Abstracts

RATIONALE: Several type of repetitive electroencephalographic discharges without clinical significance have already been reported. This is a rare nonepileptogenic epileptiform activity of unknown pathophysiology which might be misdiagnosed as epilepsy. Different EEG patterns have been described according to frequency ranges, morphology and distribution of the discharges. Here we report 4 additional patients considered as epileptic because of persistent epileptiform EEG activity.
METHODS: A diagnosis of absence seizures was made in the first case, at the age of 9 years and treated with antiepileptic drug continued for 8 years. In the second case, status epilepticus was suspected after a typical syncope. In the third case, antiepileptic drug was given for 7 years after a single provoked convulsive seizure. In the last case, typical migrainous attacks was misdiagnosed as epilepsy.
RESULTS: In all 4 cases, rythmic epileptiform discharges have been recorded on the EEG. These discharges consisted in frequent trains of rythmic slow activity (range frequencies from 3 to 5 Hz) lasting 5 to 30 seconds, disappearing with eyes opening and during intermittent light stimulation. Such EEG abnormalities occurred without any clinical symptoms and predominated on the left temporo-occipital region in the first case, the right temporo-occipital region in the second patient, the right parietal region in the third and left fronto-temporal region in the last case. Anti-epileptic drugs were finally interrupted. Further EEG recordings showed the same persistent epileptiform activity in all patients, without any clinical epileptic symptoms.
CONCLUSIONS: These epileptiform discharges must be recognized as benign EEG variant without relationship with epilepsy. Our cases are probably a variant of subclinical rythmic electroencephalographic discharges of adults (SREDA).