Patent Description:
Medical device that provide electrical stimulation and/or physiological sensing require an implantation site within the body of the patient that can accommodate the size and shape of the device while minimizing the intrusiveness experienced by the patient. Typically, a pocket is created within an area of soft tissues of the patient that is nearest the stimulation site while also being a convenient location for purposes of implantation and long-term use, such as below the clavicle for upper body stimulation sites. However, the nearest implantation site within an area of soft tissues may be distant from the stimulation therapy site where the stimulation and/or sensing occurs within the body.

To address this distance and to provide a smaller object at the therapy site, a medical lead is implanted to carry the stimulation and/or sensing signals between the medical device and the therapy site. A distal end of the lead that has electrodes is routed to the therapy site within the body while a proximal end is routed to the medical device to establish electrical connectivity to the medical device. Electrical conductors within the lead body carry the signals. Document <CIT> discloses an example of an implantable medical device.

In some cases, the distance of the route that the lead will follow between the implantation site of the medical device and the therapy site exceeds the length of the medical lead, and in that case a lead extension is also implanted. The lead extension has a proximal end that connects to the medical device to establish electrical connectivity, and the proximal end of the lead is connected to a distal end of the lead extension to further establish electrical connectivity. While the lead extension eliminates the issue of distance in some cases, the lead extension adds to the complexity of the medical system and implantation procedure.

The present invention provides an implantable medical device according to claim <NUM>.

Embodiments address issues such as these and others by providing a medical device that includes two housings. A first device housing includes the electrical circuitry for providing stimulation and/or sensing functions. A second device housing includes a compartment where the first device housing may be inserted, and the second device housing provides a lead bore where the proximal end of the lead may be inserted. The second device housing may be adapted for one or more locations within the body of the patent that might be unsuitable for the first device housing, such as locations that are more convenient and/or closer to the therapy site than would otherwise be possible.

Embodiments provide an implantable medical device that includes a first device housing and electrical circuitry within the first device housing. The electrical circuitry comprises electrical terminals that are present outside of the first device housing. The implantable medical device further includes a second device housing that has a lead bore and a device housing compartment. The first device housing is present within the device housing compartment, and electrical connectors are present within the lead bore. Electrical conductors electrically connect the electrical terminals to the electrical connectors.

Embodiments provide an implantable medical system that includes an implantable medical device and an implantable medical lead. The implantable medical device includes a first device housing and electrical circuitry within the first device housing. The electrical circuitry includes electrical terminals that are present outside of the first device housing. The implantable medical device includes a second device housing that has a lead bore and a device housing compartment. The first device housing is present within the device housing compartment, and electrical connectors are present within the lead bore. Electrical conductors electrically connect the electrical terminals to the electrical connectors. The implantable medical lead has a proximal and distal end, and the proximal end is present within the lead bore.

Embodiments that are not part of the invention provide a method of providing stimulation therapy that involves implanting an implantable medical device and implanting an implantable medical lead. The implantable medical device being implanted includes a first device housing and electrical circuitry within the first device housing. The electrical circuitry includes electrical terminals that are present outside of the first device housing. The implantable medical device being implanted further includes a second device housing comprising a lead bore and a device housing compartment, and the first device housing is present within the device housing compartment. Electrical connectors are present within the lead bore, and electrical conductors electrically connect the electrical terminals to the electrical connectors. The implantable medical lead being implanted includes a proximal and a distal end, and the distal end is positioned at a stimulation site while the proximal end is being inserted into the lead bore.

Embodiments include medical devices that have two housings where a first device housing includes the circuitry for providing stimulation and/or sensing and the second device housing includes a compartment for the first device housing. The second device housing also includes a lead bore that receives a proximal end of a medical lead, and the lead bore includes electrical connectors for establishing electrical connectivity with the proximal end of the lead. Electrical conductors are present within the second device housing and electrically interconnect electrical terminals of the first device housing with the electrical connectors within the lead bore.

<FIG> shows an example of a medical system <NUM> that has been implanted into a patient <NUM>. In this example, the patient is receiving deep brain stimulation therapy which provides electrical stimulation and/or sensing at a therapy site within the brain. It will be appreciated that embodiments of the medical system <NUM> may be used for other purposes and in other locations within the body of the patient <NUM>. For instance, the medical system may be used for other forms of neurological stimulation and/or sensing such as spinal cord sensing and/or stimulation, peripheral nerve sensing and/or stimulation, as well as cardiac sensing and/or stimulation, and the like.

