Seizure prediction

• US 8,594,779 B2
• Filed: 04/30/2007
• Issued: 11/26/2013
• Est. Priority Date: 04/30/2007
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Denison, Timothy J., Santa, Wesley A.
• Primary Examiner(s): Mallari, Patricia
• Assistant Examiner(s): JANG, CHRISTIAN YONGKYUN
• Application Number:
  US11/799,031
• Publication Number:
  US 20080269630A1
• Time in Patent Office: 2,402 Days
• Field of Search: 600/544, 600/545, 600/547, 607/45
• US Class Current: 600/544
• CPC Class Codes: A61B 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/389 Electromyography [EMG]
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61B 5/4839 combined with drug delivery
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: A61N 1/36025 for treating a mental or cerebral condition
• CPC Class Codes: A61N 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

Seizure prediction systems and methods include measuring impedance and a potential within a brain of a patient to determine whether the brain is in a state indicative of a possibility of seizure. In some embodiments, at least one of the measured impedance or the measured potential may be used as a primary indication of the brain state indicative of a possibility of seizure. In one embodiment, if one of the measured impedance or the measured potential indicates a seizure, the other measurement (impedance or potential) may be used to validate whether the brain is in the state indicative of the possibility of seizure.

Claims

1. A method comprising:

receiving, with a processor, impedance measurements indicative of an impedance of a brain of a patient, wherein the impedance of the brain is indicative of a physiological state of the brain;

receiving, with the processor, potential measurements indicative of a potential of the brain;

selecting, with the processor, a frequency component of a waveform of the impedance measurements from a plurality of frequency components of the waveform of the impedance measurements; and

determining, with the processor, whether the brain is in a state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements.

2. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain to generate the potential measurements by at least measuring the potential via at least one of electroencephalography (EEG) or electroencephalography (ECoG).

3. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain to generate the potential measurements by at least measuring the potential of the brain at a different time than measuring the impedance of the brain to generate the impedance measurements.

4. The method of claim 1, further comprising measuring, with a sensing module, the impedance of the brain of the patient to generate the impedance measurements and measuring the potential of the brain to generate the potential measurements by at least alternating between measuring the impedance of the brain and measuring the potential of the brain.

5. The method of claim 1, wherein determining whether the brain is in the state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements comprises:

determining whether the selected frequency component of the waveform of the impedance measurements indicates the brain is in the state indicative of the possibility of a future seizure; and

validating that the brain is in the state indicative of the possibility of a future seizure based on the potential measurements.

6. The method of claim 5, wherein validating that the brain is in the state indicative of the possibility of a future seizure based on the potential measurements comprises determining whether the potential measurements indicate the brain is in the state indicative of the possibility of a future seizure.

7. The method of claim 6, further comprising storing an indicator if the potential measurements do not indicate the brain is in the state indicative of the possibility of a future seizure.

8. The method of claim 1, wherein determining whether the brain is in the state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements comprises:

determining whether the brain is in the state indicative of the possibility of a future seizure based on the potential measurements; and

validating that the brain is in the state indicative of the possibility of a future seizure based on the selected frequency component of the waveform of the impedance measurements.

9. The method of claim 1, further comprising comparing an amplitude of the waveform of the impedance measurements to a predetermined threshold value and determining whether the brain is in the state indicative of the possibility of a future seizure based on the comparison of the amplitude of the waveform of the impedance measurements to the predetermined threshold value.

10. The method of claim 1, wherein determining whether the brain is in the state indicative of the possibility of a future seizure comprises comparing an amplitude of the potential measurements to a predetermined threshold value.

11. The method of claim 1, further comprising comparing a trend in the waveform of the impedance measurements to a template and determining that the brain is in the state indicative of the possibility of a future seizure based on the comparison of the trend to the template.

12. The method of claim 1, wherein determining whether the brain is in the state indicative of the possibility of a future seizure based on the potential measurements comprises comparing a trend in the potential measurements to a template.

13. The method of claim 12, wherein the trend indicates a rate of change of the potential measurements over time.

14. The method of claim 1, further comprising comparing a pattern of the impedance measurements relative to the potential measurements over time to a template and determining whether the brain is in the state indicative of the possibility of a future seizure based on the comparison of the pattern of the impedance measurements relative to the potential measurements over time to the template.

15. The method of claim 1, wherein determining whether the brain is in the state indicative of the possibility of a future seizure comprises comparing the selected frequency component of the waveform of the impedance measurements to a corresponding frequency component of a waveform template.

16. The method of claim 1, wherein determining whether the brain is in the state indicative of the possibility of a future seizure comprises determining a frequency component of a waveform of the potential measurements and comparing the frequency component of the waveform of the potential measurements to a corresponding frequency component of a waveform template.

17. The method of claim 1, further comprising controlling a therapy delivery module to deliver therapy to the patient in response to determining the brain is in the state indicative of the possibility of a future seizure.

