 Cervical spondylotic myelopathy CSM is a syndrome consisting of symptoms and signs of cervical spinal cord compression caused by chronic degenerative changes of the cervical spine. CSM is the most serious and disabling condition of cervical spondylosis. Natural history studies showed that most of the CSM patients have a progressive deterioration course and no spontaneous regression occurs. It is suggested that the patients with moderate to severe CSM should be operated as early as possible before neurological deficits are too pronounced. 