Elektrophysiologische Kriterien und klinische Bedeutung von periodischen lateralisierten epileptiformen Entladungen (PLEDs)

Periodic lateralized epileptiform discharges (PLED), an EEG-pattern first described by Chatrian et al. in 1964, are defined by continuous periodic complexes, usually occurring every 1 to 2s and variably consisting of spikes or sharp waves followed by a slow wave. PLEDs characteristically appear in a lateralized fashion over the involved hemisphere, sometimes to a lesser degree in contralateral homologous regions, after an acute unilateral forebrain lesion most often as a consequence of cerebral infarction or tumours. They are often associated with focal motor seizures and status epilepticus and carry a poor prognosis in many patients. This paper presents detailed electrophysiological criteria for PLEDs and discusses the clinical significance of this pattern. Unfortunately, the currently available studies are retrospective and do not provide an accurate estimation of the real incidence of PLEDs, nor do they clearly address several other important and interesting aspects, including the temporal relationship between seizures and PLEDs (and vice versa), the time of appearance and disappearance of the EEG abnormality, the clinical significance of PLEDs (including necessity of antiepileptic drugs) and the underlying pathophysiology. The need for further adequately designed studies is emphasized.