Patent Description:
The present invention relates to an implantable neurostimulator according to claim <NUM>.

Implantable stimulation devices generate and deliver electrical stimuli to bodily nerves and tissues for the therapy of various biological disorders, such as:.

Typical implantable stimulation devices include a neurostimulator, one or more leads electrically coupled to the neurostimulator, and an array of stimulator electrodes on each lead. The stimulator electrodes are in contact with or near the bodily tissue to be stimulated. A pulse generator in the neurostimulator generates electrical pulses that are delivered by the electrodes to bodily tissue. The neurostimulator typically includes an implantable rounded case having circuitry such as a printed circuit board, a telemetry coil for communicating with an external programmer to control the electrical pulses, and a charging coil for charging the neurostimulator.

The neurostimulator also includes a header having one or more connector assemblies for receiving the leads, wherein the connector assemblies have one or more connector contacts for coupling to the leads. In common models of such neurostimulators, there are two connector assemblies in the header, each having eight contacts. However, to allow for greater range in stimulation parameters, it is desirable for the header to include more electrode contacts for coupling to the lead, for example, thirty-two contacts. At the same time, it is preferred to keep the case and header as small as possible and to maintain a curved configuration for patient comfort. Therefore, a proper neurostimulator design to accommodate thirty-two electrodes, without affecting device performance, is desirable.

It is also common for neurostimulators to house a telemetry coil in the header. However, this requires a feedthrough to couple the telemetry coil to resonant circuit components and transceiver circuitry in the case. This can add to the complexity of the device and lead to problems with hermeticity. Additionally, the feedthroughs require significant extra steps during manufacture, thus allowing for greater error and quality concerns.

Another disadvantage of having the telemetry coil in the header is that the coil and the feedthroughs connected to the coil take up space in the header, which may be limited based on the complexity of the stimulation system. At the same time, it is desirable to make stimulation devices smaller for patient comfort. Moreover, while previous neurostimulators had eight or sixteen contacts for coupling to the electrode leads, newer designs may include thirty-two or more contacts, further limiting space in the header.

Thus, there remains a need for improved stimulation devices and methods that optimize performance with an increased number of electrodes and selective positioning of the telemetry coil, while also having a small, rounded configuration for patient comfort that does not compromise device performance.

An implantable neurostimulator according to the preamble of claim <NUM> is disclosed in prior art documents <CIT> and <CIT>.

In accordance with one aspect of the present disclosure, not forming part of the invention, a tissue stimulation system is provided. The stimulation system has at least one implantable neurostimulation lead and an implantable neurostimulator. The neurostimulator includes at least one connector assembly configured for respectively receiving the at least one neurostimulation lead, a case, a circuit board positioned in the case, a telemetry coil positioned in the case that is electrically coupled to the circuit board and spaced a distance away from the circuit board, and a charging coil positioned in the case that is electrically coupled to the circuit board. In one embodiment, the telemetry coil is positioned on a spacer that spaces the telemetry coil the distance away from the circuit board. In a further embodiment, a plurality of pins are affixed to the spacer, wherein at least one of the pins electrically couples the telemetry coil to the circuit board, and at least one of the pins mechanically couples the telemetry coil to the circuit board.

In a second aspect of the present disclosure, not forming part of the invention, an implantable neurostimulator is provided. The neurostimulator has a case, a circuit board positioned in the case, a telemetry coil positioned in the case that is electrically coupled to the circuit board and spaced a distance away from the circuit board, and a charging coil positioned in the case that is electrically coupled to the circuit board. In one embodiment, the telemetry coil is positioned on a spacer that spaces the telemetry coil the distance away from the circuit board. In a further embodiment, a plurality of pins are affixed to the spacer, wherein at least one of the pins electrically couples the telemetry coil to the circuit board, and at least one of the pins mechanically couples the telemetry coil to the circuit board.

In a third aspect of the present disclosure, not forming part of the invention, a tissue stimulation system is provided that includes at least one implantable neurostimulation lead and an implantable neurostimulator. The neurostimulator has a header with at least one connector assembly configured for respectively receiving the at least one neurostimulation lead, a circuit board having programming circuitry, and a flex circuit coupled between the at least one connector assembly and the circuit board. In one embodiment, the system includes a feedthrough assembly with a plurality of pins coupled to the flex circuit that electrically couple the flex circuit to the at least one connector assembly. In another embodiment, one or more of the plurality of pins traverse through one or more holes in the flex circuit. In another embodiment, the feedthrough assembly has a metal flange forming a well containing an insulative material, and the pins extend from the flex circuit through the insulative material. In yet another embodiment, the at least one connector assembly has a plurality of connector contacts for electrically coupling with the neurostimulation lead, and the pins are electrically coupled to the connector contacts.

In a fourth aspect of the present disclosure, not forming part of the invention, an implantable neurostimulator is provided. The neurostimulator has at least one connector assembly configured for receiving at least one neurostimulation lead, a circuit board having programming circuitry, and a flex circuit coupled between the at least one connector assembly and the circuit board. In one embodiment, the system includes a feedthrough assembly with a plurality of pins coupled to the flex circuit that electrically couple the flex circuit to the at least one connector assembly. In another embodiment, one or more of the plurality of pins traverse through one or more holes in the flex circuit. In another embodiment, the feedthrough assembly has a metal flange forming a well containing an insulative material, and the pins extend from the flex circuit through the insulative material. In yet another embodiment, the at least one connector assembly has a plurality of connector contacts for electrically coupling with the neurostimulation lead, and the pins are electrically coupled to the connector contacts.

