Method of wavelet transform in neurology: analysis of time and frequency characteristics of typical and atypical discharges of nonconvulsive epilepsy

Timefrequency dynamics and spatial characteristics of dischar ges of different types in patients with nonconvulsive epilepsy (n=23) were investigated. Modified wavelet transform was used for the analysis. In patients (n=11) with the diagnosis of childhood absence epilepsy, juvenile absence epilepsy or juveni le mioclonic epilepsy, the timefrequency dynamics of spikewa ve discharges were identical. Typical spikewave discharge arose in the frontal cortex with the short period of maximal frequency (5–6 Hz). The further frequency was 3–3.5 Hz with periodical (about 1 s) fluctuations. In another group of patients (n=12) with the diagnosis of nonconvulsive epilepsy the discharges of several types were observed, and they differed in duration, time frequency dynamics and activity localization with maximal amplitude in the cortex. Atypical discharges were different from typical ones: they had less ordered timefrequency structure and lacked the high frequency period in the frontal cortex. In some patients typical and atypical discharges, or two different forms of atypical discharges could be seen on the same EEG record. The obtained data show that the discharges’ timefrequency analysis with the help of the modified wavelet transform can be used for the classification of discharges of different types and are of value for differential diagnosis of nonconvulsive epilepsy.