two modules, each of the modules comprising a housing. The IMD also includes a coupling module coupled to each of the modules. The coupling module defines at least one lumen between the modules and permits motion of the two modules along at least one axis of motion.

0003Depending on the application for which they are implanted in a patient, implantable medical devices (IMDs) may include a variety of electrical and/or mechanical components. Typically, an IMD includes a rigid housing that houses all of its components, which are generally fragile, to protect the components from forces to which they would otherwise be exposed when implanted within the human body. In order to avoid potentially harmful interactions between the components and bodily fluids, e.g., corrosion, IMD housings are typically hermetically sealed. Many IMD housings are fabricated from titanium because of its desirable rigidity and biocompatibility.

0004The size and shape of an IMD housing is dependant on the sizes and shapes of the components of the IMD. Large components common to most IMDs include a battery, a telemetry coil, and a hybrid circuit that includes digital circuits, e.g., integrated circuit chips and/or a microprocessor, and analog circuit components. Attempts have been made to reduce the size of the IMD housing by reducing the size of these components, changing the shape of these components, and organizing these components within the IMD housing to avoid empty space within the housing. Despite these efforts to reduce the size of IMD housings, the size, shape and rigidity of IMD housings still greatly limits the locations within the human body where an IMD can be practically implanted.

0005Due to these limitations, an IMD is typically implanted within the abdomen, upper pectoral region, or subclavicular region of a patient. Leads or catheters must be used in order to deliver therapy or monitor a physiological parameter at a location of the body other than where the IMD is implanted. Implantation and positioning of leads and catheters can be difficult and time-consuming from the perspective of a surgeon, particularly where the IMD is located a significant distance from the treatment or monitoring site. Moreover, the increased surgical time, increased surgical trauma, and increased amount of implanted material associated with the use of leads and catheters can increase the risk to the patient of complications associated with the implantation of an IMD.

0006For example, IMDs that are used to treat or monitor the brain, e.g., to deliver deep brain stimulation (DBS) therapy, are implanted some distance away from the brain, e.g., within the subclavicular region of patients. The long leads that connect the implantable medical device to electrodes implanted within the brain require tunneling under the scalp and the skin of the neck, thereby requiring increased surgery and a prolonged amount of time under general anesthesia during the implant procedure. The lengthy tract along the leads is more susceptible to infection, and the leads can erode the overlying scalp, forcing removal so that the scalp can heal. Further, the long leads running under the scalp and through the neck are more susceptible to fracture due to torsional and other forces caused by normal head and neck movements. Some references disclose medical devices for implantation within the head of a patient. For example, <patcit id="pcit0001" dnum="US6382281A"><text>US-A-6,382,281</text></patcit> discloses an implantable cochlear prosthesis. The prosthesis disclosed in this document includes pliable bridge connecting two hermetically sealed housing sections, and corrugated conductor lines that provide for future dimensional changes due to head growth. As another example, <patcit id="pcit0002" dnum="US6016449A"><text>US-A-6,016,449</text></patcit> discloses a multiple electrode, closed-loop, responsive system for the treatment of certain neurological diseases such as epilepsy, migraine headaches and Parkinson's disease. In one example, this document discloses that a flat coil used for telemetry or inductive power is located remotely from a control module of the implanted system. The flat coil is connected to the control module using wires. In addition, <patcit id="pcit0003" dnum="US6308101B"><text>US-B-6,308,101</text></patcit> discloses an implantable cochlear implant system including an implantable cochlear stimulator (ICS) unit that is connected to an implantable speech processor unit. The ICS unit has a coil permanently connected thereto through which magnetic or inductive coupling may occur with a similar coil located in the external headpiece during recharging, programming, or externally-controlled modes of operation. The ICS unit coil is located outside of the hermetic package of the ICS unit and two wires connect the coil to the hermetic package of the ICS unit. The present invention provides an implantable medical device as defined in claim 1 wherein the dependent claims relate to individual embodiments of the invention.

0007The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

0008<figref idref="f0001">FIGS. 1A and 1B</figref> are diagrams illustrating use of an implantable medical device in a patient.

0009<figref idref="f0002">FIG. 2</figref> is a schematic diagram illustrating another implantable medical device.

0010<figref idref="f0002">FIG. 3A and 3B</figref> are schematic diagrams illustrating another implantable medical device.

0011<figref idref="f0003">FIGS. 4A-4F</figref> are schematic diagrams illustrating various orientations of multiple modules within an implantable medical device.

0012<figref idref="f0004">FIG. 5A</figref> is a schematic diagram illustrating the construction of an overmold and modules used in construction of an implantable medical device.

0013<figref idref="f0004">FIG. 5B</figref> is an exploded view of an embodiment of the overmold and modules shown in <figref idref="f0004">FIG. 5A</figref>.

