Central motor conduction time in patients with HTLV-1 associated myelopathy

Transcranial electrical stimulation of the motor cortex was performed in 7 patients with human T-lymphotropic virus type-I associated myelopathy (HAM) and 15 normal subjects. The mean value of central motor conduction time (CCT) for the thenar and hypothenar muscles in patients with HAM was not different from that in normal subjects. In contrast, mean CCT value for the tibialis anterior and gastrocnemius muscles in patients with HAM was 8.54-10.34 ms longer than the value in normal subjects. These findings indicate that the lesion of pyramidal tract involvement in patients with HAM is mainly localized in the descending corticomotoneuron pathways at the thoracic spinal cord level. This technique could be used in a clinical study without untoward side effects, and may be valuable in detecting clinically silent lesions involving the pyramidal tract.