[Functional relationship between central and peripheal motor signals. Use of averaging methods in epileptic problems...

For epileptic seizures with low-frequent and mild myoclinic components the existence of correlations between myoclonic and electroencephalographic activity is investigated. The method used is comparable to the evoked potential technique. The summation procedure is triggered by the occurrence of a pre-defined pattern in the peripheral recordings (EMG or acceletrometer) rather than by an external stimulus: 'Jerk-locked averaging' (JLA). Due to the small number of events it is necessary to control the validity of the results. For this aim, confidence intervals for the average signals are calculated. In three cases EEG-correlates have been found two of them showing spike-wave complexes in the EEG. The latency between the first positive spike and myoclonic activity was 12-14 ms and 22 ms, respectively. In the third case no spike pattern is found. JLA, however, shows a phase-locked relation between EEG and muscle activity. In order to interpret the findings different models of neuronal pathways are discussed. According to other studies a latency of 22 ms fits in with the concept of pyramidal activation, whereas latencies smaller than 15 ms are supposed to have subcortical origin spreading simultaneously toward cortex and subcortical efferent structures.