[A case of familial essential myoclonus--electrophysiological study].

A case of familial essential myoclonus was reported with electrophysiological studies. A 58-year-old female presented with involuntary movement (myoclonic jerk) since age 6 years. At the age over 50, she developed difficulty in writing and fine finger movements. Two years ago, the diagnosis of hyperthyroidism was made, but she did not take any anti-thyroid medication. She was admitted to our hospital for further evaluation of myoclonus. On family history, her grandson (4-years-old) had myoclonus. On general physical examination, she showed a diffuse goiter. On neurological examination, she showed spontaneous myoclonus in the face, neck, trunk and the proximal limb muscles, especially in the left upper and right lower extremities. The myoclonus was exacerbated with auditory stimulation and emotional tension, but there was no temporal relationship between each stimulus and myoclonus. There was no myoclonus during sleep. Finger-to-nose test showed coarse intention myoclonus. Laboratory examinations including lysosomal enzyme assay revealed no abnormalities except for the decrease in total cholesterol (118 mg/dl) and the increase in serum lactate (19.7 mg/dl). The serum concentration of thyroxin was 18.4 micrograms/dl, that of triiodothyronine 3.0 ng/ml, and that of thyroid stimulating hormone (TSH) 0.027 microIU/ml. Anti-thyroglobulin antibody and anti-microsomal antibody were positive (X100, X6400). Neurological laboratory tests were normal including cerebrospinal fluid, peripheral nerve conduction study, electromyogram (EMG), muscle biopsy, cranial computed tomography and magnetic resonance imaging, and positron emission tomography. Electron transport system of the biopsied muscle was normal. So, we made a diagnosis of familial essential myoclonus and hyperthyroidism. In the electrophysiological studies, the electroencephalogram (EEG) was within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)