[Differential diagnosis in idiopathic generalized epilepsies with tonic-clonic seizures: assessment of the use of ambulatory EEG and video/EEG monitoring].

The value of long-term cassette EEG (24-EEG) and Video/EEG for differential diagnosis and classification of idiopathic epilepsies with generalised tonic-clonic seizures (GTCS) was evaluated in twenty-eight patients. The analysis of clinical and EEG features allowed proper classification of epileptic syndrome in twenty-two (79%) patients. In twelve cases absences or myoclonic seizures appeared beside GTCS after 1-9 years from epilepsy onset (mean 3.3 yrs). EEG and clinical data allowed to classify epilepsy in nine (75%) of those patients: in six patients as juvenile absence epilepsy and in three as juvenile myoclonic epilepsy. Sixteen patients suffered from GTCS only (mean duration of epilepsy 10.6 years); in thirteen of them (81%) the diagnosis of epilepsy with GTCS on awakening (AGM) could be established. 24-EEG and Video/EEG helped to demonstrate (a) interictal generalized spike/polyspike-wave discharges (SW/PSW) 3-6 Hz not present in routine EEG in 25% of patients, (b) typical circadian distribution of discharges in AGM patients and (c) absences and myoclonic seizures in 32% of patients. Slow spike-wave variants and focal changes in EEG which could suggest secondarily generalized GTCS were the main diagnostic problem.