Motor neuron disease on the Kii Peninsula of Japan: cycad exposure.

In the Hohara area of Nansei-cho, one of the foci of motor neuron disease (MND) on the Kii Peninsula, an inquiry was conducted to investigate whether cycad exposure is an etiological factor of MND in the western Pacific. Although cycads were commonly used as medicine around World War II all over Japan, the medicinal use of cycads was exceptional in the Hohara area. A questionnaire study in the Hohara and the neighboring four areas in Nansei-cho showed that cycad used as food, medicine, toys, and garden trees had no relation to the incidence of MND in these areas. The result in the Hohara area does not support the hypothesis that cycad is an etiological factor of MND common to the western Pacific foci.