Rechargeable spinal cord stimulator system

• US 20030120323A1
• Filed: 11/27/2002
• Published: 06/26/2003
• Est. Priority Date: 07/27/1999
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: Mann Woods, Carla, Meadows, Paul M., Chen, Joey, Payne, David H., Peterson, David K.
• Granted Patent: US 6,895,280 B2
• Time in Patent Office: Days
• US Class Current: 607/46
• CPC Class Codes: A61N 1/0553 Paddle shaped electrodes, e.g. for laminotomy
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/36185 Selection of the electrode configuration
• CPC Class Codes: A61N 1/37241 providing test stimulations
• CPC Class Codes: A61N 1/37247 User interfaces, e.g. input or presentation means
• CPC Class Codes: A61N 1/37252 Details of algorithms or data aspects of communication system, e.g. handshaking, transmitting specific data or segmenting data
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H01H 85/201 for connecting a fuse in a lead and adapted to be supported by the lead alone
• CPC Class Codes: H01H 85/32 Indicating lamp structurally associated with the protective device

Abstract

A spinal cord stimulation (SCS) system includes multiple electrodes, multiple, independently programmable, stimulation channels within an implantable pulse generator (IPG) which channels can provide concurrent, but unique stimulation fields, permitting virtual electrodes to be realized. The SCS system includes a replenishable power source (e.g., rechargeable battery), that may be recharged using transcutaneous power transmissions between antenna coil pairs. An external charger unit, having its own rechargeable battery can be used to charge the IPG replenishable power source. A real-time clock can provide an auto-run schedule for daily stimulation. An included bi-directional telemetry link in the system informs the patient or clinician the status of the system, including the state of charge of the IPG battery. Other processing circuitry in the IPG allows electrode impedance measurements to be made. Further circuitry in the external battery charger can provide alignment detection for the coil pairs.

Claims

1. A spinal cord stimulation system comprising:

a multi-channel implantable pulse generator (IPG) having a replenishable power source, the IPG having a housing which contains IPG processing circuitry;

an implantable electrode array detachably connected to the IPG, the electrode array having a multiplicity of n electrodes (En) thereon; and

a multiplicity of m stimulation channels provided by the IPG, wherein each stimulation channel is independently programmable with different stimulation parameters,

wherein m is equal to or less than n, and m is 2 or greater.

2. The spinal cord stimulation system of claim 1, further comprising:

means for non-invasively charging the replenishable power source.

3. The spinal cord stimulation system of claim 1, wherein the different stimulation parameters include:

pulsewidth, stimulation amplitude, repetition rate or pulses per second (pps), and an electrode configuration that may be either monopolar or bipolar.

4. The spinal cord stimulation system of claim 3,

wherein the IPG comprises processing circuitry including:

a control logic circuit, a timer logic circuit, a microcontroller circuit, and a memory circuit coupled to the microcontroller circuit; and

wherein the control logic, timer logic and microcontroller circuits are responsive to programming signals stored in the memory circuit to generate stimulation pulses having a specified amplitude, pulsewidth and repetition rate (pps).

5. The spinal cord stimulation system of claim 1,

wherein the IPG includes an independent, bi-directional current source, connected to each of the n electrodes;

wherein each of the bi-directional current sources is electrically connected through a coupling capacitor to one of the n electrodes; and

wherein each of the bi-directional current sources may be separately controlled to actively direct a current pulse of a selected amplitude and polarity to its respectively-connected electrode.

6. The spinal cord stimulation system of claim 1, further comprising:

an indifferent electrode,

wherein the n electrodes and the indifferent electrode may be selectively grouped into at least m sets of electrodes, each set representing an independently controllable stimulation channel, each set having at least two electrodes,

thereby providing m stimulation channels that may be either monopolar or bipolar electrode configurations.