In a fifth aspect of the present disclosure, not forming part of the invention, a tissue stimulation system is provided that includes at least one implantable neurostimulation lead and an implantable neurostimulator. The neurostimulator has at least one connector assembly configured for respectively receiving the at least one neurostimulation lead, a fastener configured for securing the respective one of the at least one neurostimulation leads in the at least one connector assembly, and at least one septum, each having an outer block and an inner block framed within the outer block. Adjacent edges of the inner and outer blocks form at least one slot for receiving a tool for manipulating the fastener for securing the respective one of the at least one neurostimulation leads in the respective one of the at least one connector assembly. In one embodiment, the neurostimulator has a retainer in which the at least one connector assembly is positioned. In another embodiment, a connector block is coupled to each at least one connector assembly and has the fastener positioned therein. In another embodiment, the outer and inner blocks of the at least one septum are composed of silicone.

In yet another embodiment, the neurostimulator has a shell housing the at least one connector assembly, and the shell has a first transverse line and a second transverse line both aligned parallel to the at least one connector assembly. The first transverse line extends between first opposing ends of the shell, the second transverse line extends between second opposing ends of the shell, and the first transverse line is shorter than the second transverse line. In a further embodiment, at least one upper connector assembly longitudinally aligned along the first transverse line, and at least one lower connector assembly longitudinally aligned along the second transverse line. In yet a further embodiment, the neurostimulator has at least one upper strain relief member longitudinally aligned along the first transverse line and extending between an end of the at least one upper connector assembly and one of the first opposing ends of the shell, and at least one lower strain relief member longitudinally aligned along the second transverse line and extending between an end of the at least one lower connector assembly and one of the second opposing ends of the shell. The at least one upper strain relief member has a shorter length than the at least one lower strain relief member.

In a sixth aspect of the present disclosure, not forming part of the invention, an implantable neurostimulator is provided. The neurostimulator has at least one connector assembly configured for receiving a neurostimulation lead, a fastener configured for securing the respective one of the at least one neurostimulation leads in the at least one connector assembly, and at least one septum, each having an outer block and an inner block framed within the outer block. Adjacent edges of the inner and outer blocks form at least one slot for receiving a tool for manipulating the fastener for securing the respective one of the at least one neurostimulation leads in the respective one of the at least one connector assembly. In one embodiment, the neurostimulator has a retainer in which the at least one connector assembly is positioned. In another embodiment, a connector block is coupled to each at least one connector assembly and has the fastener positioned therein. In another embodiment, the outer and inner blocks of the at least one septum are composed of silicone.

In a seventh aspect of the present disclosure, not forming part of the invention, an implantable neurostimulator is provided. The neurostimulator has a connector header configured for receiving a neurostimulation lead, a divot formed in each of the opposing sides of the connector header, and a suture hole extending between the divots. In one embodiment, each divot has a plurality of side surfaces, and each side surface is angled less than <NUM> degrees from an outer surface of the connector header. In another embodiment, each divot has a bottom surface, and a terminating end of the suture hole is positioned at the bottom surface.

In an eighth aspect of the invention according to claim <NUM>, an implantable neurostimulator is provided. The neurostimulator has a shell having a first transverse line extending between first opposing ends of the shell, and a second transverse line extending between second opposing ends of the shell, wherein the first transverse line is shorter than the second transverse line. The neurostimulator also has at least one upper connector assembly and at least one lower connector assembly housed in the shell, each configured for receiving a neurostimulator lead, wherein the at least one upper connector assembly is longitudinally aligned along the first transverse line, and the at least one lower connector assembly is longitudinally aligned along the second transverse line. The neurostimulator also has at least one upper strain relief member longitudinally aligned along the first transverse line and extending between an end of the at least one upper connector assembly and one of the first opposing ends of the shell, and at least one lower strain relief member longitudinally aligned along the second transverse line and extending between an end of the at least one lower connector assembly and one of the second opposing ends of the shell. The at least one upper strain relief member has a shorter length than the at least one lower strain relief member.

In one embodiment, the at least one upper connector assembly and at least one lower connector assembly has contacts for electrically coupling to the respective electrode lead received therein. In another embodiment, the at least one upper connector assembly and at least one lower connector assembly are positioned in a retainer. In yet another embodiment, the neurostimulator has at least one upper connector block adjacent the at least one upper connector assembly and at least one lower connector block adjacent the at least one lower connector assembly. In yet another embodiment, each of the at least one upper connector block and at least one lower connector block has a fastener disposed therein for securing the respective electrode received in the at least one upper connector assembly and the at least one lower connector assembly.

Other and further aspects and features of the invention will be evident from reading the following detailed description of the preferred embodiments, which are intended to illustrate, not limit, the invention.

The drawings illustrate the design and utility of preferred embodiments of the present invention, in which similar elements are referred to by common reference numerals. In order to better appreciate how the above-recited and other advantages and objects of the present inventions are obtained, a more particular description of the present inventions briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:.

The description that follows relates to a spinal cord stimulation (SCS) system. However, it is to be understood that the while the invention lends itself well to applications in SCS, the invention, in its broadest aspects, may not be so limited. Rather, the invention may be used with any type of implantable electrical circuitry used to stimulate tissue. For example, the present invention may be used as part of a pacemaker, a defibrillator, a cochlear stimulator, a retinal stimulator, a stimulator configured to produce coordinated limb movement, a cortical stimulator, a deep brain stimulator, peripheral nerve stimulator, microstimulator, or in any other neural stimulator configured to treat urinary incontinence, sleep apnea, shoulder sublaxation, headache, etc..

Turning first to <FIG>, an exemplary SCS system <NUM> generally includes one or more (in this case, two) implantable neurostimulation leads <NUM>, a neurostimulator (i.e., an implantable pulse generator) (IPG) <NUM>, an external remote controller RC <NUM>, a clinician's programmer (CP) <NUM>, an External Trial Stimulator (ETS) <NUM>, and an external charger <NUM>.