The medical system <NUM> includes a medical device <NUM> and a medical lead <NUM> that is coupled to the medical device <NUM>. In this example, the medical device <NUM> is implanted directly onto the skull of the patient <NUM>. An area <NUM> may be prepared on the skull to create a depression for the positioning of the medical device <NUM> subcutaneously in the area <NUM>. This allows the medical device <NUM> to be positioned much closer to the hole within the skull where the lead <NUM> is inserted compared to a typical implantation site near the clavicle so that no lead extension is needed in this example.

As shown in <FIG>, the medical lead <NUM> extends from the medical device <NUM> to the insertion hole within the skull. The medical lead <NUM> extends through the brain to where distal end <NUM> of the lead <NUM> having electrodes <NUM> reaches the therapy site. The medical device <NUM> being located on the skull may then exchange stimulation and/or sensing signals with the electrodes <NUM> that have established an electrical interface to the brain tissue. It will be appreciated that the implantation site of the medical device <NUM> as shown in <FIG> is only an example, and that the medical device <NUM> may be implanted in various other locations on the skull or on other parts of the body of the patient <NUM>.

While this example of <FIG> shows a percutaneous lead <NUM> implanted within the brain of the patient <NUM>, it will be appreciated that the medical system <NUM> that includes the medical device <NUM> may be implanted in many other areas of the body of the patient <NUM> while utilizing aspects of the embodiments disclosed herein. It will also be appreciated that other variations in the medical system <NUM> may exist, such as utilizing other types of leads including paddle-style leads and the like.

<FIG> and <FIG> provide a more detailed view of the medical device <NUM>. Here, it can be seen that the medical device <NUM> includes a first device housing <NUM> that is positioned within a compartment <NUM> that is formed by a second device housing <NUM>. As discussed in further detail below, the first device housing <NUM> encloses electrical circuitry such as a stimulation engine, sensing circuits, a controller, a battery, and the like. Thus, the first device housing <NUM> may be assembled as a complete unit and then subsequently inserted into the compartment <NUM> of the second device housing <NUM> where the medical device <NUM> may then be completed. A medical adhesive or similar biocompatible material can be applied to fill in any voids that are present between the first device housing <NUM> and the second device housing <NUM>. The first device housing <NUM> of this example includes a main housing portion <NUM> as well as a top cap <NUM>, shown in <FIG> and <FIG>, which are discussed in more detail below. While the first device housing <NUM> is shown as having a rectangular shape with the top cap <NUM>, it will be appreciated that other shapes and configurations are also possible to allow the first device housing <NUM> to be inserted into an appropriately shaped and sized compartment <NUM> of the second device housing <NUM>.

Including both the first device housing <NUM> and the second device housing <NUM> for the medical device <NUM> offers several benefits. The first device housing <NUM> may be constructed of a shape and size so as to accommodate the desired circuitry, battery and the like regardless of the outer shape of the second device housing <NUM>. The first device housing <NUM> may also be constructed of a different material than the second device housing <NUM>, such as by utilizing a biocompatible metal or other electrically conductive material that offers better shielding from electromagnetic interference. This allows the first device housing to have a more universal application.

The second device housing <NUM> may be created with a shape and material that are more specific to the particular location being implanted. For example, the second device housing <NUM> may be constructed with a round disc-like shape as shown to better fit within a round depression created in the skull. Furthermore, the second device housing <NUM> may be constructed of a material such as a biocompatible polymer that offers protection for the first device housing <NUM> while also providing a suitable interface to the bone and subcutaneous tissues at the particular area of implantation.

The second device housing <NUM> also provides a lead bore <NUM> where electrical connectors are located, and the lead bore <NUM> includes an exterior opening <NUM>. As shown in <FIG>, a proximal end <NUM> of the medical lead <NUM> is being inserted through the opening <NUM> and into the lead bore <NUM>. The proximal end <NUM> of the lead <NUM> includes several proximal contacts <NUM> attached to a lead body <NUM> that establish electrical connections within the connectors within the lead bore <NUM>. The proximal contacts <NUM> are electrically connected by internal conductors of the lead <NUM> with the distal electrodes <NUM> shown in <FIG>. Once the proximal end <NUM> is fully inserted, the lead <NUM> may be secured in place by a set screw <NUM> that tightens against the proximal end <NUM>, such as against one of the proximal contacts <NUM>.

