Spinal stenosis is the narrowing of nerve passages in the spine. It occurs when the bones, ligaments or discs of the spine squash the nerves of the spine (usually the sciatic nerve) causing pain, usually in the lower back and legs. It usually affects people in late middle age and older.
- age-related changes in the spine
- changes in the ligaments of the spine
- diseases of the bone, such as Paget’s disease
Less commonly, sciatica may be caused by:
- a growth within the spine, such as a tumour
The space within the spinal canal may narrow without producing any symptoms. However, if narrowing places pressure on the spinal cord, cauda equina, or nerve roots, there may be a slow onset and progression of symptoms. The neck or back may or may not hurt. More often, people experience numbness, weakness, cramping, or general pain in the arms or legs. If the narrowed space within the spine is pushing on a nerve root, people may feel pain radiating down the leg (sciatica). Sitting or flexing the lower back should relieve symptoms. (The flexed position “opens up” the spinal column, enlarging the spaces between vertebrae at the back of the spine.) Flexing exercises are often advised, along with stretching and strengthening exercises.
People with more severe stenosis may have problems with bowel and bladder function and foot disorders. For example, cauda equina syndrome is a severe, and very rare, form of spinal stenosis. It occurs because of compression of the cauda equina, and symptoms may include loss of control of the bowel, bladder, or sexual function and/or pain, weakness, or loss of feeling in one or both legs. Cauda equina syndrome is a serious condition requiring urgent medical attention.
In many cases, the conditions causing spinal stenosis cannot be permanently altered by nonsurgical treatment, even though these measures may relieve pain for a period of time. To determine how much nonsurgical treatment will help, a doctor may recommend such treatment first. However, surgery might be considered immediately if a patient has numbness or weakness that interferes with walking, impaired bowel or bladder function, or other neurological involvement. The effectiveness of nonsurgical treatments, the extent of the patient’s pain, and the patient’s preferences may all factor into whether or not to have surgery.
The purpose of surgery is to relieve pressure on the spinal cord or nerves and restore and maintain alignment and strength of the spine. This can be done by removing, trimming, or adjusting diseased parts that are causing the pressure or loss of alignment. The most common surgery is called decompressive laminectomy: removal of the lamina (roof) of one or more vertebrae to create more space for the nerves. A surgeon may perform a laminectomy with or without fusing vertebrae or removing part of a disk. Various devices may be used to enhance fusion and strengthen unstable segments of the spine following decompression surgery.
Patients with spinal stenosis caused by spinal trauma or achondroplasia may need surgery at a young age. When surgery is required in patients with achondroplasia, laminectomy (removal of the roof) without fusion is usually sufficient.