0014<figref idref="f0004">FIG. 5C</figref> is a side view of an embodiment of the overmold and modules shown in <figref idref="f0004">FIG. 5A</figref>.

0015<figref idref="f0005">FIGS. 6A-6C</figref> are schematic diagrams illustrating distributed modules and a coupling module with a single degree of freedom of motion.

0016<figref idref="f0006">FIGS. 7A-7B</figref> are schematic diagrams illustrating distributed modules having a one or more coupling modules with two degrees of freedom of motion.

0017<figref idref="f0007">FIG. 8</figref> is schematic diagram illustrating distributed modules having a coupling module with three degrees of freedom of motion.

0018<figref idref="f0007">FIG. 9</figref> is schematic diagram illustrating distributed modules having a coupling module having a hermetic and non-hermetic interconnection.

0019<figref idref="f0008 f0009">FIGS. 10A-10I</figref> are schematic diagrams illustrating exemplary shapes, configurations and features of a coupling module according to embodiments of the present invention.

0020<figref idref="f0010 f0011 f0012 f0013">FIGS. 11A-11M</figref> are schematic diagrams illustrating configurations of multiple modules and a coupling module according to embodiments of the present invention.

0021<figref idref="f0014">FIGS. 12A-12C</figref> are schematic diagrams illustrating module interfaces with a coupling module according to an embodiment of the present invention.

0022<figref idref="f0015">FIG. 13</figref> is a schematic diagram illustrating the axes of motion present in a multi-module implantable medical device.

0023<figref idref="f0015 f0016">FIGS. 14A-14C</figref> are a schematic diagrams illustrating motion restriction of a multi-module implantable medical device.

0024<figref idref="f0017">FIGS. 15A-15B</figref> are schematic diagrams illustrating the interaction of components of an implantable medical device that are part of an overmold.

0025<figref idref="f0018">FIGS. 16A-16B</figref> are a perspective diagrams illustrating a multi-module implantable medical device having an triangular module arrangement and a coupling module.

0026<figref idref="f0001">FIGS. 1A and 1B</figref> are diagrams illustrating use of an implantable medical device (IMD) in a patient. An IMD101 is implanted within a patient 100 in order to permit IMD 101 to provide therapies to the patient 100. In the example illustrated within <figref idref="f0001">FIGS. 1A-1B</figref>, IMD101 is implanted under the scalp of the patient 100 in order to locate the device 101 as close as possible to the location of leads 102 that provide the therapy.

0027<figref idref="f0001">FIG. 1A</figref> shows patient 100 with IMD 101 deployed beneath his scalp. In <figref idref="f0001">FIG. 1A</figref>, IMD 101 is a neurostimulator that provides deep brain stimulation via leads 102 deployed in the brain of patient 100. IMD 101 is deployed in proximity to site of stimulation therapy. IMD 101 may be used to treat any nervous system disorder including, but not limited to, epilepsy, pain, psychological disorders including mood and anxiety disorders, movement disorders (MVD) such as, but not limited to, essential tremor and Parkinson's disease and neurodegenerative disorders.

0028Although IMD 101 is depicted as a neurostimulator, the invention is not limited to applications in which the IMD is a neurostimulator. The invention may be employed with IMDs that perform any monitoring or therapeutic functions. The invention is not limited to IMDs that include leads deployed in the brain, but may also be employed with leads deployed anywhere in the head or neck including, for example, leads deployed on or near the surface of the skull, leads deployed beneath the skull such as near or on the dura mater, leads placed adjacent cranial or other nerves in the neck or head, or leads placed directly on the surface of the brain. Nor is the invention limited to IMDs that are coupled to electrodes. The invention may be employed with IMDs coupled to any sensing or therapeutic elements, such as temperature sensors or motion sensors. The invention may also be employed with different types of IMDs including, but not limited to, IMDs operating in an open loop mode (also referred to as non-responsive operation), IMDs operating in a closed loop mode (also referred to as responsive), and IMDs for providing monitoring and/or warning.

0029In general, IMD 101 has a low profile, i.e., IMD 101 is thin to permit IMD 101 to be deployed effectively, comfortably and cosmetically and under the scalp. In one embodiment of the invention, IMD 101 has a maximum thickness of between approximately 4 millimeters and approximately 8 millimeters. The use of a reduced profile may reduce the risk of infection, skin erosion and cosmetic issued related to the implantation of IMD 101.

0030Many locations within a patient do not present adequate profile for implantable medical devices. As such, many uses of such devices employ lengthy leads located remote from an implantation site of the IMD. The use of these lengthy leads requires complicated insertion procedures from the site of the IMD to the site of lead deployment that may cause medical complications to the patient as well as may lead to failures in connection leads. By constructing IMD 101 as a set of distributed modules connected together as described herein, IMD 101 may be deployed proximate to a treatment or monitoring site.

