Age-related changes of cortical excitability in subjects with sleep-enhanced centrotemporal spikes: a somatosensory evoked potential study

Middle-latency somatosensory evoked potentials (SEPs) of particularly large amplitude (giant) have been reported in subjects with benign childhood epi lepsy with centrotemporal spikes (BECT) and in normal children, which usual ly show significant age-related changes. However, the mechanisms by which a ge modifies the appearance of centrotemporal spikes and giant SEPs in these children, are not known. The characteristics of SEPs were studied in a gro up of 18 subjects (10 males and 8 females, aged 7.1-17.2 years) with sleep- enhanced centrotemporal spikes, with or without BECT and the results were c ompared with those obtained from a group of age-matched normal controls. Gi ant SEPs were recorded in 6 subjects and, in 3 of these, EEG spikes evoked by hand tapping were obtained also. No subjects with giant SEPs were found in subjects older than 12 years, and an age-related decrease in amplitude o f giant SEPs as this age approached was observed. Moreover, at repeated SEP recordings, a clear trend towards a more important reduction in amplitude of giant SEPs over the temporal and parietal than over the central regions was evident. The study of EEG spikes evoked by hand tapping showed a striki ng similarity between the averaged evoked spikes and the main negative comp onent of giant SEPs. It was also possible to observe that the spike negativ e peak recorded over the central areas always preceded the same component r ecorded over the parietal and temporal areas by 5-15 ms. Our study seems to support the idea that giant SEPs in subjects with centrotemporal spikes ar e generated by a complex mechanism different from that at the basis of the normal N60 component of SEPs; they also show peculiar age-related modificat ions which can be interpreted in terms of maturational changes of brain exc itability/inhibition and probably constitute a tool for monitoring the clin ical course of BECT, when present. (C) 2000 Elsevier Science Ireland Ltd. A ll rights reserved.