Spinal Stenosis

Low back pain is the third most common reason for physician visits among older adults. Spinal stenosis is one of several common causes of low back pain and is a common cause of back surgery in older adults. Degenerative spinal stenosis (narrowing) occurs when [Page 534]the structures of the spinal canal, or the openings where individual nerves exit the spine, narrow gradually with age. Such degenerative changes may include loss of intervertebral disc height and osteophyte (new bone) formation due to osteoarthritis, which can encroach on the central spinal canal and nerves. Bulging vertebral discs also may compress nerve structures. Spinal stenosis in older adults most commonly affects the lower lumbar spine. Resulting compression on these nerve structures causes pain and, in more severe cases, weakness.

Classically, patients complain of diffuse low back pain and pain in the legs exacerbated by standing or walking. Other activities that extend the spine, such as standing and lying prone, may also worsen symptoms. Positions that flex the spine, such as sitting and leaning forward while walking, may improve symptoms. Neurological abnormalities on physical examination may be lacking, but when they are present they may occur after a period of activity that evokes changes in reflexes, sensation, and increased pain. Other conditions that can cause similar back pain include peripheral arterial disease, in which leg pain occurs after a period of physical exertion (known as claudication), tumor, disc herniation, and mechanical back pain due to muscle strain.

Diagnosis is often made based on a description of pain and a physical examination. Radiographic studies are often reserved for those with more urgent symptoms or those not responding to a trial of conservative therapy. There may be a poor correlation between the severity of symptoms and the severity of X-ray changes. Most adults develop disc degeneration and arthritis of the spine, but not symptoms of spinal stenosis, as they age. In one study, up to 21% of older adults with stenotic changes on magnetic resonance imaging (MRI) were symptom-free. On the other hand, some patients have significant pain and functional disability despite minimal radiographic changes. For patients with atypical or continued pain or muscle weakness, or for those contemplating injections or surgical interventions, MRI is often done. A computed tomography (CT) scan with myelography may be used instead in selected circumstances.

Conservative management is frequently successful using anti-inflammatory or other analgesic medications to control pain and physical therapy to strengthen abdominal muscles. Walking, water therapy, and/or other exercise to maintain mobility is important. If these modalities do not bring relief over time, lumbar steroid injections may provide relief for many patients. Those who remain symptomatic may be candidates for surgical intervention to relieve pressure on the affected nerves. A majority of surgically treated patients reported good to excellent outcomes in one study. Ongoing work in this area continues to develop newer, less invasive decompressive procedures.