Cervical spondylotic myelopathy

Cervical spondylotic myelopathy (CSM) is compression and injury of the spinal cord at the neck level, caused by degenerative changes in the cervical spine. It is the most common cause of spinal cord dysfunction in adults over 55 in developed countries.

**Anatomy and mechanism**

The spinal cord runs from the base of the brain down through the spinal canal — a protective bony tube formed by the vertebrae. It is surrounded by a few millimetres of cerebrospinal fluid that cushions it from normal movement.

With age, the cervical intervertebral discs lose height and may bulge; bone spurs (osteophytes) form on the vertebral endplates and facet joints; and the posterior longitudinal ligament and ligamentum flavum may thicken and buckle. These changes progressively narrow the spinal canal (*stenosis*), encroaching on the fluid-filled buffer around the cord. When the canal is narrow enough, the cord itself is compressed — disrupting the delicate nerve fibres that transmit motor and sensory signals to the arms, hands, and legs.

**Risk factors and natural history**

CSM is primarily a condition of ageing. It is more common in men and in individuals with a constitutionally narrow spinal canal. The rate of progression is unpredictable — some patients deteriorate rapidly, others experience prolonged periods of stability, and a minority improve spontaneously. Trauma (even minor) can precipitate acute worsening in patients with pre-existing stenosis.

**Diagnosis**

MRI is the investigation of choice, demonstrating cord compression and any signal change within the cord (indicating established injury). CT myelography is used when MRI is contraindicated. Neurophysiological studies (nerve conduction studies, somatosensory evoked potentials) can quantify functional deficit.

**Non-surgical management**

For mild or stable CSM without severe cord signal change: - Cervical collar to limit extreme flexion or extension - Physiotherapy: cervical stabilisation exercises, balance training, gait rehabilitation - Pain management: epidural steroid injections, pulsed radiofrequency for radicular pain, spinal cord stimulation for refractory pain - Close neurological monitoring — surgery is indicated if deterioration occurs

**Surgical decompression**

The primary goal of surgery is to relieve pressure on the spinal cord and prevent further neurological decline. Partial recovery of cord function is possible, particularly when surgery is performed before advanced cord damage has occurred, but the degree of recovery is difficult to predict.

Surgical approach depends on the level and pattern of compression, disc versus bony disease, cervical alignment, and other patient factors: - *Anterior approaches:* anterior cervical discectomy and fusion (ACDF); anterior cervical corpectomy and fusion — used when compression is primarily from the front (disc, osteophyte) - *Posterior approaches:* cervical laminectomy; laminectomy and fusion; laminoplasty — used for multilevel disease or predominantly posterior compression - *Combined anterior-posterior:* for severe multilevel disease or kyphotic deformity requiring realignment