Seizure prediction

Patent metadata

Field	Value
Publication number	US-9788750-B2
Application number	US-79905107-A
Country	US
Kind code	B2
Filing date	Apr 30, 2007
Priority date	Apr 30, 2007
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

Seizure prediction systems and methods include measuring impedance within a brain of a patient to determine whether the brain is in a state indicative of a possibility of an onset of a seizure. In some embodiments, the measured impedance is compared to a predetermined threshold in order to determine whether the brain is in a state indicative of a possibility of a seizure. In other embodiments, a trend of the impedance measurements is correlated to a template. In other embodiments, a frequency component of a waveform of the impedance measurement amplitudes over time is correlated to frequency components of a template waveform. Upon detecting a state in which a seizure is likely to occur, a seizure indicator may be generated, which, in some embodiments, may be used to activate therapy delivery to the patient or, in other embodiments, activate an alarm.

First claim

The invention claimed is:

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;
determining, with the processor, a trend in the impedance measurements over time;
determining, with the processor, that the brain is in a state indicative of a possibility of a future seizure based on the trend; and
controlling, with the processor, delivery of therapy to the patient based on determining that the brain is in the state indicative of the possibility of the future seizure.

2. The method of claim 1 , further comprising measuring the impedance of the brain of the patient with an impedance sensing module, wherein measuring the impedance of the brain of the patient comprises delivering a stimulation current in a range of about 500 nanoamps to about 10 microamps across tissue in one or more regions of the brain of the patient.

3. The method of claim 1 , further comprising, with the processor, comparing an amplitude of at least one of the impedance measurements to a predetermined threshold and determining that the brain is in the state indicative of the possibility of the future seizure based on the comparison.

4. The method of claim 3 , wherein comparing the amplitude of the at least one of the impedance measurements to the predetermined threshold value comprises comparing an average amplitude of a plurality of the impedance measurements over a period of time to the predetermined threshold value.

5. The method of claim 1 , further comprising:
with the processor, comparing the trend to a template; and
based on the comparison of the trend to the template, determining the trend substantially correlates to the template, wherein determining that the brain is in the state indicative of the possibility of the future seizure comprises determining that the brain is in the state indicative of the possibility of a future seizure based on determining the trend substantially correlates to the template.

6. The method of claim 5 , wherein determining the trend substantially correlates to the template comprises determining a first frequency component of the trend substantially correlates to a second frequency component of the template.

7. The method of claim 1 , wherein the trend indicates a rate of change of the impedance measurements over time.

8. The method of claim 1 , wherein controlling delivery of therapy comprises at least one of controlling delivery of a pharmaceutical agent or controlling delivery of electrical stimulation to tissue of the patient.

9. The method of claim 1 , further comprising, with the processor, controlling the therapy to inhibit an onset of the future seizure.

10. The method of claim 1 , further comprising, with the processor, controlling the therapy to reduce severity or duration of the future seizure.

11. The method of claim 1 , wherein the state indicative of the possibility of a future seizure is a first state, the method further comprising, with the processor, controlling the therapy to return the brain to a second state indicative of a lower possibility of the future seizure than the first state.

12. The method of claim 1 , further comprising measuring the impedance of the brain of the patient with an impedance sensing module, wherein measuring the impedance comprises measuring a complex impedance over at least one frequency.

13. The method of claim 12 , wherein the at least one frequency is in a range of approximately 1 kilohertz to approximately 100 kilohertz.

14. The method of claim 13 , wherein the at least one frequency is in a range of approximately 4 kilohertz to approximately 16 kilohertz.

15. The method of claim 1 , further comprising measuring the impedance of the brain of the patient with an impedance sensing module, wherein measuring the impedance of the brain of the patient comprises measuring the impedance within at least two regions of the brain.

16. The method of claim 15 , wherein the at least two regions are 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.

17. The method of claim 1 , further comprising measuring the impedance of the brain of the patient with an impedance sensing module, wherein measuring the impedance of the brain of the patient comprises measuring the impedance within at least one of a cortex, brainstem, anterior thalamus, ventrolateral thalamus, globus pallidus, substantia nigra pars reticulata, subthalamic nucleus, neostriatum, cingulated gyrus or cingulate gyrus.

18. The method of claim 1 , further comprising, with the processor, generating a notification based on determining that the brain is in the state indicative of the possibility of the future seizure.

19. The method of claim 1 , further comprising measuring the impedance of the brain of the patient with an impedance sensing module, wherein measuring the impedance of the brain of the patient comprises:
generating an alternating current (ac) stimulation current at a frequency;
applying the stimulation current to a brain tissue load to produce an input signal;
amplifying the input signal to produce an amplified signal;
demodulating the amplified signal at the frequency to produce an output signal;
modulating an amplitude of the output signal at the frequency to produce a feedback signal; and
applying the feedback signal to the input signal via a first feedback path.

20. The method of claim 19 , wherein the input signal comprises a differential input signal.

21. A system comprising:
an impedance sensing module configured to measure an impedance of a brain of a patient, and generate impedance measurements indicative of the impedance of the brain, wherein the impedance of the brain is indicative of a physiological state of the brain;
a processor coupled to the impedance sensing module, wherein the processor is configured to receive impedance measurements from the impedance sensing module, determine a trend in the impedance measurements over time, and determine that the brain is in a state indicative of a possibility of a future seizure based on the trend; and
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 the future seizure.

22. The system of claim 21 , wherein the therapy comprises at least one of delivery of a pharmaceutical agent or electrical stimulation.

23. The system of claim 21 , wherein the state indicative of the possibility of the future seizure is a first state, and wherein the processor is configured to control the therapy to return the brain to a second state indicative of a lower possibility of the future seizure than the first state.

24. The system of claim 21 , wherein the impedance sensing module is configured to deliver a stimulation current in a range of about 500 nanoamps to about 10 microamps across tissue in one or more regions of the brain of the patient to measure the impedance.

25. The system of claim 21 , wherein the processor is further configured to compare an amplitude of at least one of the impedance measurements to a predetermined threshold and dete

Assignees

• Denison Timothy J
• Santa Wesley A
• Medtronic Inc

Inventors

• Denison Timothy J
• Santa Wesley A

Classifications

• A61B5/7228

  Signal modulation applied to the input signal sent to patient or subject; Demodulation to recover the physiological signal · CPC title

• A61N1/36025

  for treating a mental or cerebral condition · CPC title

• A61B5/4839

  combined with drug delivery · CPC title

• A61B5/053 Primary

  Measuring electrical impedance or conductance of a portion of the body · CPC title

• A61B5/4094

  Diagnosing or monitoring seizure diseases, e.g. epilepsy · CPC title