Method and apparatus for detection of nervous system disorders

• US 7,761,146 B2
• Filed: 12/12/2006
• Issued: 07/20/2010
• Est. Priority Date: 04/21/2006
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Werder, Jonathan C., Drew, Touby A., Carlson, David L, Panken, Eric J
• Primary Examiner(s): Layno; Carl H
• Assistant Examiner(s): GHAND, JENNIFER LEIGH-STEWAR
• Application Number:
  US11/609,432
• Publication Number:
  US 20070249955A1
• Time in Patent Office: 1,316 Days
• Field of Search: 600/544, 600/545, 607/45
• US Class Current: 600/544
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• 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 1/36082 Cognitive or psychiatric applications, e.g. dementia or Alzheimer's disease
• CPC Class Codes: G16H 20/30 relating to physical therapies or activities, e.g. physiotherapy, acupressure or exercising
• CPC Class Codes: G16H 40/63 for local operation
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 50/20 for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

Systems and methods for detecting and/or treating nervous system disorders, such as seizures. Certain embodiments of the invention relate generally to implantable medical devices (IMDs) adapted to detect and treat nervous system disorders in patients with an IMD. Certain embodiments of the invention include detection of seizures based upon comparisons of long-term and short-term representations of physiological signals. Other embodiments include prediction of seizure activity based upon analysis of physiological signal levels. An embodiment of the invention monitors the quality of physiological signals, and may be able to compensate for signals of low signal quality. A further embodiment of the invention includes detection of seizure activity following the delivery of therapy.

Claims

1. A method of detecting a neurological event following delivery of stimulation therapy, the method comprising:

detecting a first neurological event using a first detection algorithm;

delivering stimulation therapy in response to detecting the first neurological event;

imposing a time delay before (1) detecting a subsequent neurological event using the first detection algorithm, and/or (2) delivering subsequent stimulation therapy based on the first detection algorithm; and

detecting a post-stimulation neurological event during the time delay using a second detection algorithm different than the first detection algorithm, the second detection algorithm comprising

initializing a post-stimulation detection counter, C, to an initial value, C₀,

acquiring a stream of EEG signal data values following the delivery of the stimulation therapy,

comparing the signal data values to a level cutoff,

decrementing C by a decrement amount if a given data value is below the level cutoff,

incrementing C by an increment amount if a given data value is equal to or exceeds the level cutoff,

comparing C to a post-stimulation detection threshold, PS_th, and

detecting the post-stimulation neurological event during the time delay if C equals or exceeds PS_th.

2. The method of claim 1 wherein the level cutoff is determined from a long-term representation of EEG signal data.

3. The method of claim 2 wherein the long-term representation is at least partially based on pre-stimulation EEG signal data values.

4. The method of claim 3 wherein the long-term representation is based on both pre-stimulation and post-stimulation data values.

5. The method of claim 3 wherein the long-term representation of EEG signal data is determined by updating a recent pre-stimulation value with newly acquired post-stimulation data values.

6. The method of claim 2 wherein the long-term representation of EEG signal data is a long-term average, LTA.

7. The method of claim 2 wherein the long-term representation is multiplied by a scale factor to determine the level cutoff.

8. The method of claim 7 wherein the scale factor is user-selectable.

9. The method of claim 7 wherein the scale factor is between about 10 and 30.

10. The method of claim 1 wherein the post-stimulation neurological event is detected when C equals or exceeds PS_th for a post-stimulation duration.

11. The method of claim 10 wherein a specified number of consecutive values of C equals or exceeds PS_th for the post-stimulation duration.

12. The method of claim 10 wherein a predetermined percentage of values of C equals or exceeds PS_th for the post-stimulation duration.

13. The method of claim 1 further comprising setting C equal to a floor, C_FL, if the value of C drops below C_FL as a result of decrementing C.

14. The method of claim 1 further comprising delivering therapy in response to detecting the post-stimulation neurological event.

15. The method of claim 14 wherein the therapy delivered in response to detecting the post-stimulation neurological event is different from the stimulation therapy previously delivered.

16. The method of claim 1, wherein detecting the post-stimulation neurological event during the time delay comprises redetecting the first neurological event.

17. A non-transitory computer-readable medium programmed with instructions for performing a method of detecting a neurological event following delivery of stimulation therapy, the medium comprising instructions for causing a programmable processor to:

detect a first neurological event using a first detection algorithm;

deliver stimulation therapy in response to detecting the first neurological event;

impose a time delay before (1) detecting a subsequent neurological event using the first detection algorithm, and/or (2) delivering subsequent stimulation therapy based on the first detection algorithm; and

detecting a post-stimulation neurological event during the time delay using a second detection algorithm different than the first detection algorithm, the second detection algorithm comprising

initialize a post-stimulation detection counter, C, to an initial value, C₀,

acquire a stream of EEG signal data values following the delivery of the stimulation therapy,

compare the signal data values to a level cutoff,

decrement C by a decrement amount if a given data value is below the level cutoff,

increment C by an increment amount if a given data value is equal to or exceeds the level cutoff,

compare C to a post-stimulation detection threshold, PS_th, and

detect the post-stimulation neurological event during the time delay if C equals or exceeds PS_th.

18. A method of detecting a neurological event following delivery of stimulation therapy, the method comprising:

detecting a first neurological event using a first detection algorithm;

delivering stimulation therapy in response to detecting the first neurological event;

imposing a time delay before (1) detecting a subsequent neurological event using the first detection algorithm, and/or (2) delivering subsequent stimulation therapy based on the first detection algorithm;

detecting a post-stimulation neurological event during the time delay using a second detection algorithm different than the first detection algorithm, the second detection algorithm comprising

initializing a post-stimulation detection counter, C, to an initial value, C_o, acquiring a stream of EEG signal data values following the delivery of the stimulation therapy,

comparing the signal data values to a level cutoff,

decrementing C by a decrement amount if a given data value is below the level cutoff,

incrementing C by an increment amount if a given data value is equal to or exceeds the level cutoff,

comparing C to a post-stimulation detection threshold, PS_th, and

detecting the post-stimulation neurological event during the time delay if C equals or exceeds PS_th; and

delivering therapy during the time delay in response to detecting the post-stimulation neurological event.

19. The method of claim 18 wherein the level cutoff is determined from a long-term representation of EEG signal data.

20. The method of claim 18 wherein the post-stimulation neurological event is detected when C equals or exceeds PS_th for a post-stimulation duration.

21. The method of claim 18 further comprising setting C equal to a floor, C_FL, if the value of C drops below C_FL as a result of decrementing C.

22. The method of claim 18 wherein detecting the post-stimulation neurological event during the time delay comprises redetecting the first neurological event.