0031While the IMD 101 shown in <figref idref="f0001">FIGS. 1A-1B</figref> is implanted under the scalp of patient 100 and may be used when the therapy provided to patient 100 includes neural stimulation of a brain, other embodiments of IMD 100 permit the device to be implanted at many other locations within the body. In addition, IMD 101 includes a plurality of interconnected modules. Each module generally perform assigned functions.

0032In the typical embodiment depicted in <figref idref="f0001">FIG. 1B</figref>, IMD 101 includes three modules, namely, a control module 103, a power supply module 104 and a recharge module 105. Control module 103 typically includes the electronic components associated with the functions of IMD 101. In a typical implementation, control module 103 may include a hybrid circuit that includes digital circuits such as integrated circuit chips and one or more microprocessors, and analog circuit components. Accordingly, control module 103 may also be referred to as an electronic module. Power supply module 104 typically comprises one or more energy storage devices, such as a rechargeable lithium ion battery. Recharge module 105 typically includes one or more coils for transmitting or receiving electromagnetic energy through the scalp. The transmitted energy may include energy to be stored in power supply module 104. In some embodiments, the transmitted energy may also include communication, such as information encoded in radio frequency transmissions.

0033Individual modules 103 and 104 may be encased in biocompatible metal shields such as titanium shield halves, and may be sealed against contamination. In addition, individual modules 103 and 104 may include insulation to electrically isolate the electrical components inside the modules from the metal shields. The modules are coupled to an overmold 106 which may be made of a biocompatible material. Use of the term "overmold" herein is not intend to limit the invention to embodiments in which the overmold is a molded structure. Overmold may be a molded structure, or may be a structure formed by any process. In addition, one or more coupling modules (not shown in <figref idref="f0001">FIG. 1A</figref>) may couple one or more modules to one another.

0034In some embodiments of the invention, overmold 106 encases all modules 103, 104 and 105. In other embodiments, overmold 106 is disposed over or around the modules without encasing the modules. In further embodiments, overmold 106 acts as a "frame" to hold the modules in a fixed position relative to one another, but does not fully cover the modules. Some features of the overmold, and variations on the shape of the overmold, are presented below. In general, the shape of the overmold depends upon the arrangement of the modules. The overmold may be made of a variety of materials, such as flexible silicone. The overmold may also include a rigid polymer such as Ticothane surrounded by flexible silicone. The invention is not limited to these materials, however, and the overmold may comprise any combination of elastomeric and/or non-elastomeric materials.

0035<figref idref="f0002">FIG. 2</figref> is a schematic diagram illustrating an IMD 201. In this example, IMD 201 is arranged in a triangular configuration. IMD 201 includes three separate modules: a control module 210, a power source module 211, and a recharge module 212. These three modules are connected together to construct IMD 201. IMD 201 also contains a set of lead connection elements 213 that permit external leads to be connected to the control module 210 as needed. The triangular configuration of IMD 201 permit IMD 201 to possess a thin profile by spreading the modules over a larger surface area. In order to minimize the surface area compact, a triangular configuration is used. The configuration of IMD 201 may also be manipulated to conform to the shape of the location within a patient in which the device is being implanted. For example, implantation of IMD 201 under the scalp of a patient may be accomplished if the overall shape of IMD 201 is curved to follow the shape of a patient's skull. Any number of shapes may be used to match a particular IMD 201 to an implantation location for a device.

0036<figref idref="f0002">FIG. 3A and 3B</figref> are schematic diagrams illustrating an IMD 301. In this IMD 301, a flat device is shown that consists of multiple modules. This embodiment may be used in other locations within a patient in which the implantation location does not require such an exact match between the device and physical structures of the patient such as bone or muscle. IMD 301 may still be a modular device consisting of multiple modules as IMD 301 may provide a smaller profile when implanted as to not protrude excessively once implanted. IMD 301 need not be rigid, and in some embodiments the orientation of the modules of IMD 310 may change relative to one another.

0037The flat embodiment shown in <figref idref="f0002">FIGS. 3A-3B</figref> may represent a device that may be a pectoral implant that may be used to treat angina, to provide vagal nerve stimulation, or to provide cardiac rhythm management. Similar devices may be implanted into an upper buttock implant location, into an abdomen location, and into periphery. A device implanted into an upper buttock location may be useful in a configuration for urological and gastrological implantation therapies. A device implanted into an abdomen location may be useful a configuration for providing pain, spasticity, and chemotherapy treatment. A device implanted into a periphery location may be useful a configuration for providing muscle stimulation, on-site nerve stimulation, and diaphragm stimulation therapies. These devices may both provide therapies as well as provide a platform for sensing conditions present within a patient.

