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

• US 20070208394A1
• Filed: 05/10/2007
• Published: 09/06/2007
• Est. Priority Date: 02/12/2002
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: King, John, Thacker, James
• Granted Patent: US 7,742,823 B2
• Time in Patent Office: Days
• US Class Current: 607/62
• 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 of neural stimulation using a neurostimulator, the method comprising:

correlating impedance changes with predicted stimulation energy adjustments;

measuring a change in impedance indicative of variations in the coupling efficiency between stimulation energy output from the neurostimulator and neural tissue; and

automatically adjusting the stimulation energy output from the neurostimulator based on the predicted stimulation energy adjustments and the measured impedance change to compensate for the variations in the coupling efficiency by maintaining the stimulation energy delivered to the neural tissue at a set level.

26. The method of claim 25, wherein the stimulation energy output from the neurostimulator is automatically adjusted by varying pulse amplitude, pulsewidth, frequency of pulses or some combination of these three stimulus parameters.

27. The method of claim 25, further comprising cross-referencing the measured impedance change with the correlated impedance changes to determine the adjustment of the stimulation energy output from the neurostimulator.

28. The method of claim 25, further comprising:

initially storing the correlated measured impedance changes and predicted stimulation energy adjustments; and

subsequently analyzing the stored correlated measured impedance changes and predicted stimulation energy adjustments to determine the predicted stimulation energy adjustment correlated to the measured impedance change.

29. The method of claim 28, wherein the correlated measured impedance changes and predicted stimulation energy adjustments are stored in a look-up table.

30. The method of claim 25, wherein the impedance changes are correlated with the predicted stimulation energy adjustments by having a patient implanted with the neurostimulator make positional movements to induce changes in measured impedance and recording impedance measurements as a function of the positional movements.

31. The method of claim 30, wherein the positional movements comprise sitting to lying, standing to lying, sitting to standing, twisting the torso to one or the other side, standing to sitting, and running.

32. The method of claim 30, wherein the impedance changes are correlated with the predicted stimulation energy adjustments further by recording associated changes in sensation reported by the patient.

33. The method of claim 30, wherein the impedance changes are correlated with the predicted stimulation energy adjustments further by varying the stimulation energy output from the neurostimulator at each particular patient position and determining the perception threshold at the particular patient position and the maximum comfort level at the particular patient position.

34. The method of claim 25, wherein the correlated impedance changes are characteristic impedance waveform morphologies, the impedance change measurement comprises measuring a characteristic impedance waveform morphology, and the stimulation energy output from the neurostimulator is automatically adjusted based on the predicted stimulation energy adjustments and the measured characteristic impedance waveform morphology.

35. A method of neural stimulation, the method comprising:

outputting a constant electrical stimulation current from a neurostimulator at a first level;

measuring a change in impedance indicative of coupling efficiency between the electrical stimulation current output from the neurostimulator and neural tissue; and

automatically adjusting the constant electrical stimulation current subsequently output from the neurostimulator to a second level different from the first level.

36. The method of claim 35, further comprising cross-referencing the measured impedance change with the correlated impedance changes to determine the adjustment of the electrical stimulation current subsequently output from the neurostimulator.

37. The method of claim 35, further comprising:

initially storing the correlated measured impedance changes and predicted electrical stimulation current adjustments; and

subsequently analyzing the stored correlated measured impedance changes and predicted electrical stimulation current adjustments to determine the predicted electrical stimulation current adjustment correlated to the measured impedance change.

38. The method of claim 37, wherein the correlated measured impedance changes and predicted electrical stimulation current adjustments are stored in a look-up table.

39. The method of claim 35, wherein the impedance changes are correlated with the predicted electrical stimulation current adjustments by having a patient implanted with the neurostimulator make positional movements to induce changes in measured impedance change and recording impedance measurements as a function of the positional movements.

40. The method of claim 39, wherein the positional movements comprise sitting to lying, standing to lying, sitting to standing, twisting the torso to one or the other side, standing to sitting, and running.

41. The method of claim 39, wherein the impedance changes are correlated with the predicted electrical stimulation current adjustments by recording associated changes in sensation reported by the patient.

42. The method of claim 39, wherein the impedance changes are correlated with the predicted electrical stimulation current adjustments further by varying the electrical stimulation current output from the neurostimulator at each particular patient position and determining the perception threshold at the particular patient position and the maximum comfort level at the particular patient position.

43. The method of claim 35, wherein the correlated impedance changes are characteristic impedance waveform morphologies, the impedance change measurement comprises measuring a characteristic impedance waveform morphology, and the electrical stimulation current output from the neurostimulator is automatically adjusted based on the predicted electrical stimulation current adjustments and the measured characteristic impedance waveform morphology.

44. The method of claim 35, wherein the constant electrical stimulation current subsequently output from the neurostimulator is automatically adjusted to compensate for the variations in the coupling efficiency by maintaining the constant electrical stimulation current delivered to the neural tissue at a set level.

45. A method of neural stimulation using a neurostimulator, the method comprising:

correlating impedance changes with predicted stimulation energy adjustments;

measuring a change in impedance indicative of variations in the coupling efficiency between stimulation energy output from the neurostimulator and neural tissue;

cross-referencing the measured impedance change with the correlated impedance changes to determine the adjustment of the stimulation energy output from the neurostimulator; and

automatically adjusting the stimulation energy output from the neurostimulator in accordance with the determined adjustment of the stimulation energy output in order to compensate for the variations in the coupling efficiency.

46. The method of claim 45, wherein the stimulation energy output from the neurostimulator is automatically automatically by varying pulse amplitude, pulsewidth, frequency of pulses or some combination of these three stimulus parameters.

47. The method of claim 45, further comprising initially storing the correlated measured impedance changes and predicted stimulation energy adjustments.

48. The method of claim 47, wherein the correlated measured impedance changes and predicted stimulation energy adjustments are stored in a look-up table.

49. The method of claim 45, wherein the impedance changes are correlated with the predicted stimulation energy adjustments by having a patient implanted with the neurostimulator make positional movements to induce changes in measured impedance and recording impedance measurements as a function of the positional movements.

50. The method of claim 49, wherein the positional movements comprise sitting to lying, standing to lying, sitting to standing, twisting the torso to one or the other side, standing to sitting, and running.

51. The method of claim 49, wherein the impedance changes are correlated with the predicted stimulation energy adjustments further by recording associated changes in sensation reported by the patient.

52. The method of claim 49, wherein the impedance changes are correlated with the predicted stimulation energy adjustments further by varying the stimulation energy output from the neurostimulator at each particular patient position and determining the perception threshold at the particular patient position and the maximum comfort level at the particular patient position.

53. The method of claim 45, wherein the correlated impedance changes are characteristic impedance waveform morphologies, the impedance change measurement comprises measuring a characteristic impedance waveform morphology, and the measured impedance waveform morphology is cross-referenced with the correlated characteristic impedance waveform morphologies to determine the adjustment of the stimulation energy output from the neurostimulator.

54. The method of claim 45, wherein the stimulation energy output from the neurostimulator is automatically adjusted to compensate for the variations in the coupling efficiency by maintaining the stimulation energy delivered to the neural tissue at a set level.