Degenerative spondylotic myelopathy (DSM)

Definition

Degenerative spondylotic myelopathy (DSM), or as it is also called, discogenic myelopathy, is a dystrophic disease of the spinal cord due to its compression and ischemia as a result of compression by a herniated disc. Discogenic myelopathy, depending on the level of lesion, is manifested by spastic and flaccid paresis, sensory disturbances, and pelvic disorders. Diagnosis of myelopathy caused by disc herniation includes neurological examination, radiologic and tomographic studies of the spine, electromyography, and, if necessary, study of cerebrospinal fluid. Discogenic myelopathy is subject to surgical treatment (laminectomy, discectomy, microdiscectomy), followed by rehabilitation treatment (medications, physiotherapy, massage, reflexology).

General information

Degenerative-dystrophic lesions of the spinal cord (myelopathies) may have different genesis: vertebrogenic, dysmetabolic, traumatic, atherosclerotic, tumor. The most common in clinical neurology and vertebrology is vertebrogenic myelopathy, specifically discogenic myelopathy. As the name suggests, discogenic myelopathy is closely related to intervertebral disc pathology. In most cases, it is a severe complication of osteochondrosis of the spine. As a rule, such discogenic myelopathy is observed in people aged 45-60 years, more often in men. It is characterized by the gradual development and worsening of symptoms, capturing a period of several months to several years. In rarer cases, discogenic myelopathy is a consequence of spinal trauma. In this case, it has an acute course and is considered part of post-traumatic myelopathy.

Causes of discogenic myelopathy

Degenerative changes in the intervertebral disc, which are accompanied by osteochondrosis of the spine, lead to stretching and tearing of the disc’s fibrous ring and its peripheral fibers from the vertebral bodies. It leads to displacement of the intervertebral disc with the formation of an intervertebral hernia. If the displacement is not accompanied by a rupture of the fibrous ring, it is labeled as a “disc protrusion.” If the fibrous ring is ruptured and the pulposus nucleus of the disc comes out, it is referred to as “disc extrusion.” Most often, the displacement of the intervertebral disc occurs in the posterior-lateral direction, just where the spinal cord and the blood vessels supplying it pass.

Discogenic myelopathy develops not only due to direct compression of the spinal cord by a part of the disc that has protruded from the intervertebral space. Spinal cord ischemia in discogenic myelopathy is characterized by gradual development and a chronic character. Secondary adhesions after spinal surgery or trauma can cause discogenic myelopathy. Osteophytes formed during osteochondrosis can aggravate the situation, additionally compressing the spinal cord, its roots, and vessels.

Reduced spinal blood circulation due to compression of spinal vessels and direct compression of the spinal cord leads to hypoxia and disturbances in the tropism of brain cells. As a result, nerve cell death occurs in the affected area, causing the main clinical manifestations of discogenic myelopathy.

Classification of discogenic myelopathy

Discogenic myelopathy is classified depending on the spine section in which pathological changes develop. The most common is cervical discogenic myelopathy, followed by lumbar discogenic myelopathy. Such pathology is observed in rare cases in the thoracic spine, where it is localized mainly in the lower thoracic segments.

Symptoms of discogenic myelopathy

The basis of the clinical picture of discogenic myelopathy is a gradually increasing neurological deficit of the motor and sensory spheres. Motor disorders of discogenic myelopathy are manifested by decreased muscle strength (paresis), accompanied by muscle tone disorders and changes in tendon reflexes. Below the level of myelopathic changes, they have a central (spastic) character and, at the level of the affected segments of the spinal cord – a peripheral character. Sensory disorders are expressed in a decrease in superficial and deep sensitivity and the appearance of paresthesias. Typical for discogenic myelopathy is the predominance of motor disorders over sensory disorders. At the beginning of its development, myelopathy may manifest itself as unilateral disorders corresponding to the side of the spinal cord lesion. Over time, there is a “transition” of symptoms to the second side. Urinary disorders are possible. Often, discogenic myelopathy is accompanied by sciatica. However, radicular pain is usually expressed moderately and is secondary to motor disorders.