The IPG <NUM> is physically connected via one or more percutaneous lead extensions <NUM> to the neurostimulation leads <NUM>, which carry a plurality of electrodes <NUM> arranged in an array. In the illustrated embodiment, the neurostimulation leads <NUM> are percutaneous leads, and to this end, the electrodes <NUM> are arranged in-line along the neurostimulation leads <NUM>. In alternative embodiments, the electrodes <NUM> may be arranged in a two-dimensional pattern on a single paddle lead. As will be described in further detail below, the IPG <NUM> includes pulse generation circuitry that delivers electrical stimulation energy in the form of a pulsed electrical waveform (i.e., a temporal series of electrical pulses) to the electrode array <NUM> in accordance with a set of stimulation parameters.

The ETS <NUM> may also be physically connected via the percutaneous lead extensions <NUM> and external cable <NUM> to the neurostimulation leads <NUM>. The ETS <NUM>, which has similar pulse generation circuitry as that of the IPG <NUM>, also delivers electrical stimulation energy in the form of a pulsed electrical waveform to the electrode array <NUM> in accordance with a set of stimulation parameters. The major difference between the ETS <NUM> and the IPG <NUM> is that the ETS <NUM> is a non-implantable device that is used on a trial basis after the neurostimulation leads <NUM> have been implanted and prior to implantation of the IPG <NUM>, to test the responsiveness of the stimulation that is to be provided.

The RC <NUM> may be used to telemetrically control the ETS <NUM> via a bidirectional inductive link <NUM>. Once the IPG <NUM> and neurostimulation leads <NUM> are implanted, the RC <NUM> may also be used to telemetrically control the IPG <NUM> via a bidirectional magnetic coupling link <NUM>. Such control allows the IPG <NUM> to be turned on or off and to be programmed with different stimulation parameter sets. The IPG <NUM> may also be operated to modify the programmed stimulation parameters to actively control the characteristics of the electrical stimulation energy output by the IPG <NUM>. It should be noted that rather than an IPG, the system <NUM> may alternatively utilize an implantable receiver-stimulator (not shown) connected to the lead <NUM>. In this case, the power source, e.g., a battery, for powering the implanted receiver, as well as control circuitry to command the receiver-stimulator, will be contained in an external controller/charger inductively coupled to the receiver-stimulator via an electromagnetic link.

The CP <NUM> provides clinician detailed stimulation parameters for programming the IPG <NUM> and ETS <NUM> in the operating room and in follow-up sessions. The CP <NUM> may perform this function by indirectly communicating with the IPG <NUM> or ETS <NUM>, through the RC <NUM>, via an IR communications link <NUM>. Alternatively, the CP <NUM> may directly communicate with the IPG <NUM> or ETS <NUM> via an RF communications link or magnetic coupling link (not shown). The clinician detailed stimulation parameters provided by the CP <NUM> are also used to program the RC <NUM>, so that the stimulation parameters can be subsequently modified by operation of the RC <NUM> in a stand-alone mode (i.e., without the assistance of the CP <NUM>).

The external charger <NUM> is a portable device used to transcutaneously charge the IPG <NUM> via an inductive link <NUM>. Once the IPG <NUM> has been programmed, and its power source has been charged by the external charger <NUM> or otherwise replenished, the IPG <NUM> may function as programmed without the RC <NUM> or CP <NUM> being present.

For purposes of brevity, the details of the RC <NUM>, CP <NUM>, ETS <NUM>, and external charger <NUM> will not be described herein. Details of exemplary embodiments of these devices are disclosed in <CIT>, which is expressly incorporated herein by reference.

As shown in <FIG>, the electrode leads <NUM> are implanted within the spinal column <NUM> of a patient <NUM>. The preferred placement of the neurostimulation leads <NUM> is adjacent, i.e., resting near, or upon the dura, adjacent to the spinal cord area to be stimulated. Due to the lack of space near the location where the electrode leads <NUM> exit the spinal column <NUM>, the IPG <NUM> is generally implanted in a surgically-made pocket either in the abdomen or above the buttocks. The IPG <NUM> may, of course, also be implanted in other locations of the patient's body. The lead extension <NUM> facilitates locating the IPG <NUM> away from the exit point of the electrode leads <NUM>. As there shown, the CP <NUM> communicates with the IPG <NUM> via the RC <NUM>.

Referring now to <FIG>, the external features of the neurostimulation leads <NUM> and the IPG <NUM> will be briefly described. In the illustrated embodiment, there are four stimulation leads <NUM>(<NUM>)-<NUM>(<NUM>), wherein neurostimulation lead <NUM>(<NUM>) has eight electrodes <NUM> (labeled E1-E8), neurostimulation lead <NUM>(<NUM>) has eight electrodes <NUM> (labeled E9-E16), neurostimulation lead <NUM>(<NUM>) has eight electrodes <NUM> (labeled E17-E24), and neurostimulation lead <NUM>(<NUM>) has eight electrodes <NUM> (labeled E24-E32). The actual number and shape of leads and electrodes will, of course, vary according to the intended application.

As shown in <FIG> and <FIG>, the IPG <NUM> comprises an outer case <NUM> for housing the electronic and other components (described in further detail below), and a header portion <NUM> coupled to the case <NUM> for receiving the proximal ends of the neurostimulation leads <NUM>(<NUM>)-<NUM>(<NUM>) for mating in a manner that electrically couples the electrodes <NUM> to the electronics within the case <NUM>.

The outer case <NUM> is composed of an electrically conductive, biocompatible material, such as titanium <NUM>-<NUM>, and forms a hermetically sealed compartment wherein the internal electronics are protected from the body tissue and fluids. In the illustrated embodiment, the case <NUM> has a rounded configuration with a maximum circular diameter D of about <NUM>, and preferably about <NUM>, and a maximum thickness W of about <NUM>, and preferably about <NUM>. The case <NUM> is formed using any suitable process, such as casting, molding, and the like. The header <NUM> has a rounded configuration that corresponds with that of the case <NUM>, such that the case <NUM> and the header <NUM> together form a rounded body.