While the example shown has the round disc-like shape, it will be appreciated that the second device housing <NUM> may have many other shapes in other examples while providing both a lead bore <NUM> and a compartment <NUM> for the first device housing <NUM>. Furthermore, the orientation of the compartment <NUM> and lead bore <NUM> may vary from the parallel configuration shown, such as where the longitudinal dimension of each forms an angle with respect to each other, including a perpendicular orientation. Thus, the round disc-like shape is shown only for purposes of demonstrating one example. Furthermore, while the second device housing of this example may be constructed of a polymer such as polysulfone, or polyether ether ketone (PEEK) and the like, it will be appreciated that other biocompatible materials may instead be used such as a biocompatible metal. However, with a conductive material such as metal, the channels and bays should be coated with a non-conductive material such as polysulfone to electrically isolate the second housing from the conductors and connectors.

While the first housing <NUM> is located in the compartment <NUM>, it can be seen in the example shown that a portion of the end of the first housing <NUM> is not covered by the second housing <NUM>. Furthermore, this exposed portion of the first housing <NUM> may remain uncovered by medical adhesive, so that if the first housing <NUM> is constructed of a conductive material such as a metal, the first housing <NUM> may act as a node of the stimulation and sensing circuits, such as for unipolar stimulation. Additionally, for embodiments where the second housing <NUM> is constructed of a conductive material such as a metal, the second housing <NUM> may establish electrical contact with a conductive portion of the first housing <NUM> so that the second housing <NUM> also forms the electrical node of the stimulation and sensing circuits.

<FIG> shows the underside of this example of a complete medical device <NUM> while <FIG> shows the underside in perspective without the first device housing <NUM> being inserted. <FIG> shows the underside of the second device housing <NUM> alone. For this medical device <NUM>, the second device housing <NUM> may be molded or otherwise constructed with features that allow for the inclusion of the first device housing <NUM> within the compartment <NUM> and for the electrical connectivity that is necessary between the first device housing <NUM> and electrical connectors <NUM> within the lead bore <NUM> of the second device housing <NUM>.

As shown in <FIG>, a first bay <NUM> and a second bay <NUM> that are open to the exterior are formed in the underside of the second device housing. The second device housing <NUM> provides channels <NUM> that extend from the first bay <NUM> to the second bay <NUM>. The depth of the bays <NUM>, <NUM> and channels <NUM> in this example can be seen in the perspective view of <FIG>. Also shown in <FIG>, an aperture <NUM> is present in the wall of the first bay <NUM> to provide a location for a set screw block and corresponding set screw <NUM> of <FIG> within the lead bore <NUM>. In this example, the second device housing <NUM> also forms a notch <NUM> in the otherwise round periphery of the second device housing <NUM> where the opening <NUM> to the lead bore <NUM> is located. This notch <NUM> allows the lead <NUM> to begin an arc as it extends away from the opening <NUM> so as to then wrap around the second device housing <NUM> one or more times before extending to the hole in the skull in order to provide strain relief.

As shown in <FIG> and <FIG>, various items are present within the first bay <NUM>, and hence within the lead bore <NUM> that is further defined by the first bay <NUM>, including the set screw block <NUM> and electrical connectors <NUM> separated by non-conductive seals <NUM>. <FIG> shows a top end of the first device housing <NUM> is positioned within the second bay <NUM> upon the first device housing <NUM> being inserted into the compartment <NUM> as shown in <FIG>. A wall <NUM> is shown in the bay <NUM> in <FIG> which provides a hard stop for the insertion of the first device housing, as the top cap <NUM> abuts the wall <NUM> once the first device housing <NUM> is fully inserted.

Electrical terminals <NUM> in the form of feedthrough pins extend from the top cap <NUM> of the first device housing <NUM> to corresponding channels <NUM> once the top cap <NUM> reaches the wall <NUM>. Electrical conductors <NUM> are present within the channels <NUM> where one end of the conductors <NUM> makes electrical connection to a corresponding electrical connector <NUM> while another end of the conductors <NUM> makes electrical connection to a corresponding electrical terminal <NUM>. As can be seen in <FIG>, in this example, the conductors <NUM> include a portion <NUM> that drops to a lower position within the bay <NUM> so that the pad <NUM> resides immediately beneath the terminals <NUM> once the first device housing <NUM> is inserted. To facilitate creating contact, such as a weld or other electrically conductive bond between the conductor <NUM> and the terminal <NUM>, the end of the conductor <NUM> may form a conductive pad <NUM> with increased surface area. Alternatively, other forms of contact may occur between the conductor <NUM> and terminal <NUM>, such as a frictional engagement via a spring loaded connector of the conductor <NUM> in place of the conductive pad <NUM> that frictionally contacts the terminal <NUM>.