0038Additional alternate embodiments for implantable medical devices implemented according to principles of the present invention may also include non-electrical based therapies such as targeted introduction of fluids and similar therapeutic agents using pumps and reservoirs.

0039<figref idref="f0003">FIGS. 4A-4F</figref> are schematic diagrams illustrating exemplary configurations and orientations of modules within IMD 401 A through 401F (hereinafter 410). IMD 401 consists of multiple modules that may be arranged into any number of orientations as shown in the various embodiments of <figref idref="f0003">FIGS. 4A-4F</figref>. For reference, each IMD 401 is depicted deployed proximate to the skull of a patient, with leads 402A and 402B deployed through burr holes 402A and 402B and coupled to IMD 401. The leads are coupled to the IMD via lead connection modules 415A and 415B. As shown in <figref idref="f0003">FIGS. 4A-4F</figref>, the lead connection modules may assume a variety of orientations relative to other components of IMD 401.

0040In each of these embodiments, IMD 401 has three modules as discussed above in reference to <figref idref="f0001">FIGS. 1B</figref> and <figref idref="f0002">2</figref>: a control module 410, a power source module 411, and a recharge module 412. An overmold 413 at least partially covers the housings of control module 410 and power source module 411. The modules may be arranged into a number of orientations as long as any interconnections between the modules may be routed within the device. The various embodiments include triangular configurations, as is shown in <figref idref="f0003">FIGS. 4A-4C</figref>, or linear configurations as shown in <figref idref="f0003">FIGS. 4D-4F</figref>. In <figref idref="f0003">FIG. 4D</figref>, one of the three modules, such as the recharge module, is deployed as a tethered module 414 rather than being covered by overmold 413.

0041The invention is not limited to the deployments of the lead connection modules shown in <figref idref="f0003">FIGS. 4A-4F</figref>. The lead connection modules may be located on various positions within IMD 401. Lead connection modules may be oriented, for example, to permit the leads to be routed to lead locations in an efficient manner or to support management of excess lead length. Any number of other orientations and alternate embodiments may be constructed according to principles of the present invention and consistent with the claims recited herein.

0042In each of the exemplary embodiments depicted in <figref idref="f0003">FIGS. 4A-4F</figref>, any two modules may be interconnected via one or more coupling modules (not shown in <figref idref="f0003">FIGS. 4A-4F</figref>). The particular coupling modules may depend upon the number of modules, the distance of the modules from one another, the amount of motion or displacement of one module from another, the expected direction or directions of displacement, whether the modules are arranged in a triangular, linear or other configuration, and so on.

0043<figref idref="f0004">FIGS. 5A-5C</figref> are schematic diagrams illustrating an exemplary construction of an overmold used in construction of an IMD according to the present invention. <figref idref="f0004">FIG. 5A</figref> illustrates that IMD 501 comprises a set of modules 510-512, a set of motion restriction elements, such as motion restriction fibers 521. In <figref idref="f0004">FIG. 5A</figref>, motion restriction fibers 521 are coupled to modules 510 and 511, and are covered at least in part by overmold 522. Overmold 522 typically includes a solid biocompatible material. Overmold 522 may comprise an elastomeric material that is soft and flexible, such as silicone. In addition or in the alternative, overmold 522 may comprise a non-elastomeric material that imparts rigidity to IMD 501. In one embodiment, for example, a non-elastomeric material in overmold 522 acts as a "frame" to hold the modules in a fixed position relative to one another, and does not fully cover the modules. Overmold 522 covers, at least in part, the components and modules within IMD 501 while providing a flexible structure that permits the device 501 to conform to fit each individual patient. Because overmold 522 is typically flexible, IMD 501 may benefit from motion restriction devices such as motion restriction fibers 521, which provide structural integrity to device 501 once implanted into the patient.

0044<figref idref="f0004">FIG. 5B</figref> illustrates that the overmold 522 may include a non-elastomeric, or "hard" component 531 in addition to an elastomeric, or "soft" component 532. In <figref idref="f0004">FIG. 5B</figref>, the non-elastomeric component 531 is shaped to conform to the shape of at least one of modules 510-512 such that the modules may be restrained from motion by the non-elastomeric components. The non-elastomeric components 531 are typically made of a solid biocompatible material such as polysulfone, and may also be made of metal such as titanium.

0045The non-elastomeric components 531 are utilized in locations in which motion is to be restricted. Any or all modules may be constrained by one or more hard components 531. Overmold 522, including elastomeric and non-elastomeric components, can be fabricated into a single structure before the modules 510-512 are inserted into the device 501.