18. The method of claim 17, wherein controlling the therapy delivery module to deliver therapy comprises controlling the therapy delivery module to deliver therapy to the patient in response to determining the brain is in the state indicative of the possibility of a future seizure based on one of the selected frequency component of the waveform of the impedance measurements or the potential measurements.

19. The method of claim 17, wherein controlling the therapy delivery module to deliver therapy comprises controlling the therapy delivery module to deliver therapy to the patient in response to determining the selected frequency component of the waveform of the impedance measurements indicates the brain is in the state indicative of the possibility of a future seizure and the potential measurements indicate the brain is in the state indicative of the possibility of a future seizure.

20. The method of claim 1, further comprising generating a notification in response to determining that the brain is in the state indicative of the possibility of a future seizure.

21. The method of claim 1, further comprising measuring, with a sensing module, the impedance of the brain of the patient to generate the impedance measurements by at least measuring the impedance within at least one region of the brain, the region being selected from a group comprising:

a cortex, brainstem, anterior thalamus, ventrolateral thalamus, globus pallidus, substantia nigra pars reticulata, subthalamic nucleus, neostriatum, cingulated gyrus or cingulate gyrus.

22. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain of the patient to generate the potential measurements by at least measuring the potential within at least one region of the brain, the region being selected from a group comprising:

a cortex, brainstem, anterior thalamus, ventrolateral thalamus, globus pallidus, substantia nigra pars reticulata, subthalamic nucleus, neostriatum, cingulated gyms or cingulate gyrus.

23. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain of the patient to generate the potential measurements by at least measuring the potential within a same region of the brain in which the impedance is measured.

24. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain of the patient to generate the potential measurements by at least measuring the potential within a different region of the brain in which the impedance is measured.

25. The method of claim 1, further comprising measuring, with a sensing module, the impedance of the brain of the patient to generate the impedance measurements by at least:

generating an alternating current (ac) stimulation current at a clock frequency;

applying the stimulation current to a brain tissue load to produce a differential input signal;

amplifying the differential input signal in a mixer amplifier to produce an amplified signal;

demodulating the amplified signal in the mixer amplifier at the clock frequency to produce an output signal;

modulating an amplitude of the output signal at the clock frequency to produce a differential feedback signal; and

applying the modulated output signal as a differential feedback signal to the differential input signal via a first feedback path.

26. The method of claim 1, further comprising measuring, with a sensing module, the potential of the brain of the patient to generate the potential measurements by at least:

modulating an amplitude of a differential input signal indicative of the potential of the brain at a clock frequency to produce a modulated signal;

amplifying the modulated signal in a mixer amplifier to produce an amplified signal;

demodulating the amplified signal in the mixer amplifier at the clock frequency to produce an output signal;

modulating an amplitude of the output signal at the clock frequency; and

applying the modulated output signal as a differential feedback signal to the modulated input signal via a first feedback path.

27. A system comprising:

a sensing module configured to measure a potential of a brain of a patient, and measure an impedance of the brain, wherein the impedance of the brain is indicative of a physiological state of the brain; and

a processor coupled to the sensing module, wherein the processor is configured to receive impedance measurements and potential measurements from the sensing module, select a frequency component of a waveform of the impedance measurements from a plurality of frequency components of the waveform of the impedance measurements, and determine whether the brain is in a state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements.

28. The system of claim 27, wherein the sensing module is configured to measure the potential of the brain via at least one of electroencephalography (EEG) or electrocorticography (ECoG).

29. The system of claim 27, wherein the sensing module comprises:

an impedance sensing module configured to measure the impedance of the brain, wherein the processor is configured to receive the impedance measurements from the impedance sensing module; and

a potential sensing module configured to measure the potential of the brain, wherein the processor is configured to receive the potential measurements from the potential sensing module.

30. The system of claim 29, further comprising:

a first set of electrodes coupled to the impedance sensing module; and

a second set of electrodes coupled to the potential sensing module.

31. The system of claim 29, wherein the impedance sensing module and the potential sensing module include common sensing circuitry.

32. The system of claim 27, wherein the sensing module is configured to measure the potential of the brain and measure the impedance of the brain at different times.

33. The system of claim 32, wherein the sensing module is configured to alternate between measuring the potential of the brain and measuring the impedance of the brain.

34. The system of claim 33, wherein the processor is configured to receive alternating potential measurements and impedance measurements from the sensing module and determine whether the brain is in the state indicative of the possibility of a future seizure based on a pattern in the potential measurements and impedance measurements.

35. The system of claim 27, wherein the processor is configured to determine whether the brain is in the state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements by at least:

determining whether the selected frequency component of the waveform of the impedance measurements indicates the brain is in the state indicative of the possibility of a future seizure; and

validating that the brain is in the state indicative of the possibility of a future seizure based on the potential measurements.

