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|Epileptic brain signal analysis
Detecting epileptic seizures from long-term recordings
|An example of an epileptic spike-and-wave discharge
is a disease in which the electrical activity of the brain (EEG) is
somewhat distorted. Usually the EEG looks normal for the most of the
time but sometimes kind of "electrical storms" occur in the
brain. These are often associated by visible symptoms in patient. In
mild cases the patient is simply "absent" for a couple of seconds and
in more severe cases the patient falls and has cyclic convulsions.
The suspicion of epilepsy needs to be confirmed with EEG measurements.
A normal 30 minute laboratory recording might reveal epileptic activity
in the EEG with proper stimulus, e.g. with flashing lights but
usually a more long-term recording is needed. The visual analysis of
these long-term recordings is tedious and time-consuming for the EEG
experts. Computerized EEG analysis can help here to pinpoint the events
of interest in the EEG to the expert thus saving him a lot of time.
Our epileptic EEG analysis methods aimed at detecting epileptic
spikes and epileptic seizures form the EEG recordings. The detection of
spikes is based on an adapted version of FIR-Median Hybrid filters
developed in the Department. The detection of seizures is a more
complicated process. The signal is first segmented to variable size
segments based on the signal content. Several time and frequency domain
features are calculated form these segments. The resulting feature
vector is compared to a library of feature vectors representing an EEG
class which has been classified by EEG experts. The closest mach is
chosen as the class of the segment and the occurrence of epileptic
class segments is reported to the clinicians.
The epilepsy signal analysis studies were performed in co-operation
with the departments of Clinical Neurophysiology and Neurology in
Tampere University Hospital. Some sample EEG data is provided for
research purposes in our public FTP site, but note that you need and expert in EEG to actually understand what is going on in these recordings.
International League Against Epilepsy