NEURAL STIMULATION SYSTEM PROVIDING AUTO ADJUSTMENT OF STIMULUS OUTPUT AS A FUNCTION OF SENSED IMPEDANCE

• US 20110190847A1
• Filed: 03/22/2011
• Published: 08/04/2011
• Est. Priority Date: 02/12/2002
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: King, John D.H., Thacker, James R.
• Granted Patent: US 8,626,312 B2
• Time in Patent Office: Days
• US Class Current: 607/46
• CPC Class Codes: A61N 1/36071 Pain
• CPC Class Codes: A61N 1/36139 with automatic adjustment
• CPC Class Codes: A61N 1/3615 Intensity

Abstract

A neural stimulation system automatically corrects or adjusts the stimulus magnitude (stimulation energy) in order to maintain a comfortable and effective stimulation therapy. Because the changes in impedance associated with the electrode-tissue interface can indicate obstruction of current flow and positional lead displacement, lead impedance can indicate the quantity of electrical stimulation energy that should be delivered to the target neural tissue to provide corrective adjustment. Hence, a change in impedance or morphology of an impedance curve may be used in a feedback loop to indicate that the stimulation energy needs to be adjusted and the system can effectively auto correct the magnitude of stimulation energy to maintain a desired therapeutic effect.

Claims

1-24. -24. (canceled)

25. A method for controlling a neurostimulation system, comprising:

applying stimulus current to neural tissue of a patient via at least one electrode of the neurostimulation system, the electrical signal being delivered in accordance with a stimulus parameter having a first value;

detecting a change in an impedance indicative of a coupling efficiency between the applied stimulus current and the neural tissue; and

based at least in part on the detected impedance change, automatically adjusting the value of the stimulus parameter from the first value to a second value different from the first value, without human intervention.

26. The method of claim 25, wherein automatically adjusting the value of the stimulus parameter includes changing at least one of an amplitude, pulse width, and frequency of the stimulus current.

27. The method of claim 25, wherein the neural tissue is spinal cord tissue.

28. The method of claim 25, wherein detecting a change in the impedance includes detecting an increase in impedance.

29. The method of claim 28, wherein automatically adjusting the value of the stimulus parameter includes increasing the amplitude of the stimulus current.

30. The method of claim 28, wherein detecting the increase in the impedance included detecting an increase correlated with an increase in the amplitude of the electrical stimulus.

31. The method of claim 25, wherein detecting a change in the impedance includes detecting a decrease in impedance.

32. The method of claim 31, wherein automatically adjusting the value of the stimulus parameter includes decreasing the amplitude of the stimulus current.

33. The method of claim 25, wherein detecting a change in the impedance includes detecting a change in impedance resulting from a build up of scar tissue on the at least one electrode.

34. The method of claim 25, wherein detecting a change in the impedance includes detecting a change in impedance resulting from a change in position of the at least one electrode relative to the patient.

35. The method of claim 25, wherein detecting a change in the impedance includes detecting a change in impedance resulting from a change in the patient'"'"'s posture.

36. The method of claim 25, wherein detecting a change in the impedance includes detecting a change in impedance as a function of time, and wherein the method further comprises establishing a trend for future changes in impedance.

37. The method of claim 25, wherein detecting a change in the impedance includes detecting a change in impedance by monitoring the applied electrical stimulus.

38. The method of claim 25, wherein detecting a change in the impedance includes applying an electrical signal in addition to the electrical stimulus and detecting a change in impedance by monitoring the additional electrical signal.

39. A neurostimulation system, comprising:

at least one electrode configured for being positioned in electrical communication with neural tissue of a patient when implanted;

an implantable pulse generator configured for applying a stimulus current to the neural tissue via the at least one electrode;

an impedance detector configured for detecting a change in an impedance indicative of a coupling efficiency between the applied stimulus current and the neural tissue; and

a processor configured for receiving an indication of an impedance change from the impedance detector; and

based at least in part on the detected impedance change and without human intervention, automatically adjusting a value of a stimulus parameter in accordance with which the implantable pulse generator delivers the applied stimulus current to the neural tissue via the at least one electrode.

40. The neurostimulation system of claim 39, wherein processor is configured for automatically adjusting the value of the stimulus parameter by changing at least one of an amplitude, pulse width, and frequency of the stimulus current.

41. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting an increase in impedance, and the processor is configured for automatically adjusting the value of the stimulus parameter by increasing the amplitude of the stimulus current in response to the detected increase in the impedance.

42. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting an increase in impedance, and the processor is configured for correlating the increase in the impedance with an increase in the amplitude of the electrical stimulus.

43. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting a decrease in impedance, and the processor is configured for automatically adjusting the value of the stimulus parameter by decreasing the amplitude of the stimulus current in response to the detected decrease in the impedance.

44. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting a decrease in impedance, and the processor is configured for correlating the decrease in the impedance with a decrease in the amplitude of the electrical stimulus.

45. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting a change in impedance as a function of time, and wherein the processor is further configured for establishing a trend for future changes in impedance.

46. The neurostimulation system of claim 39, wherein the impedance detector is configured for detecting a change in the impedance by detecting a change in impedance by monitoring the applied electrical stimulus.

47. The neurostimulation system of claim 39 wherein the impedance detector is configured for detecting a change in the impedance by applying an electrical signal in addition to the electrical stimulus and detecting a change in impedance by monitoring the additional electrical signal.