MISLEADING ASPECTS OF THE STANDARD EEG IN JUVENILE MYOCLONIC EPILEPSY- RETROSPECTIVE STUDY OF 56 CONSECUTIVE NEWLY REFERRED CASES

Atypical clinical and/or EEG presentation may complicate the diagnosis of juvenile myoclonic epilepsy (JME). To assess the sensitivity of a standard EEG recording, we retrospectively evaluated the EEG performed at their first referral in 56 consecutive JME patients first seen bet ween 1986 and 1992 (26 M, 30 F, aged 12-53, mean 24.4, with onset of J ME at age 10-33, mean 14.3). The diagnosis had been made in none of th ese patients prior to referral, and was often confirmed only during fo llow-up. A 20-minute standard EEG was recorded, including hyperventila tion (HV) and intermittent light stimulation (ILS). This EEG was norma l in 15 cases (27%), showing aspecific or misleading changes in II cas es (20%) and typical changes in only 30 cases (54%). The baseline EEG was normal in 25 (45%), atypical in 11 (20%), and typical for JME in o nly 20 (35%). HV and ILS yielded 37 and 39 normal, 10 and 7 aspecific and 9 and 10 specific findings, respectively. A single standard EEG wi thout activation may thus be inconclusive or misleading for the diagno sis of JME in more than 50% of newly referred patients.