|Spinal stenosis is a narrowing of the spinal canal, the passageway in the spinal column, made of stacked vertebrae, through which the spinal cord and nerves pass. Spinal stenosis primarily occurs in the low back (lumbar spine) but may also occur in the middle back (thoracic spine) and the neck (cervical spine). |
Stenosis is classified as primary or secondary stenosis. Primary stenosis, which is also called congenital stenosis, is a developmental abnormality that results in narrowing of the canal. It is usually diagnosed in younger individuals who develop symptoms of stenosis. Secondary stenosis is a degenerative condition associated with changes in the spine that occur as part of the natural aging process. Changes may include bone spur or osteophyte formation, facet hypertrophy, bulging discs, and ligamentous hypertrophy. Secondary stenosis can also occur as a result of back surgery or trauma (acquired stenosis). Secondary stenosis is the most common type of spinal stenosis.
Individuals may also have a combined form in which primary stenosis is worsened by the development of secondary stenosis. The combined form occurs in individuals who are born with narrow spinal canals, which undergo further narrowing as a result of degenerative or postoperative changes.
In lumbar stenosis, narrowing of the spinal canal compresses the neural elements and reduces the blood supply to the nerves that supply sensation and motor control to the legs. Individuals most commonly present with complaints of fatigue or heaviness in their legs that occurs with walking and is relieved by sitting. In severe cases, even the nerves controlling bowel and bladder emptying may be affected. There are three places where the spinal nerves might be compressed, and the stenosis may be described by location: in the central canal of the spinal column (central stenosis), as the nerves leave the spinal column (foraminal stenosis), or just after the nerve has left the canal (lateral stenosis). Foraminal stenosis is the most common and typically affects the roots that comprise the sciatic nerve.
Risk: The average age of onset of symptoms of degenerative stenosis is 60 years, and men are afflicted twice as often as women. Primary or congenital stenosis may present by 30 years of age, and the risk of symptoms increases with age because of superimposed degenerative changes associated with aging. Individuals with osteoarthritis, rheumatoid arthritis, scoliosis, spondylolisthesis, achondroplastic dwarfism, and Paget's disease are at an increased risk of developing spinal stenosis.
Incidence and Prevalence: Five in 1,000 individuals over age 50, or about 250,000 to 500,000 individuals in the US, have symptoms of spinal stenosis (Hsaing). Because most individuals with mild spinal stenosis have no symptoms, the incidence can only be approximated. Symptoms do not occur until narrowing of the spinal canal has progressed enough to impinge on the nerve root(s) or the spinal cord. Seventy-five percent of spinal stenosis cases occur in the lumbar spine (Ray). Because the US population is aging, prevalence is expected to increase, growing by 18 million within the next decade (Hsaing).
Source: Medical Disability Advisor