Clinical Investigation of the Lesions Responsible for Sensory Disturbance in Minamata Disease

Clinical Investigation of the Lesions Responsible for
Sensory Disturbance in Minamata Disease

MAKOTO UCHINO, SHUJI MITA, HIROSHI SATOH,³ TERUYUKI HIRANO, KIMIYOSHI ARIMURA,⁴
MASANORI NAKAGAWA,⁴ MASAAKI NAKAMURA, EIICHIRO UYAMA,YUKIO ANDO,¹
JUNJI WAKAMIYA⁵ and MAKOTO FUTATSUKA²

Department of Neurology, ¹Department of Laboratory Medicine, ²Department of Public Health, Kumamoto University School of Medicine, Kumamoto 860-0811,
³Neurology, Minamata City General Hospital and Medical Center, Minamata 867-0041,
⁴The Third Department of Internal Medicine, Kagoshima University Faculty of Medicine, Kagoshima 890-8520, and
⁵National Institute for Minamata Disease, Minamata 867-0008

To clarify the lesions responsible for sensory disturbance in Minamata disease (MD), we clinically investigated the characteristics of sensory disturbance. In all patients with the classical type MD, two-point discrimination was severely disturbed, but the involvement of superficial sensation was relatively mild. On short-latency somatosensory evoked potential study, the component corresponding to N20 was completely absent with normal N9, N11, and N13 components. Although 14 of 38 chronic MD patients demonstrated intact superficial sensation, 10 of these 14 showed mild to moderate disturbance in two-point discrimination. The two-point discrimination in chronic MD patients was significantly high irrespective of the disturbance of superficial sensation. These findings suggest that the sensory disturbance of MD patients may mainly be caused by a lesion in the sensory cortex rather than in the peripheral nerves. However, other foci could be also responsible for the sensory impairment, since 9 of 38 chronic MD patients showed intact two-point discrimination.

Keywords —— Minamata disease; sensory disturbance; two-point discrimination; classical type; chronic type

===============================

Tohoku J. Exp. Med., 2001, 195, 181-189

Address for reprints: Makoto Uchino, Department of Neurology, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto 860-0811, Japan.

e-mail: uchino96@kaiju.medic.kumamoto-u.ac.jp

This paper was presented at the 6th ICMGP (International Conference on Mercury as a Global Pollutant) in Minamata, Japan, October 15-19, 2001.