0046Generally, overmold 522 serves a number of functions. For example, overmold 522 incorporates motion restriction elements within the device 501, and attaches to modules and other elements to provide a unified device. In addition, overmold 522 provides a smooth interface surface for the device as it interacts with the patient, and protects electrical connections and feed through wires that connect modules to external leads.

0047Overmold 522 may also include a durometric specific material to provide desired device qualities such as flexibility and structural integrity. In addition, the material used to construct overmold 522 may possess a thermal conductivity characteristic to either act as a heat sink, or act as an insulator to shield the patient 100 from any excess heat from IMD 501. Because IMD 501 may be constructed from a large number of modules to perform a desired task, the materials selected for used in constructing the overmold 522 may vary as needed by each embodiment.

0048<figref idref="f0004">FIG. 5C</figref> illustrates that overmold 522 provides sloped interface 541 between an exemplary module 542 within IMD 501 and the patient's body. In embodiments in which IMD 501 is implanted within tight spaces, such as under the scalp of the patient, sloped interface 541 provides a smooth transition and eases sharp edges that are known to cause possible points of stress for tissue. An angle of interface from the patient's body and the sloped interface 541 can be approximately 135 degrees.

0049In the exemplary embodiments depicted in <figref idref="f0004">FIGS. 5A-5C</figref>, any two modules may be interconnected via one or more coupling modules (not shown in <figref idref="f0004">FIGS. 5A-5C</figref>). In addition to considerations identified above, the particular coupling modules may depend upon the configuration of the overmold, the configuration of elastomeric and non-elastomeric components; the presence of motion restriction devices, and so on.

0050<figref idref="f0005">FIGS. 6A-6C</figref> are schematic diagrams illustrating two distributed modules 610, 611 having a coupling module 612. In <figref idref="f0005">FIGS. 6A-6C</figref>, coupling module 612 provides a single degree of freedom to move. In particular, coupling module 612 limits motion of modules 610, 611 relative to one another to a single axis.

0051IMD 601 shown in this embodiment is constructed from two individual modules 610-611 that are physically linked using a flexible coupling module 612 that may also be referred to as a "power pipe module." This coupling module possesses a coupling body having a connection end at each connection interface with a module. In a typical implementation, a coupling module 612 interfaces with a module by being coupled to a housing of the module. In each of the three embodiments shown in <figref idref="f0005">FIGS. 6A-6C</figref>, coupling module 612 constrains translational motion of one module relative to another. In <figref idref="f0005">FIGS. 6A-6C</figref>, coupling module 612 includes a flexible zone that is bendable.

0052In <figref idref="f0005">FIGS. 6A-6C</figref>, coupling module 612 is generally narrower than the dimensions of the modules 610-611. Furthermore, coupling module 612 may be constructed of a more flexible material than the modules, resulting in some freedom of bending. In <figref idref="f0005">FIG. 6A</figref>, coupling module 612 is depicted as a distinct module coupled to two modules. In <figref idref="f0005">FIGS. 6B and 6C</figref>, by contrast, coupling module 612 forms part of a unified structure with modules 610 and 611. <figref idref="f0005">FIG. 6B</figref> illustrates the coupling module 612 as including a narrow zone between two compartments of a common structure, with a module deployed within each of the two compartments 610-611. <figref idref="f0005">FIG. 6C</figref> shows the coupling module 612 as including a distinctly separate ribbed element that separates the two modules 610-611 and that accommodates some motion of the modules relative to one another.

0053With the freedom provided by coupling module 612, modules 610-611 may be oriented relative to one another, such that IMD 601 as a whole includes a convex surface. Coupling module 612 may be semi-rigid to permit the IMD 601 to be manipulated into a desired shape and then retain modules 610-611 in a desired orientation. Alternatively, coupling module 612 may flexibly permit modules 610-611 to move freely about an axis of rotation 613.

0054Coupling module 612 defines at least one lumen or passageway. This lumen (not shown in <figref idref="f0005">FIGS. 6A-6C</figref>) permits components and elements in one module 610 to be mechanically or electrically coupled to other components and elements in the other module 611. Coupling module 612 provides a structural support element that protects these connections between modules from damage. Coupling module 612 may also include one or more hermetic interfaces between a module and coupling module 612 to environmentally protect the modules 610-611 from contamination. In some embodiments, coupling module 612 is hermetically fixed to at least one of the housings of modules 610-611. In other embodiments of the invention, coupling module 612 may be fixed to one or more modules non-hermetically.

0055<figref idref="f0006">FIGS. 7A-7B</figref> are schematic diagrams illustrating two distributed modules having a coupling module with at least two degrees of freedom to move. IMD 701 shown in these embodiments includes two modules 710-711 that are physically linked using a coupling module 721 that may typically possess two degrees of motion. In each of the three exemplary embodiments shown in <figref idref="f0006">FIGS. 7A-7C</figref>, a flexible coupling module 721 exists between the two modules 711-712.

