Abstracts

Rationale: Benign adult familial myoclonus epilepsy (BAFME) is an autosomal dominant disease representing cortical tremor and infrequent generalized seizures. BAFME has been reported with various terminology from Japan and Europe. Despite many designations, apparently both Japanese and European patients have quite similar clinical phenotype and the findings of neurophysiological study disclosed the features of cortical reflex myoclonus such as giant somatosensory evoked potentials (SEPs), C-reflex and a preceding positive spike by jerk-locked back averaging (JLA). Although termed "benign", we reported that Japanese BAFME is currently considered possibly as a very mild form of progressive myoclonus epilepsy based on the clinical findings. However, the number of studied patients was not enough to clarify its clinical phenotype thoroughly since BAFME is a relatively rare syndrome. In the current study, we aimed to delineate the detailed epidemiological background of Japanese BAFME. Methods: After the previous survey (the first survey) about the current nationwide state of myoclonus epilepsy of adult in Japan, we conducted this second survey by means of the questionnaire. The questionnaires contained the patient demographic profiles, clinical features, electrophysiological examinations, neuroradiological examinations, and therapies. Diagnostic criteria for BAFME were defined and adopted basically from our previous report. This study protocol was approved by the institutional ethics committee at Kyoto University Hospital (E1148). Results: Based on the clinical diagnostic criteria, we analyzed demographic and clinical characteristics of the 101 BAFME patients in 74 families. BAFME patients were slightly female predominant and were widely distributed throughout Japan. Ninety-two patients (92/101, 91.1%) showed cortical tremor and 84 (84/101, 83.2%) showed epileptic seizures. Although the epileptic seizures in BAFME patients have been considered to be infrequent, 22.6% of patients had more than one seizure per year at the fastigium. Three patients (3/101, 3.0%) showed cerebellar ataxia, 8 (8/101, 7.9%) cognitive impairment and 13 (13/101, 12.9%) psychiatric symptoms. The main findings of a brain MRI were normal in 74% and the remaining patients showed nonspecific abnormal findings. Sodium valproate and clonazepam were the main agents for BAFME patients. The older patients showed a significantly severer degree of and higher rates of abnormal electrophysiological examinations suggestive of cortical hyperexcitability than the younger patients, which was seen especially in the C-reflex (p < 0.05). Conclusions: Our study successfully delineated the overall clinical characteristics of Japanese BAFME. Based on this survey, we can propose clinical and electrophysiological diagnostic criteria for Japanese BAFME. The genetico-clinico-electrophysiological correlates will be very important to seek for the definite causative gene for Japanese BAFME. Funding: The Research Grant (22A-6) for Nervous and Mental Disorders from the Ministry of Health and Welfare and the Grants-in-Aid for Scientific Research (23591275) from the Japan Society for the Promotion of Science (JSPS).