Abstracts

Rationale: A proband with progressive myoclonus epilepsy was identified and had a strong family history of epilepsy. The spectrum of myoclonic epilepsies in his wider family was delineated.Methods: Family members underwent electroclinical phenotyping using a validated seizure questionnaire. Previous medical history and investigations were obtained including EEGs, video-EEG monitoring and MRI.Results: This New Zealand family of European ancestry had a pattern of autosomal dominant inheritance of seizures affecting 7 individuals over 2 generations. Seizures began at a mean of 14.5 years (range 12 17 years) in normal individuals. 6/7 individuals had sporadic myoclonic seizures; 5 also had photic-induced myoclonus and 4 had photic-induced occipital seizures. Two females had convulsive seizures which were generalized in onset whereas 4 individuals had convulsive seizures of focal onset. EEG studies showed generalised spike wave and polyspike wave induced by photic stimulation and pattern stimulation at onset in 4/6 individuals. Two individuals also had occipital spikes on photic stimulation. MRI scans were normal in the 4 affected individuals tested. Extensive metabolic investigation was normal in the proband. Two individuals had Juvenile Myoclonic Epilepsy (JME). Four individuals with photically induced occipital seizures and myoclonic seizures presented with a JME/idiopathic photosensitive epilepsy (IPOE) overlap. The females had mild epilepsy which did not require treatment or was easily controlled. The males were more severely affected with early intractability and subsequent tremor, anxiety and periods of frequent seizures and/or status epilepticus. The proband and his uncle had Myoclonic Occipital Photosensitive Epilepsy with Dystonia (MOPED): a progressive myoclonus epilepsy with deterioration in their early 30s. They developed episodes of paroxysmal cervical dystonia with cognitive decline during periods of poor seizure control. One stabilized after years of poor seizure control but had intractable epilepsy with periods of deterioration. The other deteriorated with episodes of status dystonicus and status epilepticus, ataxia and a progressive opthamoplegia before he died at 38 years. The family has been mapped and multiple linkage peaks identified; sequencing of candidate genes is underway. Conclusions: This autosomal dominant family presents with a novel familial syndrome in which mildly affected individuals have JME or JME/IPOE overlap. Severely affected individuals have a progressive photosensitive myoclonus epilepsy with paroxysmal dystonia. Molecular studies on this family will lead to a gene for myoclonus and photosensitivity.