Cervical discogenic myelopathy is manifested by peripheral paresis in the hands and spastic paresis in the legs. There are paresthesias in the hands, slight superficial hypoesthesia and inconstant decrease in deep sensitivity in the hands, decrease or loss of all types of sensitivity in the trunk and legs. Muscle atrophy in the proximal arms is characteristic. Cervical discogenic myelopathy can develop in combination with vertebral artery syndrome. In such cases, along with symptoms of myelopathy, there are signs of dyscirculatory encephalopathy in the vertebrobasilar basin: dizziness, memory loss, vestibular ataxia, noise in the head, sleep disorders, etc.

Lumbar discogenic myelopathy is characterized by peripheral leg paresis accompanied by muscle atrophy, reduced or absent knee and Achilles reflexes, urinary retention, and sensory ataxia. Intermittent claudication syndrome may be observed, requiring differential diagnosis with obliterative atherosclerosis and obliterative endarteritis of the lower limb vessels.

Diagnosis of discogenic myelopathy

A detailed neurological examination helps the neurologist to identify signs of spinal cord damage and determine the level of its localization. For a more accurate diagnosis of the causes of the development of myelopathy, it is necessary to consult an orthopedist or vertebrologist. Radiography of the spine in discogenic myelopathy determines the narrowing of intervertebral gaps characteristic of osteochondrosis, the appearance of osteophytic growths along the edges of the vertebrae. To determine the level and degree of compression of the spinal cord, patients with discogenic myelopathy undergo myelography. MRI of the spine and CT of the spine are used to visualize disc herniation and exclude other causes of myelopathy.

Electroneurography and electromyography are also used to diagnose discogenic myelopathy. If it is necessary to assess the blood circulation of the affected spine area, angiography is resorted to. Cervical discogenic myelopathy with signs of circulatory insufficiency in the vertebrobasilar basin is an indication for rheoencephalography and ultrasound of the head and neck vessels.

Discogenic myelopathy requires differentiation from spinal cord tumors, vascular myelopathy, amyotrophic lateral sclerosis, spinal diseases of inflammatory genesis (myelitis), multiple sclerosis, and funicular myelosis. A lumbar puncture may be performed as part of the differential diagnosis of discogenic myelopathy. In discogenic myelopathy in cerebrospinal fluid, no significant changes characteristic of other spinal cord diseases are noted. There may be some increase in protein content, but it does not reach the same degree as in spinal tumors.

Treatment of discogenic myelopathy

Spinal cord compression with the development of discogenic myelopathy is an indication for surgical treatment. Conservative treatments such as dry and underwater spinal traction can be used in the treatment of herniated discs that are not complicated by myelopathy.

The most common surgery for discogenic myelopathy is decompression of the spinal canal by laminectomy. If necessary, it can be supplemented with facetectomy. In the lumbar region, puncture decompression of the disc may be used. More radical treatment options, mainly used for large herniated discs, include discectomy and microdiscectomy.

In the postoperative period, complex rehabilitation treatment is necessary, aimed at maximizing the restoration of motor functions lost due to discogenic myelopathy. It includes drug therapy (chondroprotective, B vitamins, anticholinesterase, and vascular drugs), massage (classical and myofascial), electrical stimulation, and various types of reflex therapy.

All these treatment options are available in more than 770 hospitals worldwide (https://doctor.global/results/diseases/degenerative-spondylotic-myelopathy-sm). For example, Laminoplasty can be done in 31 clinics across Turkey for an approximate price of $8.1 K (https://doctor.global/results/asia/turkey/all-cities/all-specializations/procedures/laminoplasty). 

Prognosis and prevention of discogenic myelopathy

Compression of the spinal cord leads to the death of its neurons, which causes the appearance of persistent neurological deficits in the motor and sensory spheres. Only in the initial stage of discogenic myelopathy can surgical treatment and subsequent rehabilitation restore motor function. Surgery performed later stops the progression of myelopathy symptoms, but the neurological disorders formed are, as a rule, irreversible and lead to the patient’s disability.

Prevention of discogenic myelopathy is reduced to the prevention and timely treatment of spinal osteochondrosis and herniated discs.