As will be described in further detail below, the IPG <NUM> includes pulse generation circuitry <NUM> (see <FIG>) that provides electrical stimulation energy in the form of a pulsed electrical waveform to the electrode array <NUM> in accordance with a set of stimulation parameters programmed into the IPG <NUM>. Such stimulation parameters may comprise electrode combinations, which define the electrodes that are activated as anodes (positive), cathodes (negative), and turned off (zero), percentage of stimulation energy assigned to each electrode (fractionalized electrode configurations), and electrical pulse parameters, which define the pulse amplitude (measured in milliamps or volts depending on whether the IPG <NUM> supplies constant current or constant voltage to the electrode array <NUM>), pulse width (measured in microseconds), pulse rate (measured in pulses per second), and burst rate (measured as the stimulation on duration X and stimulation off duration Y).

Electrical stimulation will occur between two (or more) activated electrodes, one of which may be the IPG case <NUM>. Stimulation energy may be transmitted to the tissue in a monopolar or multipolar (e.g., bipolar, tripolar, etc.) fashion. Monopolar stimulation occurs when a selected one of the lead electrodes <NUM> is activated along with the case <NUM> of the IPG <NUM>, so that stimulation energy is transmitted between the selected electrode <NUM> and case <NUM>. Bipolar stimulation occurs when two of the lead electrodes <NUM> are activated as anode and cathode, so that stimulation energy is transmitted between the selected electrodes <NUM>. For example, an electrode on one lead <NUM> may be activated as an anode at the same time that an electrode on the same lead or another lead <NUM> is activated as a cathode. Tripolar stimulation occurs when three of the lead electrodes <NUM> are activated, two as anodes and the remaining one as a cathode, or two as cathodes and the remaining one as an anode. For example, two electrodes on one lead <NUM> may be activated as anodes at the same time that an electrode on another lead <NUM> is activated as a cathode.

The stimulation energy may be delivered between electrodes as monophasic electrical energy or multiphasic electrical energy. Monophasic electrical energy includes a series of pulses that are either all positive (anodic) or all negative (cathodic). Multiphasic electrical energy includes a series of pulses that alternate between positive and negative. For example, multiphasic electrical energy may include a series of biphasic pulses, with each biphasic pulse including a cathodic (negative) stimulation pulse and an anodic (positive) recharge pulse that is generated after the stimulation pulse to prevent direct current charge transfer through the tissue, thereby avoiding electrode degradation and cell trauma. That is, charge is conveyed through the electrode-tissue interface via current at an electrode during a stimulation period (the length of the stimulation pulse), and then pulled back off the electrode-tissue interface via an oppositely polarized current at the same electrode during a recharge period (the length of the recharge pulse).

Referring to <FIG> which show opposing internal sides of case <NUM>, in performing the above-described stimulation energy generation function, the IPG <NUM> comprises multiple electronic components, including an electronic substrate assembly <NUM> and a battery <NUM> contained within the case <NUM>, and a flex circuit <NUM> (see <FIG>) coupled to the electronic substrate assembly <NUM>. The flex circuit <NUM> serves to couple the electronic substrate assembly <NUM> to the electronic components in the header <NUM>, which will be discussed in further detail below. The electronic substrate assembly <NUM> includes a printed circuit board (PCB) <NUM> to which the previously described pulse generation circuitry <NUM> is mounted in the form of microprocessors, integrated circuits, capacitors, and other electronic components. The electronic substrate assembly <NUM> further comprises a telemetry coil <NUM>, a charging coil <NUM>, and telemetry/charging circuitry <NUM> mounted to the PCB <NUM>. While a portion of the electronic components of the IPG <NUM> will be described in further detail below, additional details of the IPG <NUM> and electrical components are disclosed in <CIT>, which was previously incorporated herein.

The telemetry coil <NUM> and charging coil <NUM> are positioned on opposing sides of the PCB <NUM>. Significantly, as shown in <FIG>, the electronic substrate assembly <NUM> further comprises a spacer <NUM> on which the telemetry coil <NUM> is positioned to space the telemetry coil <NUM> a distance Dt away from the PCB <NUM>. In the illustrated embodiment, the spacer <NUM> is a bobbin <NUM>. The bobbin <NUM> has a main body <NUM> and an outer flange <NUM> extending around the periphery of the main body <NUM> on which the telemetry coil <NUM> sits, such that the coil <NUM> is wound around the main body <NUM> in a shape corresponding to that of the main body <NUM>. Here, the telemetry coil <NUM> and the main body <NUM> of the bobbin <NUM> have a D-shaped configuration for encompassing a wide area in the case <NUM> to improve coupling, and hence the reliability of data transfer, between the telemetry coil <NUM> and the RC <NUM>. In addition to maintaining the telemetry coil <NUM> a distance away from the PCB <NUM>, the bobbin <NUM> is beneficial for manufacture, as the bobbin <NUM> provides a base on which to shape the telemetry coil <NUM>, creating a more consistent design than freeform winding of the telemetry coil <NUM>.

A number of pins <NUM>, <NUM> are affixed to the bobbin for coupling the telemetry coil <NUM> to the PCB <NUM>. In the illustrated embodiment, the bobbin <NUM> has three holes <NUM> extending through the main body <NUM> of the bobbin <NUM> for receiving three pins <NUM>, <NUM>. In this embodiment, two of the pins <NUM> electrically connect the telemetry coil <NUM> to the PCB <NUM>, and in particular, one pin <NUM> connects the ground port of the telemetry coil <NUM>, and the other pin connects the signal port of the telemetry coil <NUM>. The third pin <NUM> mechanically connects the telemetry coil <NUM> to the PCB <NUM>. In the illustrated embodiment, the two holes <NUM> for receiving the two electrical pins <NUM> are located on one side of the main body <NUM> of the bobbin <NUM>, and the one hole <NUM> for receiving the mechanical pin <NUM> is located on an opposing side of the main body <NUM> of the bobbin <NUM>. The pins <NUM>, <NUM> may be secured in the holes <NUM> by welding or other suitable means. In this manner, the pins <NUM>, <NUM> facilitate secure, accurate placement of the telemetry coil <NUM> relative to the PCB <NUM>, while the two pins <NUM> also provide an electrical connection between the telemetry coil <NUM> and the PCB <NUM>. In other embodiments, only one pin may be used to electrically connect the telemetry coil <NUM> to the PCB <NUM>, or more pins may be used to electrically and/or mechanically connect the telemetry coil <NUM> to the PCB <NUM>.