7. The spinal cord stimulation system of claim 6,

wherein a current pulse is generated for a first channel by actively directing a pulse of a respective amplitude and polarity for a time period equal to a selected pulse width to a first group of anodic electrodes within the first channel, while actively directing a current pulse of a respective amplitude and opposite polarity for the selected pulse width to a second group of cathodic electrodes within the first channel, the sum of all the anodic amplitude currents in the first channel being equal to the sum of all the cathodic amplitude currents, whereby charge balance is maintained in the first channel;

and

wherein a current pulse is generated for a second channel by actively directing a second current pulse of a respective amplitude and polarity for a time period equal to a selected second pulse width to a selected group of anodic electrodes within the second channel, while actively directing a second current pulse of a respective amplitude and opposite polarity for the selected second pulse width to a selected group of cathodic electrodes within the second channel, the sum of all the anodic amplitude currents in the second channel being equal to the sum of all the cathodic amplitude currents, whereby charge balance is maintained in the second channel; and

wherein a current pulse is similarly generated for each of the m channels, whereby charge balance is maintained in each of the m channels.

8. The spinal cord stimulation system of claim 6, wherein at least one of the m sets of electrodes includes the indifferent electrode, thereby providing a monopolar electrode configuration.

9. The spinal cord stimulation system of claim 6, further comprising:

an arbitration means for selectively preventing overlap of current pulses amongst the m channels.

10. The spinal cord stimulation system of claim 6, further comprising:

a low impedance switching matrix within the IPG, the switching matrix having a multiplicity of input ports selectively connected to a multiplicity of output nodes, each output node coupled to one of the n electrodes and the indifferent electrode, whereby connections to any subset of the n number of electrodes and the indifferent electrode is permitted.

11. The spinal cord stimulation system of claim 6, further comprising:

programmable output current digital to analog converters connected to each electrode node,

wherein any electrode node, when enabled, can be grouped with any other electrode node that is enabled at the same time to form the m sets of electrodes, each set representing a channel.

12. The spinal cord stimulation system of claim 1, further comprising:

external components including a handheld programmer that may be selectively placed in telecommunicative contact with the IPG;

a clinician programmer that is selectively coupled with the handheld programmer (HHP); and

a portable charger that may be inductively coupled with the IPG in order to recharge the IPG power source.

13. The spinal cord stimulation system of claim 1, further comprising:

an external trial stimulator (ETS); and

a percutaneous extension which temporarily couples the ETS with the implantable electrode array.

14. The spinal cord stimulation system of claim 1, wherein the replenishable power source in the IPG comprises a rechargeable battery.

15. The spinal cord stimulation system of claim 14, wherein the rechargeable battery is a lithium-ion battery having at least 720 mWhr capacity.

16. The spinal cord stimulation system of claim 14, further comprising:

means for non-invasively recharging the rechargeable battery through the skin.

17. The spinal cord stimulation system of claim 1, wherein the IPG contains independent, bi-directional output current sources connected to each of the n electrodes, thereby providing independently programmable, current-controlled, stimulation channels.

18. The spinal cord stimulation system of claim 1, further comprising:

an arbitration circuit means for permitting the multiplicity of m stimulation channels to operate concurrently without interference between stimulation channels.

19. The spinal cord stimulation system of claim 1, further comprising:

an indifferent electrode, and

wherein the IPG further comprises;

an impedance measuring circuit to measure the impedance between any two of the n electrodes and the indifferent electrode.

20. The spinal cord stimulation system of claim 19, wherein the impedance measuring circuit measures the voltage potential between any two of the n electrodes and the indifferent electrode, which voltage measure is used to compute electrode impedance.

21. The spinal cord stimulation system of claim 20, wherein the impedance measuring circuit includes a processor IC that converts analog voltage measured by the measurement circuit to a digital value, which digital value is thereafter used to compute electrode impedance.

22. The spinal cord stimulation system of claim 21, further comprising:

coupling capacitors connected to each of the multiplicity of n electrodes, wherein the impedance measuring circuit includes an analog IC that measures the voltage at prescribed conditions on the circuit side of the coupling capacitor.

