Familial cortical tremor, epilepsy, and mental retardation: a distinct clinical entity?

OBJECTIVE To describe a European family with cortical tremor, epilepsy, and mental retardation, the pedigree of which indicates an autosomal dominant inheritance of the disease. DESIGN Clinical, laboratory, neurophysiological, and neuroimaging data were studied. SETTING Institute for research on mental retardation. PATIENTS Two siblings (aged 25 and 28 years) and their 49-year-old mother had postural and action tremor, seizures, and mental retardation. Only tremor was present in the maternal grandmother (aged 68 years). The electroencephalogram showed diffuse spike-and-wave complexes and/or posterior spikes, and a photoparoxysmal response in the 4 subjects. The typical electrophysiologic features of cortical reflex myoclonus, such as giant somatosensory evoked potentials, enhancement of the C-reflex, and jerk-locked premyoclonus spikes, were found in all patients. CONCLUSION This syndrome may represent a specific form of familial cortical tremor with a benign form of epilepsy and a new genetic model of cortical hyperexcitability inherited with an autosomal dominant mechanism.