0056In these embodiments, the flexible coupling module 721 may flex about two axis of rotation that correspond to dimensions of the of coupling module 721 that are most narrow. Coupling module 721 may rotate in a pitch and yaw axis, for example, but not in a roll axis.

0057In <figref idref="f0006">FIG. 7B</figref>, IMD 701 includes a third module 713 coupled to another module 711 via a second coupling module 722. Coupling module 722, like coupling module 721, may support two axes of motion. As a result, the individual modules 711, 712, 713 may be oriented relative to one another in three dimensions. Coupling module 722, like coupling module 721, may be hermetic or non-hermetic. Coupling modules 721 and 722 may have, but need not have, comparable degrees of flexibility.

0058<figref idref="f0007">FIG. 8</figref> is schematic diagram illustrating an IMD 801 having two distributed modules 811, 812 with a coupling module 821 that affords three degrees of freedom to move, according to an embodiment of the present invention. In <figref idref="f0007">FIG. 8</figref>, modules 811-812 are physically linked with coupling module 821. Coupling module 821 affords some freedom to orient modules 811-812 so that modules 811-812 are not co-planar. Modules 811 and 812, may be moved closer or farther apart by flexing coupling module 821 at bend 831A or bend 831B, or both. Modules 811 and 812, may also be twisted relative to one another by bending or twisting elongated section 832. In the embodiment shown in <figref idref="f0007">FIG. 8</figref>, module 811 includes a notched connection point 833 that enables an enhanced range of motion.

0059The degree of motion is a function of the configuration of the coupling module, such its length or the number and placement of bends, and the material from which the coupling module is constructed. In one embodiment, the coupling module is formed of titanium. Other metals such as stainless steel may also be used to construct the coupling module. Moreover, a coupling module may be constructed from more than one material. In general, a coupling module should be durable and reliable, and should be subject to bending or twisting without damage.

0060<figref idref="f0007">FIG. 9</figref> is schematic diagram illustrating an IMD 901 with two distributed modules 911 and 912 and a coupling module 921 having both a non-hermetic boundary 931 and a hermetic boundary 932. In this embodiment,the boundary between module 911 and coupling module 921 is non-hermetic. In contrast, the boundary between module 912 and coupling module 921 is hermetic. Such an arrangement may make the fabrication of IMD 901 simpler as it eliminates a hermetic interconnection boundary that imposes cost, complexity and size limitations. In some circumstances, hermetic sealing of module components is unnecessary.

0061The nature of the hermetic interfaces above described refer to the interfaces between modules and the coupling modules. As such, the overall device 901 may possess no hermetic interfaces between these modules, and may permit passage of liquid or gaseous material between modules, while the entire structure of IMD 901 remains hermetically sealed from the patient. In another embodiment, one module, such as a non-hermetic battery may be enclosed within a hermetically sealed module that does not permit battery material to pass into a coupling module and any other modules. In this embodiment, the entire device 901 may also be hermetically sealed from the patient. In a third embodiment, the various interfaces between all modules and a particular coupling module may possess hermetic interfaces while the coupling module itself is not hermetically sealed to the patient. As such, a coupling module containing an AC power connection between modules may not require a hermetically sealed coupling module with respect to the patient.

0062In addition, the lumen defined by coupling module 921 need not be empty or filled with air. In some embodiments, coupling module 921 may be back filled with fluids and other materials. Such materials may, for example, offer some isolation of components disposed in the coupling module, or may insulate, or may dissipate heat, or may absorb gases that may be emitted by a battery in a power supply module.

0063<figref idref="f0008 f0009">FIGS. 10A-10I</figref> are schematic diagrams illustrating exemplary coupling module shapes and configurations according to embodiments of the present invention. Coupling module 1001 provides a protected interconnection volume between two modules within a modular IMD. The particular shape for the coupling module 1001 may be affected by the nature of the interconnection between the two modules, the orientation of the modules, the size of the lumen, the desired degree of flexibility, and the like. One generally desirable characteristic of the coupling module is that it be flexible enough to accommodate some motion of the modules relative to one another without becoming damaged. Some embodiments of coupling module 1001 may also provide structural protection and support for the module interconnection.

0064<figref idref="f0008">FIGS. 10A-10C</figref> illustrate a coupling module 1001 having a single lumen connecting two modules. <figref idref="f0008">FIG. 10A</figref> illustrates a round or circular lumen. <figref idref="f0008">FIG. 10B</figref> illustrates a semi- circular lumen. <figref idref="f0008">FIG. 10C</figref> illustrates a rectangular lumen. The invention is not limited to a lumen having any particular cross-section, and includes coupling modules having cross-sections not specifically shown herein.