The top end of the first device housing <NUM> in relation to stimulation and/or sensing circuitry <NUM> is shown in more detail in <FIG>. As can be seen, the main portion <NUM> of the first device housing encloses the circuitry <NUM> while the top cap <NUM> provides for the electrical terminals <NUM> to be exposed outside of the first device housing <NUM> for purposes of electrical connection to the conductors <NUM>. The top cap <NUM> may establish a feedthrough that is a hermetic seal to further protect the circuitry <NUM> from bodily fluids that surround the medical device <NUM>. Additionally, the top cap <NUM> may provide a filtered feedthrough to reduce the amount of electrical noise that may be present on the conductors <NUM> that reaches the circuitry <NUM>.

Once the electrical connections have been established among the various components, a medical adhesive or other similar filler material <NUM> (represented as dots in <FIG> merely for purposes of illustration) may be applied to the underside of the second device housing <NUM>. The filler material <NUM> fills both the first bay <NUM> and the second bay <NUM> to encapsulate the components installed within those bays <NUM>, <NUM>. Additionally, the filter material <NUM> is applied within the channels <NUM> to encapsulate the conductors <NUM>. The filler material <NUM> may be applied to completely fill the bays <NUM>, <NUM> and channel <NUM> and create a flush underside surface for the second device housing <NUM>. The filler <NUM> thereby electrically isolates the components within the bays <NUM>, <NUM> and channels <NUM>.

Rather than installing all of the components and electrical connections prior to applying the filler material <NUM>, other approaches may be used. For instance, the components may be installed in the bay <NUM> and the channels <NUM> and then the bay <NUM> and channels <NUM> are filled while the bay <NUM> remains unfilled. Subsequently, the first device housing <NUM> is inserted into the compartment <NUM> with bonds being created between the terminals <NUM> and the pads <NUM>, and then the second may <NUM> is filled. As another possibility, the order may be reversed where the first device housing <NUM> is inserted with terminals being bonded to the pads <NUM> and the bay <NUM> filled while the bay <NUM> remains unfilled. Subsequently, the components of the first bay <NUM> are installed with connectors <NUM> being bonded to the conductors <NUM>, and the bay <NUM> is then filled.

Another feature that may be present for some embodiments is also shown in <FIG>, <FIG>, and <FIG>. A bridging channel <NUM> may be provided in the second device housing <NUM> for purposes of containing a bridging conductor that bridges multiple electrical connectors <NUM> in parallel to the same conductor <NUM> and hence to the same terminal <NUM> of the first device housing <NUM>. This may be used where the first device housing <NUM> has fewer electrical terminals <NUM> than the lead <NUM> has proximal contacts <NUM> and distal electrodes <NUM>. This allows all proximal contacts <NUM> and distal electrodes <NUM> to be active electrical nodes of the circuitry <NUM> when desired. The filler material <NUM> is also applied to the bridging channels <NUM> to encapsulate the bridging conductors.

<FIG> shows an example of the manufacturing operations that may be performed to create the medical device <NUM>. Initially, at an operation <NUM>, the connectors <NUM> and seals <NUM> as well as the set screw block <NUM> may be installed in the first bay <NUM>. Additionally, the conductors <NUM> routed through the channels <NUM> and are bonded to the corresponding connectors <NUM> such as by a weld. As discussed above, in one example, filler material may be added at this point except for the second bay <NUM>. However, in this example of <FIG>, all filler material is added at a later point.

At an operation <NUM>, the first device housing is inserted into the compartment <NUM> of the second device housing <NUM>. As discussed above in relation to <FIG> of this example, the second bay <NUM> includes the wall <NUM> that acts as a stop for the insertion of the first device housing <NUM> into the compartment <NUM>, and upon the top cap <NUM> reaching the wall <NUM>, the terminals <NUM> are aligned with the pads <NUM>. At an operation <NUM>, the terminals <NUM> are placed in contact with the conductors, such as by being bonded to the pads <NUM> via welds or other conductive bonds or by other forms of contact such as a frictional engagement. Once all the electrical connections are established, the bays <NUM>, <NUM> and channels <NUM> that have not previously been filled may be filled with the medical adhesive or other biocompatible filler material at an operation <NUM>. The medical device <NUM> is then ready for implantation.

Claim 1:
An implantable medical device, comprising:
a first device housing (<NUM>);
electrical circuitry within the first device housing (<NUM>), wherein the electrical circuitry comprises electrical terminals (<NUM>) that are present outside of the first device housing (<NUM>);
a second device housing (<NUM>) comprising a lead bore (<NUM>) and a device housing compartment (<NUM>), the first device housing (<NUM>) being present within the device housing compartment (<NUM>);
electrical connectors (<NUM>) within the lead bore (<NUM>); and
electrical conductors (<NUM>) electrically connecting the electrical terminals (<NUM>) to the electrical connectors (<NUM>).