36. The system of claim 27, wherein the processor is configured to determine whether the brain is in the state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements by at least:

determining whether the potential measurements indicate the brain is in the state indicative of the possibility of a future seizure; and

validating that the brain is in the state indicative of the possibility of a future seizure based on the selected frequency component of the waveform of the impedance measurements.

37. The system of claim 27, wherein the processor is further configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least comparing an amplitude of the waveform of the impedance measurements to a predetermined threshold value.

38. The system of claim 27, wherein the processor is configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least comparing an amplitude of the potential measurements to a predetermined threshold value.

39. The system of claim 27, wherein the processor is configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least comparing a trend in the impedance measurements to a template.

40. The system of claim 27, wherein the processor is configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least comparing a trend in the potential measurements to a template.

41. The system of claim 27, wherein the sensing module is configured to generate the waveform of the impedance measurements, and wherein the processor is configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least analyzing the selected frequency component of the waveform of the impedance measurements and comparing the selected frequency component of the waveform of the impedance measurements to a corresponding frequency component of a waveform template.

42. The system of claim 27, wherein the sensing module is configured to generate a waveform of the potential measurements, and wherein the processor is configured to determine whether the brain is in the state indicative of the possibility of a future seizure by at least analyzing a frequency component of the waveform of the potential measurements and comparing the frequency component of the waveform of the potential measurements to a corresponding frequency component of a waveform template.

43. The system of claim 27, further comprising a therapy delivery module coupled to the processor, wherein the processor is configured to control delivery of therapy to the patient via the therapy delivery module in response to determining that the brain is in the state indicative of the possibility of a future seizure.

44. The system of claim 27, further comprising a notification device, wherein the processor is configured to activate the notification device in response to determining that the brain is in the state indicative of the possibility of a future seizure.

45. The system of claim 27, further comprising a therapy delivery module coupled to the processor, wherein the processor is configured to control delivery of therapy to the patient via the therapy delivery module in response to determining the brain is in the state indicative of the possibility of a future seizure based on one of the selected frequency component of the waveform of the impedance measurements or the potential measurements.

46. The system of claim 27, wherein the sensing module is configured to measure the impedance and the potential of a same region of the brain.

47. The system of claim 27, wherein the sensing module is configured to measure the potential in a first region of the brain and the impedance in a second region of the brain that is different than the first region.

48. The system of claim 27, wherein the sensing module comprises a chopper-stabilized instrumentation amplifier to measure the impedance of the brain, the instrumentation amplifier comprising:

an alternating current (ac) source configured to generate an (ac) stimulation current at a clock frequency for application to a brain tissue load;

a mixer amplifier coupled to receive a differential input signal from the brain tissue load in response to the stimulation current, wherein the mixer amplifier is configured to amplify the differential input signal to produce an amplified signal and demodulate the amplified signal at the clock frequency to produce an output signal;

a modulator configured to modulate an amplitude of the output signal at the clock frequency; and

a feedback path configured to apply the modulated output signal as a differential feedback signal to the differential input signal.

49. The system of claim 27, wherein the sensing module comprises a chopper-stabilized instrumentation amplifier to measure the potential of the brain, the instrumentation amplifier comprising:

a first modulator configured to modulate an amplitude of a differential input signal indicative of the potential of the brain at a clock frequency to produce a modulated signal;

a mixer amplifier configured to amplify the modulated signal to produce an amplified signal and demodulate the amplified signal at the clock frequency to produce an output signal;

a second modulator configured to modulate an amplitude of the output signal at the clock frequency; and

a feedback path configured to apply the modulated output signal as a differential feedback signal to the modulated input signal.

50. A non-transitory computer-readable medium comprising instructions that, when executed by a programmable processor, cause the programmable processor to:

receive impedance measurements indicative of an impedance of a brain of a patient, wherein the impedance of the brain is indicative of a physiological state of the brain;

receive potential measurements indicative of potential of the brain;

select a frequency component of a waveform of the impedance measurements from a plurality of frequency components of the waveform of the impedance measurements; and

determine whether the brain is in a state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements.

51. The non-transitory computer-readable medium of claim 50, further comprising instructions that, when executed by the programmable processor, cause the processor to control a therapy delivery module to deliver therapy to the patient in response to determining that the brain is in the state indicative of the possibility of a future seizure.

52. The non-transitory computer-readable medium of claim 50, further comprising instructions that, when executed by the programmable processor, cause the processor to determine whether the brain is in the state indicative of a possibility of a future seizure based on the potential measurements and the selected frequency component of the waveform of the impedance measurements by at least determining whether the selected frequency component of the waveform of the impedance measurements indicates the brain is in the state indicative of the possibility of a future seizure and validating the determination based on whether the potential measurements indicates the brain is in the state indicative of the possibility of a future seizure.