The patient was a 64-year-old woman who showed muscle weakness and tremor of upper extremities and gait disturbance at the age of 62 years. The symptoms progressed and she was admitted to our hospital. Neurological examination revealed muscle weakness, muscle atrophy and fasciculation bilaterally in the upper extremities. The deep tendon reflexes were reduced in the upper extremities and increased in the lower extremities, but Babinski's sign was not present. There was mild hand tremor at rest (right greater than left). Muscle rigidity was also evident. Her gait was small-stepped and her trunk was bent forward. She showed hypomimia, but no dementia was detected. She died of respiratory failure 7 months after admission. The duration of the illness was about 2 years. At autopsy, macroscopic examination showed depigmentation of the substantia nigra and locus ceruleus, and atrophy of the anterior roots of the spinal cord. Microscopic examination revealed a few senile plaques in the temporal cortex. In the substantia nigra, the number of melanin-containing cells was decreased in its central parts. A few Lewy bodies were found in some of the remaining neurons, and melanin pigment migrated into the parenchyma. In the locus ceruleus and dorsal motor nucleus of vagus, abundant Lewy bodies and mild astrocytosis were seen. A few Lewy bodies were also seen in the nucleus raphe, nucleus basalis of Meynert and hypothalamic nuclei. Severe neuronal loss of the anterior horn cells was observed in the cervical segment, and to a lesser degree, in the lumbo-sacral segments. segments.(ABSTRACT TRUNCATED AT 250 WORDS)