Notably, many typical IPGs contain a charging coil in the case and a telemetry coil in the header. In the illustrated embodiment, however, positioning both the charging coil <NUM> and the telemetry coil <NUM> in the case <NUM> allows more room in the header <NUM> for other electronic components. Additionally, positioning the telemetry coil <NUM> in the case <NUM> eliminates the need for a feedthrough that connects the electronic substrate assembly <NUM> with the telemetry coil <NUM>, as opposed to when a telemetry coil is in the header.

To realize potential effects associated with positioning both the telemetry coil <NUM> and charging coil <NUM> in the case, it is helpful to note the operation of the coils <NUM>, <NUM>. Regarding the telemetry coil <NUM>, wireless data telemetry between the RC <NUM> and the IPG <NUM> occurs via inductive coupling, for example, magnetic inductive coupling. This coupling occurs between the telemetry coil <NUM> in the IPG <NUM> and a corresponding external coil (not shown) in the RC <NUM>. When data is sent from the RC <NUM> to the IPG <NUM>, the external coil in the RC <NUM> is energized with an alternating current (AC). This energizing of the external coil to transfer data can occur using a Frequency Shift Keying (FSK) protocol, for example, in which digital data bits in a stream are represented by different frequencies, as disclosed in <CIT>, which is incorporated herein by reference. Energizing the external coil with these frequencies produces a magnetic field, which in turn induces a voltage in the telemetry coil <NUM> in the IPG <NUM>, producing a corresponding current signal when provided a closed loop path. This voltage and/or current signal can then be demodulated to recover the original data. Transmitting data in the reverse, from the telemetry coil <NUM> to the external coil, occurs in essentially the same manner.

Regarding the charging coil <NUM>, when power is to be transmitted from the external charger <NUM> to the IPG <NUM>, the charging coil <NUM> is energized with an alternating current (AC). Such energizing is generally of a constant frequency and may be of a larger magnitude than that used during data transfer with the telemetry coil <NUM>, but the basic operation is similar. The IPG <NUM> can also communicate back to the external charger <NUM> by modulating the impedance of the charging coil <NUM>. This change in impedance is reflected back to the external charger <NUM>, which demodulates the reflection to recover the transmitted data. This means of transmitting data from the IPG <NUM> to the external charger <NUM> is known as Load Shift Keying (LSK) and is useful to communicate data relevant during charging of the battery <NUM> in the IPG <NUM>, such as the capacity of the battery <NUM>, extent of charging completed, and other charging variables. LSK communication between an IPG and external charger is further detailed in <CIT>, which is incorporated herein by reference.

One possible issue that may arise with positioning both the telemetry coil <NUM> and the charging coil <NUM> in the case <NUM> is that the mutual inductance of the coils <NUM>, <NUM> may interfere with each other if both coils <NUM>, <NUM> are receiving and transmitting data at the same time. One method of addressing this is to include decoupling circuitry (not shown) for decoupling the charging coil <NUM> from the charging circuitry <NUM> during periods of telemetry between the IPG <NUM> and the RC <NUM>. The decoupling circuitry may be activated based on one or more operating factors, for example, when the telemetry coil <NUM> is sending or receiving data to/from the RC <NUM>, or when the charging circuitry <NUM> detects no charging alternating current for the charging coil <NUM> to receive.

In another method, the LSK data signal is used to transmit serial data to the external charger <NUM> during charging, as is typical, and is also used as a control signal to reduce loading of the telemetry coil <NUM> during data telemetry between the IPG <NUM> and the RC <NUM>. Using the preexisting LSK circuitry in this method requires no change in telemetry circuitry other than to program the IPG <NUM> circuitry to assert LSK data during periods of data telemetry. Thus, the enhanced circuitry improves reliability of telemetry between the RC <NUM> and the telemetry coil <NUM> without substantial circuitry changes. Additional information regarding the enhanced circuitry is detailed in Application No. <CIT>, which is incorporated herein by reference.

The bobbin <NUM> also provides operational benefits with positioning the telemetry coil <NUM> and the charging coil <NUM> in the case <NUM>. For example, the bobbin <NUM> lessens the interference between the coils <NUM>, <NUM> by increasing the distance between the telemetry coil <NUM> and the charging coil <NUM>, as described above. Additionally, the bobbin <NUM> places the telemetry coil <NUM> in closer proximity to the case <NUM> to optimize telemetry using resistance from the case <NUM>. To illustrate, the telemetry coil <NUM> may communicate on a seven-band frequency that is achieved by attaining a loss in transmission from resistance, e.g., resistance from adjacent material. In prior embodiments wherein the telemetry coil is positioned in the header, the header provides the resistance needed to obtain the ideal frequency. In the present embodiment, in positioning the telemetry coil <NUM> closer to the case <NUM>, the case <NUM> provides the resistance needed to create the desired seven-band frequency for telemetry coil <NUM> transmission.

