Spinal stenosis is a narrowing or stricture of the lower part of the spinal canal that results in neurogenic claudication. Symptoms begin with progressive degenerative changes and compression, although the severity is not necessarily associated with the degree of compression seen on imaging studies. The etiology can be congenital or acquired. Congenital stenosis typically causes symptoms earlier in life. Acquired stenosis is usually a result of degenerative disease but can also be caused by back surgery, disorders such as Paget's disease or ankylosing spondylitis, or trauma. Garfin and associates reviewed the pathophysiology and surgical management of spinal stenosis.
Biomechanical and biochemical changes lead to decreased disc height with annular bulging, disc herniation and early osteophyte formation. The foraminal space narrows, resulting in nerve entrapment. A gradual shift in spinal alignment (kyphosis or lordosis) exacerbates the stenosis, exerting additional pressure on the neural elements. Decreased rotational accommodation coupled with altered motion cause inflammation of the cauda equina and, ultimately, pain. Compression combined with inflammation and irritation of the nerve root causes symptoms in the lower extremities. Decreased blood flow can be another factor related to symptoms.
Early symptoms are often insidious in onset, with vague complaints of lower back pain and stiffness. Symptoms are exacerbated by activity and relieved by rest. The classic symptoms of spinal stenosis, or acute neurogenic claudication, involve the lower extremities and include pain, numbness and tingling in the posterior or posterolateral aspect of the extremity. Patients may report that the pain or numbness starts distally and progresses proximally. Symptoms can be asymmetric or vary from side to side. A sudden onset of pain in the lower extremities or a worsening of pre-existing pain may signal concomitant disc herniation or a more acute decrease in vascular supply. Pain is usually exacerbated with spinal extension and decreased with flexion. Urinary dysfunction is uncommon, but many patients report a feeling of urgency.
Results of general physical and neurologic examinations are frequently normal, although asymmetric knee or ankle reflexes are possible, as well as muscle weakness in the lower extremities. However, a specific motor deficit is uncommon. Results of a straight-leg raising test are characteristically negative. Anteroposterior and lateral flexion-extension radiographs provide additional information in evaluations for degenerative spondylolisthesis or other evidence of movement dysfunction. Computed tomography without contrast material does not visualize neural elements well and is not recommended. Magnetic resonance imaging (MRI) should be reserved for surgical planning because the diagnosis can be made on the basis of the history, physical examination and radiographs.
Nonoperative treatment includes education, reassurance, analgesics, nonsteroidal anti-inflammatory drugs and narcotics, if necessary. Aerobic conditioning is useful, and intermittent use of a corset-type brace can be of limited use. Epidural injection of steroids also seems to provide some relief. Operative treatment is indicated when pain is no longer tolerable and affects the patient's quality of life and when MRI reveals stenosis. The standard procedure is decompression laminectomy involving all levels determined to be compressed by preoperative imaging studies. An arthrodesis can be done if there is any deformity. Complications are often determined by the patient's overall health status and comorbidities such as cardiopulmonary disease, diabetes and kidney disease. Complication rates are higher in patients over 80 years of age.
The authors conclude that patients require careful screening for surgery because postoperative patient dissatisfaction is associated with poor preoperative functional status, the presence of multiple comorbidities and the predominance of back pain.
editor's note: Decisions about surgery are generally based on the presence of persistent pain or the development of neurologic impairment. The shift from nonsurgical treatment to surgery requires consideration of the patient's perceptions and understanding of the problem. The best likelihood of achieving an acceptable result occurs when the physician and the patient share in the decision-making process.—r.s.