23. The spinal cord stimulation system of claim 22,

wherein the analog IC includes a sample and hold circuit for sampling and holding the voltage appearing across a selected pair of electrodes while a specified current pulse having a known current amplitude and width is applied thereto;

and

wherein the IPG processing circuitry includes the impedance measuring circuit for computing the impedance of the selected pair of electrodes based on the sampled voltage and known current amplitude.

24. The spinal cord stimulation system of claim 23, wherein the sample and hold circuit includes means for sampling the voltage across the selected pair of electrodes at a time that is approximately in the middle of the width of the current pulse applied to the selected pair of electrodes.

25. The spinal cord stimulation system of claim 1, wherein the IPG contains a soft ramping circuit that ramps up the stimulation pulse magnitude at the beginning of a burst of stimulation pulses in at least one channel.

26. The spinal cord stimulation system of claim 1, wherein the IPG housing is made of titanium 6-4.

27. A spinal cord stimulation system comprising:

implantable components including a multi-channel implantable pulse generator (IPG) having a replenishable power source;

an electrode array detachably connected to the IPG, the electrode array having a multiplicity of n electrodes (En) thereon; and

a real-time clock contained in the IPG to permit an auto-run schedule for operation of the IPG at certain times of the day.

28. The spinal cord stimulation system of claim 27, further comprising m independently controllable channels,

wherein each stimulation channel is independently programmable with different stimulation parameters,

wherein m is equal to or less than n, and m is 2 or greater.

29. The spinal cord stimulation system of claim 28, further including arbitration means for selectively preventing overlap of current pulses amongst the m stimulation channels.

30. The spinal cord stimulation system of claim 27, further comprising:

an indifferent electrode,

wherein the n electrodes and the indifferent electrode may be selectively grouped into at least m sets of electrodes, each set representing an independently controllable stimulation channel, each set having at least two electrodes; and

,

thereby providing m stimulation channels that may be set to either monopolar or bipolar electrode configurations.

31. The spinal cord stimulation system of claim 27, further comprising:

an IPG housing which is made of titanium 6-4.

32. A spinal cord stimulation system comprising:

an implantable, multi-channel implantable pulse generator (IPG) having a replenishable power source;

an implantable electrode array detachably connected to the IPG, the electrode array having a multiplicity of n electrodes (En) thereon;

a secondary, implanted coil coupled electrically to the replenishable power source; and

an external battery charger including;

a primary coil;

a rechargeable battery contained in the charger, electrically coupled to the primary coil; and

a power amplifier for applying alternating current derived from the rechargeable battery in the charger to the primary coil,

whereby the alternating current in the primary coil is transcutaneously transferred to the secondary implanted coil to the replenishable power source contained in the IPG.

33. The spinal cord stimulation system of claim 32, wherein the battery charger is portable.

34. The spinal cord stimulation system of claim 32, further comprising:

a means for using household AC power to charge up the rechargeable battery in the battery charger.

35. The spinal cord stimulation system of claim 32, further comprising:

alignment circuitry for detecting alignment between the primary and secondary coils, the alignment circuitry including a back telemetry receiver for monitoring the magnitude of the ac voltage at the primary coil as applied by the power amplifier,

wherein reflected impedance associated with energy magnetically coupled through the primary coil is monitored.

36. The spinal cord stimulation system of claim 35, further comprising:

an alarm generator that generates an audible alarm signal in response to changes sensed in the reflected impedance monitored by the back telemetry receiver,

37. The spinal cord stimulation system of claim 36, wherein the alarm generator broadcasts a first audible tone when the primary coil is misaligned with the secondary coil, and the first audible tone stops the broadcast when the primary coil is properly aligned with the secondary coil.

