[Central motor conduction time in the pseudopolyneuritic form of amyotrophic lateral sclerosis]

Central motor conduction time (CMCT) from the cerebral motor cortex to the cervical segment of the spinal cord (C-CMCT) and CMCT from the cortex to the lumbar segment of the spinal cord (L-CMCT) were estimated using percutaneous electrical cortical, cervical and lumbar stimulation in 8 patients with pseudopolyneuritic form of amyotrophic lateral sclerosis (ALS). The results were compared to those in 18 patients with bulbar and common forms of ALS and 13 normal control subjects. Both the C-CMCT and the L-CMCT were remarkably prolonged in pseudopolyneuritic form of ALS as well as in bulbar and common forms of ALS. These results were consistent with the morphological findings that the large myelinated fibres in the corticospinal tract are depleted in pseudopolyneuritic form of ALS in which deep tendon reflexes are hypoactive and pyramidal sings are not obvious. The evaluation of CMCT is suggested to be useful for diagnosis of ALS in which upper motor neurone disorder is not manifested.