Implantable head located radiofrequency coupled neurostimulation system for head pain
An implantable head-mounted, radiofrequency (RF) coupled, unibody peripheral neurostimulation system is provided for implantation in the head for the purpose of treating chronic head pain, including migraine. The system may include an implantable pulse generator (IPG) from which multiple stimulating leads may extend sufficient to allow for adequate stimulation over multiple regions of the head, preferably including the frontal, parietal and occipital regions. A lead may include an extended body, along which may be disposed a plurality of surface metal electrodes (SME), which may be subdivided into a plurality of electrode arrays. A plurality of internal metal wires may run a portion of its length and connect the IPG's internal circuit to the SME. The IPG may include an RF receiver coil and an application specific integrated circuit. The IPG may be capable of functional connection to an external RF unit for purposes that may include power, diagnostics, and programming.
1. A system for controlling power delivery from an external power transfer system (EPTS) to at least one implantable neurostimulation system (INS), said system comprising:
an EPTS disposed outside a body; and
at least one INS disposed beneath a dermis layer of the body;
the EPTS including:
a transmit coil, or a group of transmit coils disposed in series, each transmit coil corresponding to a respective INS;
a transmit coil driver circuit operable to drive the group of one or more transmit coils with a resonant current having a peak magnitude; and
a back telemetry circuit operable to receive a message communicated by an INS;
each of said at least one INS respectively including:
a receive coil tuned to the resonant frequency of the corresponding transmit coil and operable to receive power transferred therefrom when in proximity thereto;
a plurality of electrodes;
an electrode driver circuit for driving the plurality of electrodes;
a current regulator circuit having an input to which the received power is coupled, and operable to provide on an output thereof a regulated electrode current to the electrode driver circuit;
a monitoring circuit operable to determine whether the received power is sufficient to achieve current regulation of the current regulator circuit; and
a back telemetry circuit operable to communicate a message to the EPTS;
wherein:
each respective INS is operable to communicate a respective message requesting a change in power transfer from the EPTS based upon a determination from the respective currrent regulator circuit; and
the EPTS is operable to adjust the transmit coil driver circuit to change the peak magnitude of the resonant current, based on respective messages received from one or more respective INS.
2. The system of claim 1 , wherein:
each respective message includes a request to increase power transfer from the EPTS when the respective current regulator circuit is not achieving current regulation; and
the EPTS is further operable to adjust the transmit coil driver circuit to increase the peak magnitude of the resonant current, in response to receiving a respective message from any respective INS requesting an increase in power transfer.
3. The system of claim 2 , wherein:
the EPTS is further operable to adjust the transmit coil driver circuit to decrease the peak magnitude of the resonant current, when no respective message requesting an increase in power transfer from the EPTS has been received from any respective INS for at least a certain period of time.
4. The system of claim 1 , wherein:
each respective message includes a request to decrease power transfer from the EPTS when the respective current regulator circuit is achieving current regulation; and
the EPTS is further operable to adjust the transmit coil driver circuit to decrease the peak magnitude of the resonant current, in response to receiving a respective message from every respective INS requesting a decrease in power transfer.
5. The system of claim 1 , wherein the respective monitoring circuit within each respective INS is operable to:
compare the respective electrode current provided by the respective current regulator circuit against a respective prescribed electrode current for the respective electrode driver circuit corresponding to a stimulation configuration programmed therein; and
determine that the respective current regulator circuit is achieving current regulation when the respective electrode current is greater than or equal to the respective prescribed electrode current.
6. The system of claim 1 , wherein each respective INS further comprises:
a respective resonant rectifier circuit having an input coupled to the respective receive coil, and having an output coupled to the input of the respective current regulator circuit, said respective resonant rectifier circuit operable to generate on its respective output a rectified voltage.
7. The system of claim 6 , wherein each respective INS further comprises:
a respective de-tuning circuit coupled to the respective receive coil, being operable to de-tune the respective receive coil to substantially inhibit power transfer from the EPTS to the respective INS.
8. The system of claim 1 , wherein:
each respective INS further comprises a respective charge storage device; and
each respective current regulator circuit is further operable to provide on a second output thereof a charging current to the respective charge storage device.
9. The system of claim 8 , wherein:
each respective charge storage device comprises a supercapacitor.
10. The system of claim 1 , wherein each respective INS is head-located beneath the dermis layer of a patient.
11. A neurostimulation system, comprising:
a power unit for being disposed external to and proximate a dermis layer including:
a variable power generator,
a controller to control the output power level of the variable power generator,
a power unit power coupler for coupling power over the dermis layer, and
a power unit telemetry system for receiving information across the dermis layer for input to the controller; and
an implantable neurostimulator including:
at least one neurostimulator lead with at least one array of stimulation electrodes,
an electrode driver for driving the electrodes with a desired power and wherein the implantable neurostimulator requires a total power to operate,
a current regulator for driving the electrode driver with a regulated current,
a current regulation detector for detecting information regarding a regulation status of the current regulator,
a neurostimulator power coupler for coupling power over the dermis layer for input to the electrode driver and the current regulator,
a neurostimulator telemetry system for transmitting information across the dermis layer to the power source telemetry system, and
a processor for determining information regarding the regulation status of the current regulator from the regulation detector to allow a determination to be made as to if the current regulator has fallen out of regulation, which provides an indication that the coupled power from the neurostimulator power coupler is insufficient to deliver the total power required for the implantable neurostimulator to operate based on the output of the current regulation detector and transmitting the determined information regarding regulation status of the current regulator to the controller via the telemetry system in the power unit;
wherein the controller in the power unit increases or decreases the power delivered to the implantable neurostimulator as a function of determined power determined information regarding the regulation status of the current regulation by the processor.
12. The neurostimulation system of claim 11 , wherein power unit and neurostimulator power couplers each comprise at least one coil.
13. The neurostimulation system of claim 12 , wherein the variable power generator generates alternating current power.
14. The neurostimulation system of claim 13 , wherein the controller varies the power generated by varying a voltage of the variable power generator.
15. The neurostimulation system of claim 11 , wherein the implantable neurostimulator further comprises a charge storage device that is powered by the current regulator.
16. The neurostimulation system of claim 11 , wherein the power unit power coupler is inductively coupled to the neurostimulator power coupler.
17. The neurostimulation system of claim 11 , wherein the neurostimulator and the power unit telemetry systems each communicate information across the dermis layer through the respective power unit and neurostimulator power couplers.