Centre Saint-Paul, 300, boulevard de Sainte-Marguerite, 13258 Marseille 09, France.
A 21-year old man with marked developmental delay was referred for the diagnosis of myoclonic jerks (MJ), which were sometimes responsible for sudden falls without loss of consciousness, that had begun 2 years before, and for a recent generalized tonic-clonic seizure preceded by a cluster of MJ. Physical examination revealed a small stature, bilateral pyramidal signs, severe mental retardation, and retinis pigmentosa. Etiological factors for this encephalopathy were not found (muscle and skin biopsies, karyotype and extensive blood chemistry). Waking interictal EEG showed a normal background activity and generalized poly-spike-and wave (PSW) discharges. Photic stimulation disclosed a marked photoparoxysmal response, sometimes associated with myoclonic jerks. Three spontaneous jerks accompanied by a burst of generalized PSW were recorded on awakening from a nap. The MRI disclosed wide ventricles, a thin corpus callosum, brainstem atrophy and a so-called “redundant gyration”; these changes were evocative of acquired perinatal damage. Juvenile myoclonic epilepsy (JME) was diagnosed and valproate was started resulting in complete control of seizures. During a 5-year follow-up, the patient has remained seizure-free and the EEG consistently normal. In our opinion, JME can be diagnosed in very uncommon settings, including patients with significant brain damage, as long as all the other criteria for the diagnosis are present.