As mentioned above, the flex circuit <NUM> serves to couple the electronic substrate assembly <NUM> to the electronic components in the header <NUM>. In particular, the flex circuit <NUM> is coupled to the PCB <NUM> and also to feedthrough pins, described in further detail below, that in turn are coupled to lead extensions <NUM> received in the header <NUM>. As the flex circuit <NUM> is a flexible metallic component (see e.g., <FIG>), the flex circuit <NUM> serves as an interface between the electronic substrate assembly <NUM> and the electronic components in the header <NUM> to provide an electrical coupling function along with the ability to be bent in a suitable configuration to accommodate the size and structure of the IPG <NUM>.

Coupling the flex circuit <NUM> to the PCB <NUM> eliminates the need for soldering an additional plate to the PCB <NUM>, making manufacture more efficient and eliminating related quality issues that may otherwise arise. In some embodiments, the flex circuit <NUM> may be permanently coupled to the PCB <NUM>, for example, by soldering, laser-welding, applying conductive epoxy or similar adhesive, or crimping. In other embodiments, the flex circuit <NUM> may be detachably coupled to the PCB <NUM>, for example, by edge connectors such as zero insertion force connectors, snap-fit mechanisms, friction-fit mechanisms, and fasteners such as screws. In one embodiment, the substrate of the flex circuit <NUM> is composed primarily of polyamide, which may be the same material from which the PCB <NUM> is primarily composed. Other materials may also be used for the substrate of the flex circuit <NUM>.

As mentioned above, the electronic components within the case <NUM> are electrically coupled to the electrodes <NUM> via lead extensions <NUM> received in the header <NUM>, as shown in <FIG>. Referring to <FIG> and <FIG>, the header <NUM> includes: a shell <NUM> coupled to the case <NUM>; a plurality of ports <NUM>; a retainer <NUM>; one or more connector assemblies <NUM> positioned in the retainer <NUM>; a corresponding number of connector blocks <NUM> positioned in the retainer <NUM>; one or more septums <NUM>; and a plurality of strain relief members <NUM>.

The shell <NUM> is formed using any suitable process, such as casting, molding, and the like, and is composed of a rigid material that does not interfere with the electrical functions of the IPG <NUM>, such as thermoset. The plurality of ports <NUM> extend through the shell <NUM> and are configured for receiving the lead extensions <NUM>. Preferably, the number of ports <NUM> corresponds to the number of lead extensions <NUM>. For example, in the illustrated embodiment, there are four lead extensions <NUM> and four ports <NUM>. The header ports <NUM> are also aligned with retainer ports <NUM>, such that the lead extensions <NUM> are received in the header ports <NUM> and then in the retainer <NUM> through the retainer ports <NUM>. The retainer ports <NUM> (in this illustrated embodiment, four ports) are in turn aligned with the connector assemblies <NUM>, such that the lead extensions <NUM> are received through the retainer ports <NUM> and then within the connector assemblies <NUM>.

As shown in <FIG>, the retainer <NUM> receives the connector assemblies <NUM> in corresponding retainer channels <NUM> that hold each respective connector assembly <NUM> in position. The retainer <NUM> is preferably composed of a rigid material, e.g., thermoplastic, such that the connector assemblies <NUM> can be affixed relative to each other. In one embodiment, the connector assemblies <NUM> are releasably disposed in the retainer <NUM> in a suitable manner, such as with an interference fit, snap connection, binders, or other suitable mechanisms. Partitions <NUM> in the retainer <NUM> keep the connector assemblies <NUM> separated to minimize interference.

The connector assemblies <NUM> receive and make electrical contact with the lead extensions <NUM>. Each connector assembly <NUM> has a housing <NUM>, a hollow center region <NUM> extending between a proximal end <NUM> and a distal end <NUM> of the housing <NUM>, a plurality of openings <NUM> transversely formed through the wall of the housing <NUM>, and a plurality of connector contacts <NUM> located within the hollow center region <NUM>. In the illustrated embodiment, there are four connector assemblies <NUM> aligned in a 2x2 configuration to make efficient use of space. Specifically, there are two upper assemblies <NUM> and two lower assemblies <NUM>, wherein the two lower assemblies <NUM> are designated as being closer to the case <NUM> than the two upper assemblies <NUM>. Other embodiments may include one assembly <NUM>, or two assemblies <NUM> or more arranged in a manner suited to the configuration of the IPG <NUM>. Suitable materials for the housing <NUM> include, for example, silicone and polyurethane, and multiple materials may be included. Each lead extension <NUM> is received through the distal end <NUM> of the respective housing <NUM> into the respective hollow center region <NUM>.

The openings <NUM> in the housing <NUM> extend from an outer surface of the housing <NUM> to the hollow center region <NUM>. Preferably, the housing openings <NUM> are linearly aligned along a side surface of the housing <NUM>. Each opening <NUM> provides access to a corresponding connector contact <NUM> within the housing <NUM>. The connector contacts <NUM> are electrically coupled to the electronic substrate assembly <NUM> in the case <NUM> by a plurality of feedthrough pins, which are explained below in greater detail.

When the lead extensions <NUM> are received in the connector assemblies <NUM>, the connector contacts <NUM> electrically couple with terminals <NUM> disposed on the lead extensions <NUM>. The terminals <NUM> are in turn coupled to the lead electrodes <NUM> with conductive wires (not shown). Preferably, the number and spacing of the connector contacts <NUM> in each connector assembly <NUM> correspond to the number and spacing of the terminals <NUM> on each lead extension <NUM> to optimize coupling. In the illustrated embodiment, each of the four connector assemblies <NUM> has eight contacts <NUM>, and each of the four lead extensions <NUM> has eight terminals <NUM>. In this manner, when a lead extension <NUM> is received in the hollow center region <NUM> of the connector assembly <NUM>, each connector contact <NUM> electrically couples to a corresponding terminal <NUM> on the lead extension <NUM>. This results in coupling between the electronic substrate assembly <NUM>, which is coupled to the connector contacts <NUM> by the flex circuit <NUM> and the feedthrough pins, and the electrodes <NUM>, which are coupled to the terminals <NUM>.

