Studies of the etiology and pathogenesis of motor neuron diseases. III. Magnetic cortical stimulation in patients with lathyrism.

Neurophysiological assessments of central motor pathways were conducted of 11 Spanish subjects with varying degrees of spastic paraparesis (lathyrism). The disease has been induced more than 40 years ago by subsistance on the neurotixic chick pea Lathyrus sativus. Patient evolution was carried out by magnetic cortical and electric spinal stimulations and recordings of the contralateral muscle responses. Central motor conduction times corresponding to lower limbs were clearly more prolonged in those severely affected patients with marked difficulty walking (Stages 4 and 3). Central conduction times corresponding to upper limbs were delayed in only 1 patient. Taken together with clinical and published neuropathological data, these findings suggest that established lathyrism is essentially a central motor system disorder primarily affecting corticospinal tracts regulating the lower limbs.