Differentiation of typical absence seizures in epileptic syndromes. A video EEG study of 224 seizures in 20 patients.

This is a comparative video-electroencephalographic (EEG) study of typical absence seizures in 4 epileptic syndromes. In 20 patients, 224 absences were recorded and analysed. Significant clinical and EEG differences were found in the seizure patterns of childhood absence epilepsy (CAE), juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy with absences (JMEA) and myoclonic absence epilepsy (MAE). Clinically, CAE demonstrated more severe impairment of consciousness than JAE while, in JMEA, ictal manifestations were frequently mild and difficult to detect. In the latter, the adolescent patient usually continued his activity, was able to perform even mathematical calculations and often his speech was not disturbed. In children with JMEA, impairment of consciousness was more apparent and sometimes severe. Automatisms occurred in all 4 epileptic syndromes and were proportional to the severity of the demonstrated impairment of consciousness, being rare in JMEA but frequent in CAE and JAE. Expressive speech and overbreathing usually persisted for 1-2 s after the onset of the EEG ictal discharge in CAE. It was less disturbed in JAE where in some absence seizures, interrupted speech and overbreathing were restored during the ictus. A characteristic clinical manifestation of CAE was opening of the eyes in all absence seizures within 1.8 +/- 0.6 s (max. 2.5 s) from the onset of the EEG paroxysms. This early eye-opening behaviour was not observed in JMEA. In MAE, rhythmical myoclonic jerks at 3 Hz make the diagnosis unmistakable. Myoclonic jerks were extremely rare in the absences of JMEA, although all patients had independent myoclonic jerks on awakening. The ictal EEG discharge was longer in JAE (mean 16.3 +/- 7.1 s) than in CAE (12.4 +/- 2.1 s) or JMEA (6.6 +/- 4.2 s). The opening phase of the EEG paroxysms did not show significant differences in CAE, JAE and JMEA but significant changes were found in their initial and terminal ictal phases. In JMEA, the spike-multiple spike-slow wave complexes were not rhythmic and frequently demonstrated variable spike-slow wave relationships. Ictal discharge fragmentations and spike-wave discharges looking like compressed capital Ws were often seen and are characteristic of JMEA. seen and are characteristic of JMEA. Absence seizures demonstrated a more severe impairment of expressive rather than receptive speech, irrespective of differences between syndromes. Evoked as well as spontaneous automatisms occurred in the same patients.(ABSTRACT TRUNCATED AT 400 WORDS)