Minamata disease (organic mercury poisoning): neuroradiologic and electrophysiologic studies.

We studied 10 patients with Minamata disease (organic mercury poisoning) who have been followed for over 20 years. CT revealed a bilateral, symmetric, low-density area in the visual cortex and diffuse atrophy of the cerebellar hemispheres and vermis, especially the inferior vermis. Computerized quantitative analysis of the tremor of these patients showed a peculiar frequency of 7.075 Hz on postural tremor and 7.501 Hz on action tremor. On studies of short-latency somatosensory evoked potential, all patients showed a lack of the N20 component, the potential of the somatic sensory area.

Chronic sensory and autonomic neuropathy.

A man with sensory neuropathy had evidence of autonomic failure: abnormal pupils, hypohidrosis, esophageal dilation, diarrhea, hypotension, orthostatic hypotension, sphincter disturbance, and impotence. Functional tests revealed abnormalities of both sympathetic and parasympathetic systems, mainly postganglionic. Autopsy revealed degeneration of posterior columns, posterior nerve roots, posterior root ganglia, and peripheral nerves. Degeneration was also observed in the sympathetic trunk, vagal nerve, and myenteric plexus. Neurons in the intermediolateral columns were preserved. Progressive sensory neuropathy with dysautonomia seems to be a new disease.