The retainer <NUM> has a number of end stops <NUM> each located at the proximal ends <NUM> of the housings <NUM> of the connector assemblies <NUM>. The end stops <NUM> are typically formed of a compressible material, such as silicone, and may be shaped as a block or alternatively have a curved bowl-shaped configuration. The end stops <NUM> help to set the pitch for placement of the connector contacts <NUM> during manufacture, for example, during precision-based processes such as laser soldering, to prevent irregular placement of the connector assemblies <NUM> that would lead to increased expense and quality issues. Also, during operation of the IPG <NUM>, the end stops <NUM> help limit movement of the connector assemblies <NUM> to optimize transmission of electrical pulses from the connector assemblies <NUM> to the lead electrodes <NUM>. Additional details regarding setting of pitch and use of end stops for connector assemblies are further described in <CIT>, and <CIT>, which are incorporated herein by reference.

The connector blocks <NUM> are located at the distal end <NUM> of the housing <NUM> and may also be coupled to the housing <NUM> and/or a wall of the retainer <NUM>. In the illustrated embodiment featuring the 2x2 connector assembly configuration, there are two upper connector blocks <NUM> adjacent the two upper assemblies <NUM> and two lower connector blocks <NUM> adjacent the lower assemblies <NUM>. Each connector block <NUM> defines a port <NUM> aligned with the hollow center region <NUM> for receiving a lead extension <NUM>. Each connector block <NUM> also has an aperture <NUM> on a side of the connector block <NUM> through which a fastener <NUM>, such as a setscrew or pin, is inserted and secured against the lead extension <NUM> received therein. This helps to prevent undesirable detachment of the lead extensions <NUM> from the IPG <NUM> and to optimize electrical coupling between the lead terminals <NUM> and connector contacts <NUM>.

The septums <NUM> have one or more slots <NUM> aligned with the connector block apertures <NUM> for receiving a fastening tool to secure the fastener <NUM> in each aperture <NUM>. The septums <NUM> are positioned adjacent to, and may also be coupled to, the connector blocks <NUM>. In the illustrated embodiment, two septums <NUM> are positioned on opposing sides of the header <NUM>, wherein each septum <NUM> is adjacent to two connector blocks <NUM>. Each septum <NUM> has an outer block <NUM> and an inner block <NUM>, as shown in <FIG>, wherein the outer block <NUM> frames the inner block <NUM>, as shown in <FIG>. The blocks <NUM>, <NUM> are composed of a compressible material, such as silicone. The demarcation between the blocks <NUM>, <NUM> forms the slots <NUM> for receiving the fastening tool. For example, the upper edge of the inner block <NUM> forms an upper slot <NUM> with the outer block <NUM>, and the lower edge of the inner block <NUM> forms a lower slot <NUM> with the outer block <NUM>. Additionally, as shown in <FIG>, the upper slot <NUM> in each septum <NUM> is adjacent to the aperture <NUM> in each upper connector block <NUM>, and the lower slot <NUM> in each septum <NUM> is adjacent to the aperture <NUM> in the lower connector block <NUM>.

Notably, in other devices wherein a septum only includes one block, the block is typically pierced with a knife to create the slot for receiving the fastening tool. However, this often results in coring of the material, wherein the cored material hinders insertion of the fastener. Additionally, silicone can demonstrate a tendency to "self-heal," such that a slot formed by piercing a silicone block could close at least partially over time. However, by implementing two silicone blocks that are pushed together, as in the illustrated embodiment, the tendency to self-heal is mitigated, and the slot remains intact.

Each septum <NUM> is positioned in an opening <NUM> formed through a surface of the header <NUM> (see <FIG>), wherein edges of the opening <NUM> extend over the space underneath to form a frame <NUM>, and the septum <NUM> is positioned under the frame <NUM>. In typical manufacturing practices, the septum is pushed from outside the header into an opening in the header. However, this often results in the septum becoming loose and being expelled from the header. In the present embodiment, however, the septum <NUM> is pushed into the opening <NUM> from inside the header <NUM>, such that the frame <NUM> edges extending over the opening <NUM> prevent the septum <NUM> from moving outside the opening <NUM>. An adhesive, such as epoxy, is also applied to adhere the septum <NUM> to the header <NUM>, such that both mechanical and adhesive elements hold the septum <NUM> in place. Additional details regarding the connector assemblies and the components associated therewith are found in <CIT>, <CIT>, and <CIT>, which are incorporated herein by reference.

The strain relief members <NUM> in the header <NUM> extend between each of the retainer ports <NUM> and the header ports <NUM>. In the illustrated embodiment, there are four strain relief members <NUM> that correspond with the 2x2 configuration of the connector assemblies <NUM>, such that there are two upper and two lower strain relief members <NUM>. The strain relief members <NUM> are formed as annular seals that help to prevent current leakage outside the header <NUM> and to hold the lead extensions <NUM> in position when inserted in the connector assemblies <NUM> while preventing damage to the lead extensions <NUM>. To correspond with the curved formation of the header <NUM>, the lower strain relief members <NUM> have a longer length than the upper strain relief members <NUM>. This is because there is more space between the distal end <NUM> of the lower connector assembly <NUM> and retainer port <NUM> and the corresponding header port <NUM> than between the upper connector assembly <NUM> and retainer port <NUM> and the corresponding header port <NUM>.

In the illustrated embodiment, the header <NUM> also features a suture hole <NUM> that extends between opposing sides of the header <NUM>. To illustrate, a suture needle can go through suture hole <NUM> by entering one side of the header <NUM> and exiting on the other side. A clinician implanting the IPG <NUM> may thus use a suture needle with the suture hole <NUM> to affix the IPG <NUM> to bodily tissue to help hold the IPG <NUM> in place. Each side of the suture hole <NUM> is surrounded by a divot <NUM> in an outer surface of the header <NUM>. The divot <NUM> is cut into the outer surface of the header <NUM> and has a plurality of side surfaces <NUM>, each side surface <NUM> preferably angled less than <NUM> degrees from the outer surface of the header <NUM>, and a bottom surface <NUM> where the suture hole <NUM> is positioned. The divot <NUM> and its configuration allow for ease in accessing the header <NUM> with a suture needle, particularly a curved suture needle, to affix the IPG <NUM> to bodily tissue.

