Seizure sensing and detection using an implantable device

• US 20070016094A1
• Filed: 10/25/2004
• Published: 01/18/2007
• Est. Priority Date: 06/28/2001
• Status: Active Grant

• Current Assignee: Neuropace Inc.
• Original Assignee: Neuropace Inc.
• Inventors: Pless, Benjamin
• Granted Patent: US 7,813,793 B2
• Time in Patent Office: Days
• US Class Current: 600/544
• CPC Class Codes: A61B 5/291 for electroencephalography [EEG]
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/4094 Diagnosing or monitoring seizure diseases, e.g. epilepsy
• CPC Class Codes: A61B 5/6868 Brain
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7242 using integration
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• 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 1/36064 Epilepsy

Abstract

A system and method for detecting and predicting neurological events with an implantable device uses a relatively low-power central processing unit in connection with signal processing circuitry to identify features (including half waves) and calculate window-based characteristics (including line lengths and areas under the curve of the waveform) in an electrographic signal received from a patient'"'"'s brain. The features and window-based characteristics are combinable in various ways according to the invention to detect and predict neurological events in real time, enabling responsive action by the implantable device.

Claims

1. An implantable device for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain, the device comprising:

an implantable control module;

a central processing unit located within the control module; and

a detection subsystem located within the control module and comprising a waveform analyzer having a window-based analysis unit and a feature-based analysis unit.

2. The implantable device of claim 1, wherein the detection subsystem performs a first portion of an event detection procedure, and the central processing unit performs a second portion of the event detection procedure.

3. The implantable device of claim 1, wherein the central processing unit and the detection subsystem are enclosed within a housing, and wherein the housing is implanted in the patient.

4. The implantable device of claim 3, wherein the housing is implanted intracranially in the patient.

5. The implantable device of claim 1, wherein the neurological event comprises an epileptic seizure, an onset of an epileptic seizure, a precursor to an epileptic seizure, an episode of a movement disorder, an onset of an episode of a movement disorder, a precursor to an episode of a movement disorder, a migraine headache, an onset of a migraine headache, a precursor to a migraine headache, an episode of pain, an onset of an episode of pain, a precursor to an episode of pain, an episode of depression, an onset of an episode of depression, or a precursor to an episode of depression.

6. The implantable device of claim 1, wherein the neurological event comprises an event predictive of an episode of clinical symptoms selected from the group consisting of an epileptic seizure, an episode of a movement disorder, a migraine headache, an episode of pain, and an episode of depression.

7. The implantable device of claim 1, wherein the detection subsystem comprises at least one electronics module.

8. The implantable device of claim 1, wherein the feature-based analysis unit comprises a wave morphology analysis unit.

9. An implantable device for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain, the device comprising:

an implantable control module;

a detection subsystem located within the control module and adapted to identify at least one feature in the electrical signal and calculate at least one window parameter in the electrical signal; and

a central processing unit located within the control module and adapted to analyze the at least one feature and the at least one window parameter, and to initiate an action in accordance therewith.

10. An implantable device for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain, the device comprising:

an implantable control module;

a central processing unit located within the control module; and

a detection subsystem located within the control module;

wherein the detection subsystem performs at least a portion of a detection task without the use of the central processing unit, thereby allowing the central processing unit to remain in a relatively inactive mode at least part of the time.

11. A method for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain with an implantable device, the method comprising the steps of:

receiving the electrical signal with an electrode pair;

processing the electrical signal with a detection subsystem, wherein the detection subsystem is adapted to identify at least one feature in the electrical signal and calculate at least one window parameter in the electrical signal; and

causing the implantable device to perform an action in accordance with an indication from the detection subsystem.

12. The method for detecting a neurological event of claim 11, wherein the processing step comprises the steps of:

sampling the electrical signal to create a sampled digital signal;

identifying a feature in the sampled digital signal with a wave morphology analysis unit; and

calculating a window parameter in the sampled digital signal with a window analysis unit.

13. The method for detecting a neurological event of claim 12, wherein the calculating step comprises the step of computing a line length function.

14. The method for detecting a neurological event of claim 13, further comprising the step of transforming the sampled digital signal prior to computing the area function.

15. The method for detecting a neurological event of claim 12, wherein the causing step comprises the steps of:

processing the feature and the window parameter to determine whether to set a detection flag;

if the detection flag is set, performing an action in accordance with the detection flag.

16. A method for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain with an implantable device, the method comprising the steps of:

receiving a first electrical signal and a second electrical signal from a plurality of electrodes;

processing the electrical signals with a detection subsystem to obtain a first detection channel output and a second detection channel output;

combining the first detection channel output and the second detection channel output to obtain an event detector output; and

causing the implantable device to perform an action in accordance with the event detector output.

17. A method for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain with an implantable device, the method comprising the steps of:

receiving the electrical signal with an electrode pair;

processing the electrical signal;

converting the electrical signal into a digital signal;

performing a feature extraction operation on the digital signal;

performing a window calculation operation on the digital signal;

analyzing a result from the feature extraction operation;

analyzing a result from the window calculation operation; and

performing an action in accordance with the result from the feature extraction operation and the result from the window calculation operation.

18. A method for detecting a neurological event by analyzing an electrical signal from a patient'"'"'s brain with an implantable device, the device having a processor and a detection subsystem, the method comprising the steps of:

causing the processor to enter a low-power mode;

measuring a feature characteristic of the electrical signal with the detection subsystem;

measuring a window characteristic of the electrical signal with the detection subsystem;

causing the processor to exit the low-power mode;

analyzing the feature characteristic and the window characteristic with the processor; and

performing an action in accordance with the feature characteristic and the window characteristic.

19. The method for detecting a neurological event of claim 18, wherein the low-power mode is characterized by relative inactivity.