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.