Abstract
Purpose: The aim of this study is to elucidate the clinical and neurophysiological
characteristics of the myoclonic, myoclonic–astatic, or astatic seizures in patients
with myoclonic–astatic epilepsy (MAE) of early childhood, and to discuss on the nosology
of this unique epileptic syndrome.Subjects: The subjects included 30 patients, who
fulfilled the following modified International League Against Epilepsy (ILAE) criteria
for MAE, and whose main seizures were captured by video-electroencephalographs (EEG)
or polygraphs. The modified ILAE criteria includes: (1) normal development before
onset of epilepsy and absence of organic cerebral abnormalities; (2) onset of myoclonic,
myoclonic–astatic or astatic seizures between 7 months and 6 years of age; (3) presence
of generalized spike- or polyspike-wave EEG discharges at 2–3 Hz, without focal spike discharges; and (4) exclusion of severe and benign myoclonic
epilepsy (SME, BME) in infants and cryptogenic Lennox–Gastaut syndrome based on the
ILAE definitions.
Results: The seizures were investigated precisely by video-EEG (n=5), polygraph (n=2), and video-polygraph (n=23), which identified myoclonic seizures in 16 cases (myoclonic group), atonic seizures,
with or without preceding minor myoclonus, in 11 cases (atonic group), and myoclonic–atonic
seizures in three cases. All patients had a history of drop attacks, apart from ten
patients with myoclonic seizures. Myoclonic seizures, involving mainly the axial muscles
were classified into those with mild intensity not sufficient to cause the patients
to fall (n=10) and those that are stronger and sufficient to cause astatic falling due to flexion
of the waist or extension of the trunk (n=6). Patients in the atonic group fell straight downward, landed on their buttocks,
and recovered immediately. Analysis of the ictal EEGs showed that all attacks corresponded
to the generalized spike or polyspikes-and-wave complexes. In the atonic form, the
spike-and-wave morphology was characterized by a positive–negative-deep-positive wave
followed by a large negative slow wave. In two patients, the intensity of the atonia
appeared to correspond to the depth of the positive component of the spike-and-wave
complexes. We did not detect any significant differences in the clinical and EEG features
and prognosis, between the atonic and myoclonic groups.
Conclusions: Although the determination of exact seizure type is a prerequisite for
diagnosing an epileptic syndrome, the strict differentiation of seizure type into
either a myoclonic or atonic form, does not appear to have a significant impact on
the outcome or in delineating this unique epileptic syndrome. At present, we consider
it better to follow the current International Classification of Epileptic Syndromes
and Epilepsies until a more appropriate system than the clinico-electrical approach
for classifying patients with MAE is available.
Keywords
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Article info
Publication history
Accepted:
August 13,
2001
Received in revised form:
August 10,
2001
Received:
July 13,
2001
Identification
Copyright
© 2001 Elsevier Science B.V. Published by Elsevier Inc. All rights reserved.