Referring to <FIG>, a feedthrough assembly <NUM> electrically couples the electronic substrate assembly <NUM> with the connector assemblies <NUM>. The feedthrough assembly <NUM> includes a plurality of feedthrough pins <NUM>, a metal flange <NUM> defining a well <NUM>, and one or more ceramic plates <NUM> positioned in the well <NUM>.

The feedthrough pins <NUM> are formed of <NUM> wire composed of <NUM>/<NUM> platinum/iridium. In other feedthrough assemblies, the pins are composed of <NUM>/<NUM> platinum/iridium, however, this is less ductile and less compatible with soldering processes during manufacture. Preferably, the number of feedthrough pins <NUM> corresponds to the number of connector contacts <NUM> in the connector assemblies <NUM>. In the illustrated embodiment, there are thirty-two feedthrough pins <NUM>. The feedthrough pins <NUM> are coupled to the PCB <NUM> and extend through the case <NUM> and header <NUM> to the connector assemblies <NUM>, where the pins <NUM> are coupled to the connector contacts <NUM>. The feedthrough pins <NUM> may be coupled to the connector contacts <NUM> by any suitable method including, for example, welding, soldering, and the like. Notably, the feedthrough pins <NUM> are sufficiently long to reach the connector contacts <NUM> without requiring an additional wire to be soldered to each pin <NUM>. This eliminates the need for additional manufacturing steps, thus limiting production costs and quality issues that would otherwise arise.

As mentioned above, the feedthrough pins <NUM> are each coupled to the flex circuit <NUM>, which may be achieved in various manners. In the illustrated embodiment, each of the feedthrough pins <NUM> is inserted in a corresponding hole <NUM> in the flex circuit <NUM> (see <FIG>). To insert the feedthrough pins <NUM> through the flex circuit <NUM> during manufacture, the flex circuit <NUM> is initially flat, wherein each of the feedthrough pins <NUM> is inserted through the corresponding hole <NUM>. Using laser soldering, gold braze is applied on the underside of each hole <NUM> around each pin <NUM> and seeps through the holes <NUM> to seal the pins <NUM> in the holes <NUM>. This provides a metallurgical adhesive and electrical connection, which may be advantageous over other sealants that only serve as an adhesive. Conductive epoxy may also be used to seal the pins <NUM> in the holes <NUM>. The flex circuit <NUM> is then bent into a curved configuration to suitably fit in the IPG <NUM> and to orient the pins <NUM> upward for insertion through the header <NUM>.

In another embodiment, the feedthrough pins <NUM> are attached to an edge of the flex circuit <NUM>, for example, by laser-soldering or with a conductive epoxy. In another embodiment, a portion of the pins <NUM> are attached to an edge of the flex circuit <NUM>, and the remaining pins are inserted through holes <NUM> in the flex circuit <NUM>.

In entering the header <NUM>, the feedthrough pins <NUM> extend through the metal flange <NUM>, which is located at the base of the header <NUM>. The metal flange <NUM> is composed of a biocompatible material, such as titanium. As mentioned above, the metal flange <NUM> defines the well <NUM>, which is occupied by the ceramic plates <NUM>. The ceramic plates <NUM> are fused to the metal flange <NUM> with gold braze. In the illustrated embodiment, two ceramic plates <NUM> are positioned adjacent each other in the well <NUM>. Alternative embodiments may consist of only one ceramic plate <NUM> that occupies the well <NUM>. The ceramic plates <NUM> have a number of holes <NUM> corresponding to the number of feedthrough pins <NUM>, such that each pin <NUM> extends through one corresponding hole <NUM>. The pins <NUM> are fused to the ceramic plates <NUM> with gold braze that is applied on the underside of the plates <NUM> and seeps through the holes <NUM> to cover the pins <NUM> along the length of the holes <NUM>.

The ceramic plates <NUM> have a lower coefficient of expansion than the titanium of the metal flange <NUM>, such that when the components are heated to extremely high temperatures during manufacture, the ceramic plates <NUM> expand less than the flange <NUM>. As a result, less of the gold braze can seep from between the metal flange <NUM> and the ceramic plates <NUM>. Also, since the holes <NUM> receiving the pins <NUM> in the plates <NUM> do not widen significantly, the gold braze securing the pins <NUM> is substantially prevented from seeping through the holes <NUM>, thus serving to stabilize the pins <NUM>.

Claim 1:
An implantable neurostimulator (<NUM>), comprising:
a shell (<NUM>) having a first transverse line extending between first opposing ends of the shell, and a second transverse line extending between second opposing ends of the shell, wherein the first transverse line is shorter than the second transverse line;
at least one upper connector assembly (<NUM>) and at least one lower connector assembly (<NUM>) housed in the shell (<NUM>), each configured for receiving a neurostimulation lead, wherein the at least one upper connector assembly is longitudinally aligned along the first transverse line, and the at least one lower connector assembly is longitudinally aligned along the second transverse line; and
at least one upper strain relief member (<NUM>) longitudinally aligned along the first transverse line and extending between an end of the at least one upper connector assembly (<NUM>) and one of the first opposing ends of the shell (<NUM>), and at least one lower strain relief member (<NUM>) longitudinally aligned along the second transverse line and extending between an end of the at least one lower connector assembly (<NUM>) and one of the second opposing ends of the shell (<NUM>), characterized in that the at least one upper strain relief member has a shorter length than the at least one lower strain relief member.