Epilepsy with myoclonic absences is a syndrome in which patients have rhythmic myoclonic jerks of the shoulders, arms, and legs with a concomitant tonic contraction. Perioral myoclonias are frequent but eyelid twitching is unusual. The tonic component mainly affects shoulder and deltoid muscles that may cause elevation of the arms. The duration of the absences varies from 8 to 60 seconds.
Myoclonic absences typically occur multiple times daily and often are very difficult to treat.65 The EEG typically shows generalized, rhythmic 3 Hz spike-wave or polyspike-wave.
The myoclonic jerks in this syndrome are quite prominent. More subtle myoclonus often occurs as a component of absence seizures. In a study of 426 typical and 500 atypical absence seizures in 54 children in which simultaneous EEG frequency modulation radiotelemetry and videotape monitoring were deployed, Holmes and colleagues66 found myoclonic jerks in 13% of typical absences and 12% of atypical absences.
In this study, absence seizures were classified by EEG criteria. Seizures with generalized, regular, symmetric spike-and-wave discharges were classified as typical absences. Absences with slow (<2.5 Hz), irregular, or asymmetric spike-and-wave discharges were classified as atypical absences.
Reviewed and revised January 2004 by Gregory L. Holmes, MD, Dartmouth Medical School
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