Neurological event detection tools for implantable medical devices
An implantable device includes one or more electrodes to sense an electrical signal from a brain and a waveform analyzer to identify a half wave in the electrical signal; determine an amplitude and a duration of the half wave; determine if the amplitude satisfies a half wave amplitude criterion defined by a set of amplitude parameters comprising a minimum half wave amplitude and a maximum half wave amplitude; determine if the duration satisfies a half wave duration criterion defined by a set of duration parameters comprising a minimum half wave duration and a maximum half wave duration; and identify the half wave as a qualified half wave when the half wave amplitude criterion and the half wave duration criterion is satisfied. A neurological event may be detected based on one or more qualified half waves and electrical stimulation therapy may be delivered to the brain in response to the detection.
1. An implantable medical device, comprising:
one or more electrodes configured to sense an electrical signal from a patient's brain;
an event detector coupled to the one or more electrodes and configured to obtain the electrical signal sensed by the electrodes, the event detector comprising a waveform analyzer configured to:
identify a half wave in the electrical signal;
determine an amplitude of the half wave and a duration of the half wave;
determine whether the identified half wave has a positive slope or a negative slope;
determine if the amplitude satisfies a half wave amplitude criterion defined by a set of amplitude parameters comprising a minimum half wave amplitude and a maximum half wave amplitude, wherein, in a case of a positive-slope half wave, the half wave amplitude criterion is defined by a first set of amplitude parameters, and in a case of a negative-slope half wave, the half wave amplitude criterion is defined by a second set of amplitude parameters that is different from the first set of amplitude parameters;
determine if the duration satisfies a half wave duration criterion defined by a set of duration parameters comprising a minimum half wave duration and a maximum half wave duration, wherein, in a case of a positive-slope half wave, the half wave duration criterion is defined by a first set of duration parameters, and in a case of a negative-slope half wave, the half wave duration criterion is defined by a second set of duration parameters that is different from the first set of duration parameters; and
identify the half wave as a qualified half wave when each of the half wave amplitude criterion and the half wave duration criterion is satisfied; and
a processor configured to determine, based on a count of the number of qualified half waves occurring within a time window and a half wave count criterion, whether the electrical signal sensed from the patient's brain includes electrographic activity indicative of epileptiform activity.
2. The device of claim 1 , wherein the half wave amplitude criterion is satisfied when the amplitude of the half wave is between the minimum half wave amplitude and the maximum half wave amplitude.
3. The device of claim 1 , wherein the half wave duration criterion is satisfied when the duration of the half wave is between the minimum half wave duration and the maximum half wave duration.
4. The device of claim 1 , wherein the processor is configured to:
determine the count of the number of qualified half waves occurring within the time window;
compare the count to the half wave count criterion; and
determine the electrical signal sensed from the patient's brain includes electrographic activity indicative of epileptiform activity when the count exceeds the half wave count criterion.
5. The device of claim 4 , wherein the event detector is configured to output an event detection upon determining the electrical signal sensed from the patient's brain includes electrographic activity indicative of epileptiform activity.
6. The device of claim 5 , further comprising a stimulation subsystem configured to receive the event detection from the event detector and to output an electrical stimulation to the one or more electrodes in response to the event detection.
7. The device of claim 1 , wherein the epileptiform activity corresponds to one of an epileptic seizure or a seizure onset.
8. The device of claim 1 , wherein:
the first set of amplitude parameters includes a positive-slope minimum half wave amplitude of between 0 and 1022 units of amplitude, and a positive-slope maximum half wave amplitude of between 1 and 1023 units of amplitude; and
the first set of duration parameters includes a positive-slope minimum half wave duration of between 0 and 386 ms, and a positive-slope maximum half wave duration of between 4 and 400 ms.
9. The device of claim 1 , wherein
the second set of amplitude parameters is a negative-slope minimum half wave amplitude of between 0 and 1022 units of amplitude, and a negative-slope maximum half wave amplitude of between 1 and 1023 units of amplitude; and
the second set of duration parameters comprises a negative-slope minimum half wave duration of between 0 and 386 ms, and a negative-slope maximum half wave duration of between 4 and 400 ms.
10. A method of an implanted medical device, the method comprising:
identifying, with a waveform analyzer of the implanted medical device, a half wave in an electrical signal sensed from a brain;
determining, with the waveform analyzer, an amplitude of the half wave and a duration of the half wave;
determining, with the waveform analyzer, whether the identified half wave has a positive slope or a negative slope;
determining, with the waveform analyzer, if the amplitude satisfies a half wave amplitude criterion defined by a set of amplitude parameters comprising a minimum half wave amplitude and a maximum half wave amplitude, wherein, in a case of a positive-slope half wave, the half wave amplitude criterion is defined by a first set of amplitude parameters, and in a case of a negative-slope half wave, the half wave amplitude criterion is defined by a second set of amplitude parameters that is different from the first set of amplitude parameters;
determining, with the waveform analyzer, if the duration satisfies a half wave duration criterion defined by a set of duration parameters comprising a minimum half wave duration and a maximum half wave duration, wherein, in a case of a positive-slope half wave, the half wave duration criterion is defined by a first set of duration parameters, and in a case of a negative-slope half wave, the half wave duration criterion is defined by a second set of duration parameters that is different from the first set of duration parameters;
identifying, with the waveform analyzer, the half wave as a qualified half wave when each of the half wave amplitude criterion and the half wave duration criterion is satisfied; and
determining, with the waveform analyzer, based on a count of the number of qualified half waves occurring within a time window and a half wave count criterion, whether the electrical signal sensed from the brain includes electrographic activity indicative of epileptiform activity.
11. The method of claim 10 , wherein the half wave amplitude criterion is satisfied when the amplitude of the half wave is between the minimum half wave amplitude and the maximum half wave amplitude.
12. The method of claim 10 , wherein the half wave duration criterion is satisfied when the duration of the half wave is between the minimum half wave duration and the maximum half wave duration.
13. The method of claim 10 , wherein determining whether the electrical signal sensed from brain includes electrographic activity indicative of epileptiform activity comprises:
determining the count of the number of qualified half waves occurring within the time window;
comparing the count to the half wave count criterion; and
determining the electrical signal sensed from the brain includes electrographic activity indicative of epileptiform activity when the count exceeds the half wave count criterion.
14. The method of claim 13 , further comprising outputting an event detection upon determining the electrical signal sensed from the brain includes electrographic activity indicative of epileptiform activity.
15. The method of claim 14 , further comprising outputting an electrical stimulation to the brain in response to the event detection.
16. The method of claim 10 , wherein the epileptiform activity corresponds to one of an epileptic seizure or a seizure onset.
17. The method of claim 10 , wherein:
the first set of amplitude parameters includes a positive-slope minimum half wave amplitude of between 0 and 1022 units of amplitude, and a positive-slope maximum half wave amplitude of between 1 and 1023 units of amplitude; and
the first set of duration parameters includes a positive-slope minimum half wave duration of between 0 and 386 ms, and a positive-slope maximum half wave duration of between 4 and 400 ms.
18. The method of claim 10 , wherein
the second set of amplitude parameters is a negative-slope minimum half wave amplitude of between 0 and 1022 units of amplitude, and a negative-slope maximum half wave amplitude of between 1 and 1023 units of amplitude; and
the second set of duration parameters comprises a negative-slope minimum half wave duration of between 0 and 386 ms, and a negative-slope maximum half wave duration of between 4 and 400 ms.