Cervical flexion myelopathy is thought to arise following compression of the spinal cord by vertebrae or intervertebral discs and dura mater, or from overstretching of the spinal cord induced by cervical spinal flexion. However, the influence of spinal flexion on the spinal cord and the detailed origins of this disease are unknown. In this article the authors report a case of cervical flexion myelopathy in which dynamic electrophysiological examination was performed using an epidural electrode. This investigation showed the real-time influence of flexion of the cervical spine on spinal cord function. This technique was considered to be useful for diagnosis and in decision making for treatment. Anterior fusion was the optimal surgical method for treating this disease.