Central motor conduction in motor neuron disease.

Central motor conduction time (CMCT) to abductor digiti minimi (ADM) and tibialis anterior (TA) was measured in 21 patients of motor neuron disease (MND). In the upper limb, the motor pathways were inexcitable in 13 and central motor conduction time (CMCT-ADM) was prolonged in 7 sides. In the lower limbs the motor pathways were inexcitable in 10 and CMCT-TA was prolonged in 14 sides. The CMCT abnormalities did not follow a constant pattern but were randomly distributed and were asymmetric in the upper limbs in 7 and lower limbs in 3 patients. Asymmetric and randomly focal abnormalities in central motor conduction in our patients are consistent with asymmetric and focal neuronopathy in MND.