Spinal Stenosis: Types, Causes, Risk Factors, Signs, Symptoms, Treatment
Spinal stenosis is abnormally narrowed spinal canal that may occur anywhere in spine causing restriction and pressure to spinal cord and nerves originating from spinal cord resulting in neurological deficits.1 Spinal cord gets narrowed at vertebral canal, which is a foramen between vertebrae where spinal cord passes through. Spinal stenosis is usually caused by wear and tear changes in the spine due to aging. In some people, spinal stenosis may not cause any symptoms; in others symptoms commonly present are pain, numbness, paresthesia and loss of motor control. Spinal stenosis is of three types: Lumbar stenosis, cervical stenosis and thoracic spinal stenosis.2 Lumbar spinal stenosis is by far most common, but cervical spinal stenosis is potentially serious condition, since it involves compression of spinal cord. Very rarely is thoracic spinal stenosis developed. Surgery is recommended in severe cases of spinal stenosis to create additional space for the spinal cord or the nerves.
Classification and Types of Spinal Stenosis
- Lumbar Spinal Stenosis: This is generally caused due to degenerative arthritis. In this type, nerve roots in lower back get compressed resulting in symptoms of sciatica like tingling, weakness, numbness radiating from lower back to buttocks, especially with activities. Surgery is generally recommended when conservative treatments are ineffective and the person continues to have increasing weakness of legs or bowel and bladder dysfunction. Surgery consists of lumbar decompression along with, or even without, fusion. Surgery is generally extremely beneficial for relieving leg symptoms, but it is not so beneficial for back pain.
- Cervical Spinal Stenosis: It is narrowing of spinal canal in neck. Spinal nerves facilitate feeling, moving and controlling bowel and bladder function along with other functions in body. In this condition, spinal canal gets narrowed resulting in compression of nerve roots where they exit from spinal cord. Sometimes, it irritates or injures spinal cord itself. Cervical spine has seven vertebrae present between head and chest. Compression of nerves and cord in cervical spine causes stiffness, pain, and numbness in neck, upper and lower extremities.3 It is a potentially serious condition since it compresses spinal cord which may in turn lead to other serious conditions like paralysis. It is a bone disease causing spinal canal narrowing at level of neck usually due to degeneration but it also sometimes is congenital. First line of treatment for this condition is surgery.
- Thoracic Spinal Stenosis: Spinal stenosis or narrowing of the spinal canal in the middle back region is known as thoracic spinal stenosis. This involves any of the thoracic vertebrae from T1-T12. As the thoracic vertebrae are joined to the ribs, thoracic spinal stenosis' clinical picture is different than spinal stenosis in other areas of the back and because of this unique interconnectivity of the thoracic vertebrae and the ribs, the primary motion affected by thoracic spinal stenosis is the body's ability to rotate, twist or move from side to side. Symptoms of thoracic spinal stenosis are: Pain in the affected area of the back, in the ribs with radiation down the back or legs, pain in the legs causing difficulty in walking and pain in one or more internal organs. Spinal stenosis in the thoracic region may be congenital, but in most cases it is a result of the natural aging process. Wear-and-tear, injury or overuse of the thoracic vertebrae and the other vertebrae leads to multiple medical conditions such as degenerative disc disease, herniated disc, bulging disc and bone spurs.
Pathophysiology of Spinal Stenosis
Spinal stenosis is usually caused due to degenerative disease of the spine leading to reduced diameter of the spinal canal and narrowing of the lateral recess and neural foramina.4 Spinal stenosis may also be due to hypertrophy of the bones and ligaments, intervertebral disc protrusion and spondylolisthesis. Compression of the cauda equina and the exiting nerve roots cause the leg symptoms. Symptoms of claudication are caused due to the reduction of the sagittal diameter of the central canal and leading to compression of the exiting nerve roots. Radicular symptoms are due to narrowing of the lateral recess and neural foramina. Disc degeneration changes the mechanics of the intervertebral disc and the facet joints. As the disc loses water and the ability to withstand burden, greater load is placed on the facet joints causing arthritic changes leading to synovitis, articular cartilage degeneration and articular surface enlargement.
Degeneration of the facet joints further causes stress on the discs, internal disc disruption and development of osteophytes. Degenerative changes can be seen on x-ray, CT scan or MRI. Mechanical compression and inadequate blood flow and oxygenation of the nerve roots or cauda equina may cause radiculopathy and neurogenic claudication. Standing and walking transiently enhances lordosis, leading to increase in stenosis and symptoms. Whereas forward flexion and sitting opens the canal, improves blood flow and relieves symptoms. Degenerative change of the spine is a part of ageing. These changes start when people are in their 20s. Lumbar stenosis causes degeneration of the posterior elements leading to anterior slippage of the superior vertebral body resulting in spondylolisthesis. This occurs commonly at the L4-L5 level and increases the underlying spinal canal stenosis. These degenerative changes within the disc and facets produce low back pain. Symptomatic lumbar stenosis is most common at L4-L5, then L3-L4, L2-L3 and least at L5-S1.
Causes and Risk Factors of Spinal Stenosis
- Aging factors causing ligaments to thicken, development of bone spurs, disc bulging and herniation, break down of facet joints, compression fractures of the spine commonly occurring in osteoporosis.
- Osteoarthritis and rheumatoid arthritis.
- Congenital causes like spinal canal being too small at birth.
- Hereditary factors like structural deformities of the vertebrae causing narrowing of the spinal canal.
- Bone diseases like Paget's disease and achondroplasia.
- Tumors of the spine.
- Trauma, injury or accidents may cause dislocation of the spine and the spinal canal and burst fractures.
Signs and Symptoms of Spinal Stenosis
- Discomfort with standing
- Lower extremity pain along with weakness and numbness
- Impinged nerve
- Intermittent claudication
- Bladder and/or bowel dysfunction
- Nocturnal pains
- Ambulatory disturbance
- Structural deformity
- Unintentional loss of weight
- Previous tumors
- Severe pain with lying down
- Recent injury with fractures
- Neurologic deficits
- Low back pains
- Cauda equina syndrome.
Treatment for Spinal Stenosis
- The following medications can be used: NSAIDs such as ibuprofen and naproxen help in reducing pain and inflammation. Muscle relaxants such as cyclobenzaprine help in relaxing muscle spasms that may occur with spinal stenosis. Antidepressants such as amitriptyline help in chronic pain. Anti-seizure drugs such as gabapentin (Neurontin, Gralise) and pregabalin (Lyrica) help in reducing the pain caused by damaged nerves. Opioids like oxycodone (Oxycontin, Percocet, others) and hydrocodone (Lortab, Vicodin, others) may also be used, but can be addictive.
- Physical Therapy (PT) may help in strength and endurance building, maintaining the flexibility and stability of the spine and improving balance.
- Steroid Injections around the area of stenosis may help in reducing the inflammation and relieve pressure. However, frequent steroid injections may weaken the surrounding bones and connective tissue; hence they should be used with caution.
- Surgery is considered if conservative treatments have failed and symptoms are interfering with daily activities of living. A laminectomy removes the posterior part of the affected vertebra and creates more space within the spinal canal. In some cases, vertebrae may need to be fused together to preserve spinal strength. Usually surgery helps in reducing the spinal stenosis symptoms, but in some patients symptoms remain the same or worsen after surgery. Surgical risks comprise of infection, tear in the membrane covering the spinal cord, blood clot in lower extremity veins and neurological deterioration.
Investigations for Spinal Stenosis
- Medical history and physical examination
- CT scan
- CT myelogram.