38. The spinal cord stimulation system of claim 32, further comprising:

a charge complete and protection circuitry that detects when the replenishable power source is fully charged, and wherein said replenishable power source comprises a rechargeable battery, said charge complete and protection circuitry comprising;

monitoring circuitry that monitors the voltage of the rechargeable battery and the charging current flowing to the rechargeable battery; and

a rectifier circuit in the IPG,

wherein the monitoring circuitry generates a flag signal when the rechargeable battery voltage and charging current reach prescribed levels, which prescribed levels indicate the battery is fully charged;

wherein the rectifier circuit is switchable between a full-wave rectifier circuit and a half-wave rectifier circuit;

wherein the rectifier circuit is switched to operate as the full-wave rectifier circuit during charging of the battery, and wherein the flag signal causes the rectifier circuit to switch to a half-wave rectifier circuit when the battery is fully charged, whereby modulation of the rectifier circuit between a full-wave rectifier circuit and a half-wave rectifier circuit is used to indicate whether the battery is fully charged; and

wherein the charge complete detection circuitry detects the switching of the rectifier circuit from a full-wave rectifier circuit to a half-wave rectifier circuit by the change in reflected impedance sensed at the primary coil.

39. The spinal cord stimulation system of claim 32, further comprising:

an IPG housing made from titanium 6-4.

40. A method for implanting a spinal cord stimulator system into a patient for stimulation therapy, the method comprising:

(a) implanting a nerve stimulation lead with a distally located, multi-electrode array placed near target tissue, said lead having a lead connector on the proximal end;

(b) connecting the lead connector to a percutaneous extension;

(c) externalizing the percutaneous extension through the skin;

(d) connecting an external trial stimulator (ETS) to the externalized lead extension;

(e) programming the stimulation parameters at first optimal values;

(f) waiting a specified period of time and re-programming the stimulation parameters to second optimal values;

(g) disconnecting the percutanous extension from the lead connector;

(h) connecting a multi-channel, implantable pulse generator to the lead connector;

(i) implanting the implantable pulse generator, while programmed to the second, optimal stimulation parameters.

41. A method of charging a rechargeable battery contained within an implantable pulse generator (IPG), which IPG is connected to an implanted, secondary coil antenna, the method employing an external battery charger, which charger contains a rechargeable battery electrically connected to an external, primary antenna coil, the method comprising:

(a) charging the rechargeable battery in the external battery charger using an external power source;

(b) aligning the primary antenna coil with the implanted secondary coil;

(c) broadcasting electromagnetic energy through the primary antenna coil;

(d) receiving the broadcast electromagnetic energy through the secondary antenna coil, whereby an alternating current is produced in the secondary coil;

(e) rectifying the induced, alternating current received by the secondary coil;

(f) charging the rechargeable battery carried within the IPG, while monitoring the charging current or voltage across the battery as the battery is being charged to prevent overcharging; and

(g) stopping the charging at the battery charger when the current or voltage at the battery in the IPG reaches a prescribed level.

42. The method of claim 41, further comprising:

(h) sensing the change in rectification in the IPG using circuitry means located in the external battery charger, to thereby sense when the rechargeable battery in the IPG is fully charged.

43. The method of claim 42, wherein sensing the change in rectification in step (h) comprises:

switching from a full-wave to a half-wave rectifier circuit when the battery in the IPG is fully charged, which decreases or stops charging to the IPG battery;

sensing the reflected impedance change at the primary coil caused by a change from switching from the full-wave rectifier circuit to the half-wave rectifier circuit, the change indicating that the IPG battery is fully charged.

44. The method of claim 43, further comprising:

(i) providing an alarm signal employing circuitry located external to the IPG, upon sensing a change in rectification in step (h), thereby indicating the battery is fully charged.

45. A spinal cord stimulation system comprising:

an implantable pulse generator (IPG) having a housing made of titanium 6-4.

46. An implantable pulse generator (IPG) comprising:

a housing which is made of titanium 6-4.