Motor conduction measurement in myelopathy hand.

We studied the relationship between intramedullary high signal intensity (IMHSI) on T2-weighted magnetic resonance images and motor conduction in the spinal cords of cervical spondylotic myelopathy (CSM) patients. There was no significant difference between the biceps or triceps central motor conduction times (CMCTs) of the patients who did and did not exhibit IMHSI, whereas the abductor pollicis brevis CMCT was significantly longer in the patients who exhibited IMHSI (p<0.05) than in those who did not. The CMCT of the abductor pollicis brevis is sensitive to the degree of damage in the cervical spinal cord. Hand dysfunction is a characteristic of CSM regardless of the cervical level affected by the condition. The motor fibers innervating the intrinsic muscles of the hand in the long tract of the cervical spinal cord are more sensitive than other motor fibers. For this reason, we consider that myelopathy hand is a characteristic impairment of CSM. Transcranial magnetic stimulation of the hand motor cortex is useful for the evaluation of cervical myelopathy.