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The spinal canal, also called the vertebral canal or spinal cavity, is the space created by the vertebral column. The vertebral column is the tube-like structure comprised of many vertebra, which are ring-like bones, stacked on top of each other. These stacked rings, in turn, create a hollow kind of tube that houses and protects the soft nervous tissue of the spinal cord.
All vertebrates — animals with a spine — have a spinal canal. In humans, the canal is usually between 17 to 18 inches (43 and 45 cm) long, extending from the base of the brain down to the pelvis. It was first scientifically described, along with other parts of the central nervous system, by the 16th century French physiologist Jean François Fernel.
A common disease affecting this cavity is spinal canal stenosis, in which the canal narrows due to a thickening of bone and tissue. The thickening can occur for many reasons, including osteoporosis, tumors, or as a result of the natural effects of aging. Symptoms include a pinching sensation, pain, and numbness. When the narrowing occurs in the lower portion of the cavity, affecting the lower back and legs, it is called lumbar spinal canal stenosis.
This condition is often diagnosed with the aid of magnetic resonance imaging (MRI), and treatment can range from exercises to strengthen back muscles and support the spine, to more serious interventions, including drugs and surgery. Untreated, it can lead to injury of the spinal cord and neurological symptoms, including the loss of motor function.
Fractures or penetration of the spinal canal, whether from automobile accidents, bullet wounds, or other traumas, can damage the spinal cord and cause neurological symptoms that vary depending on the portion of the spinal cord affected and the severity of the trauma.
Deformities of the cavity and vertebrae include kyphosis, a harmful forward curvature of the spine, or scoliosis, a sideways curvature. Either condition, if severe enough, can affect the spinal cord and compromise the function of the nervous system. Sometimes, these conditions are congenital, though they may not become evident until a person's teenage years. Treatment can include braces to realign the vertebral column and surgeries.
Spina bifida is a frequently occurring birth defect. When vertebrae overlying the spinal cord do not properly form during the course of fetal development, babies can be born with a spinal cord that protrudes, unprotected, from an opening in the vertebrae. Pediatric neurosurgeons usually intervene shortly after birth, or even, in some cases, perform surgery on the developing fetus. The risk of spina bifida can be greatly reduced if the mother supplements her diet with folic acid prior to conception.