0065<figref idref="f0008">FIG. 10D</figref> illustrates a coupling module 1001 that possesses a bellows section 1002 as part of its structure. Bellows 1002 enhances the flexibility of coupling module 1001. In particular, the embodiment of coupling module 1001 depicted in <figref idref="f0008">FIG. 10D</figref> illustrates a coupling module that includes variations in the cross-sectional diameter that accommodate motion along one or more axes of motion. The bellows configuration in <figref idref="f0008">FIG. 10D</figref> is illustrative, and the invention includes embodiments that comprise corrugations, convolutions, or other variations in cross-sectional shape that impart degrees of freedom of movement.

0066<figref idref="f0009">FIG. 10E</figref> illustrates that a coupling module 1001 of any configuration discussed herein may include multiple lumens. The lumens may provide independent interconnection paths that are separate from each other. These multiple lumens permit the coupling module to provide connections that are isolated from one other. In <figref idref="f0009">FIG. 10E</figref>, lumens 1003A and 1003B are side-by-side. <figref idref="f0009">FIG. 10F</figref> illustrates a coupling module 1001having coaxial lumens. In <figref idref="f0009">FIG. 10F</figref>, the lumens include an inner conductor 1004A and an outer conductor 1004B separated from inner conductor 1004A by a dielectric 1005, such that coupling module is similar to a coaxial cable. In some embodiments, the lumens of a coaxial coupling module need not include conductors or dielectrics. The invention encompasses embodiments in which lumens are configured in a concentric fashion.

0067<figref idref="f0009">FIG. 10G</figref> illustrates a coupling module 1001 that is a ring-like structure having a plurality of separate conduit segments around the ring. <figref idref="f0009">FIG. 10H</figref> illustrates another concentric arrangement for conduits in which an inner conduit 1010 is separated from an outer conduit 1011. Finally, <figref idref="f0009">FIG. 10I</figref> illustrates that a coupling module may be arranged to include a helix-like structure. A helix-like structure may, for example, tend to permit more motion along some axes and less motion along others.

0068In some embodiments of the invention, a coupling module may include a combination of features shown in <figref idref="f0008 f0009">FIGS. 10A-10I</figref>. For example, a coupling module may include a straight portion and a helical portion, or multiple lumens and a bellows section. The invention encompasses all of these combinations.

0069<figref idref="f0010 f0011 f0012 f0013">FIGS. 11A-11M</figref> are schematic diagrams illustrating configurations of multiple modules having a coupling module interconnecting two modules according to embodiments of the present invention. <figref idref="f0010 f0011 f0012 f0013">FIGS. 11A-11M</figref> illustrate various arrangements of interconnected modules used to construct an IMD. These arrangements illustrate some of arrangements for in-line and triangular configurations of the modules. These arrangements illustrate use straight and helix-like arrangements of the coupling modules. Finally, these arrangements illustrate interconnection of modules from adjacent module surfaces or sides as well as interconnection of non-adjacent sides of modules.

0070Combination of various features gives rise to the exemplary arrangements shown in <figref idref="f0010 f0011 f0012">FIGS. 11A-11H</figref>. In particular, coupling module 1101 may include a combination of straight, curved or helical sections when coupling module 1110 to module 1111. <figref idref="f0012">FIGS. 11I and 11J</figref> illustrate more rigid coupling module 1101 arrangements between adjacent sides of two modules 1110-1111. <figref idref="f0013">FIG. 11K</figref> illustrates that a coupling module 1101 may connect two modules 1110-1111 by bending around a third module 1112. Finally, <figref idref="f0013">FIGS. 11L-11M</figref> illustrate the interconnection of two modules 1110-1111 using an S-shaped coupling module 1101. Embodiments in <figref idref="f0013">FIGS. 11L-11M</figref> include any arrangement and shape for a connection body used to construct a coupling module possessing at least one nonlinear bend.

0071<figref idref="f0014">FIGS. 12A-12C</figref> are schematic diagrams illustrating module interfaces with a coupling module according to an embodiment of the present invention. <figref idref="f0014">FIGS. 12A-12B</figref> illustrate construction of two distributed modules from case components 1201-1202, module end caps 1211-1212, and a flexible interconnection coupling module 1222. The module end caps 1211-1212, and a flexible interconnection coupling module 1222 are mechanically coupled using weld joints 1231-1232. The module end caps 1211-1212 may be coupled to case components 1201-1202 with welds or braze joints. As is discussed above, these connections mat be either hermetic, as shown, or non-hermetic. <figref idref="f0014">FIG. 12C</figref> illustrates a completed module end cap and coupling module assembly 1241 that may be further coupled to two modules (not shown) to construct a modular IMD.

0072<figref idref="f0015">FIG. 13</figref> is a schematic diagram illustrating the degrees of motion present in a multi-module IMD. For any two modules within a modular medical device, motion between the two devices may be defined in terms of pitch motion 1301 (shown in side view), yaw motion 1302 (shown in top view), and roll motion 1303 (shown in end view). For the set of motion restriction elements (not shown) discussed above, all three degrees of motion may be limited to prevent mechanical failures of interconnections between the modules during use of an IMD.

0073<figref idref="f0015 f0016">FIGS. 14A-14C</figref> are a schematic diagrams illustrating motion restriction within various degrees of motion within a multi-module IMD. For any two modules 1401-1402 within an IMD, motion restriction elements 1422-1423 may be employed to constrain the relative orientation of modules 1401-1402. Motion restriction elements 1422-1423 may be sufficient to restrain motion, thereby reducing the risk of potentially damaging stress upon a coupling module. In some embodiments, motion restriction elements 1422-1423 are typically successful in adequately restricting motion in one or two degrees of motion. These degrees of motion are typically along an axis in which the elements 1422-1423 possess most of their strength. For example, motion restriction elements 1422-1423 may constrain motion along a yaw and pitch axis but provide little or no constraint along the roll axis.

0074<figref idref="f0015">FIG. 14A</figref> illustrates an embodiment in which the motion restriction elements1422-1423 include one or more physical members that physically interact to restrain motion. <figref idref="f0016">FIG. 14B</figref> illustrates an embodiment in which the motion restriction elements 1422-1423 include one or more wire loops that oppose each other to restrain motion. <figref idref="f0016">FIG. 14C</figref> illustrates an embodiment in which the motion restriction elements 1422-1423 include a fabric that physically restrains motion. In alternate embodiments, motion restriction elements may be used to constrain motion along one or all axes.

0075<figref idref="f0017">FIGS. 15A-15B</figref> are schematic diagrams illustrating an exemplary interaction of components of an IMD that are part of an overmold 1522, which includes one or more soft or elastomeric components 1532 and one or more hard or non-elastomeric components 1531, which interface with a control module 1510. Non-elastomeric component 1531 may be shaped to mate with the module 1510 to provide motion restriction for the module. Non-elastomeric component 1531 may be mechanically connected to other modules using a motion restriction element(not shown). The overmold 1522 covers all of these components in this embodiment. A through hole 1551 may be located through the through the non-elastomeric component 1531 and elastomeric component 1532 to provide an attachment point for the device 1501. In some embodiments, IMD 1501 may be anchored in place using bone screws or other anchoring devices. Through holes 1551 permit IMD 1501 to be mechanically anchored to the patient once the device 1501 is positioned at a desired location. In the embodiment shown in <figref idref="f0017">FIG. 15A</figref>, a bone screw inserted into through hole 1551 would seat against non-elastomeric component 1531, but also encompassed are embodiments in which a bone screw would seat against another component, such as control module 1510..

0076<figref idref="f0017">FIG. 15B</figref> illustrates a top view of the device 1501 having elastomeric component 1532 of overmold 822 covering the non-elastomeric components 1531 that frame control module 1510. The through hole 1551 used as an attachment point is shown as part of non-elastomeric component 1531 that is covered by elastomeric component 1532. The shape of non-elastomeric component 1531 and control module 1510 are shown as being rectangular in this embodiment. However, one skilled in the art will recognize that any shape for non-elastomeric component 1531 and control module 1510 may be used.

0077In addition, overmold 1522 is shown in <figref idref="f0017">FIGS. 15A and 15B</figref> as substantially or completely encapsulating module 1510. However, overmold 1522 may also merely surround the module 1510 but not cover the top of the module that is surrounded by the hard component 1531. Such an arrangement may result in a smaller profile of the overall IMD.

0078A coupling module (not shown) passes around and through many of the elements of the overmold. This coupling module may be, but need not be, constrained within overmold 1522. In general, the coupling module may be expected to flex during implantation and use. In some embodiments of the invention, the coupling module may be routed in a channel (not shown) within the overmold.

0079<figref idref="f0018">FIGS. 16A-16B</figref> are a schematic diagrams illustrating a multi-module IMD 1601 having a triangular module arrangement. <figref idref="f0018">FIG. 16A</figref> illustrates an exploded view of IMD 1601. <figref idref="f0018">FIG. 16B</figref> illustrates a perspective view of IMD 1601. In this embodiment, another triangular arrangement of modules is shown with an overmold 1622 covering or at least partially encapsulating the modules. In this embodiment, overmold 1622 comprises a distinct slope interface 1641 that surrounds the periphery of IMD 1601. In this embodiment, slope interface 1641 is shown as a separate physical structure, such as a flexible band or ring. A coupling module 1651 is shown connecting two modules 1610-1611 without being restrained by the overmold 1622.