Lumbar Canal Stenosis: Start with Nonsurgical Therapy

•Though nearly all people in this age group have radiographic evidence of degenerative disc and joint disease, the incidence of clinically symptomatic lumbar canal stenosis is unknown.

•The diagnosis is largely clinical. Although imaging studies can confirm the diagnosis, they often show abnormalities in people with no symptoms.

•Treatment is mostly empiric. Although lumbar canal stenosis is the most common reason for spinal surgery in this aging population, (2) and accounts for inpatient expenses approaching $1 billion per year, (3) no comparison of surgical vs nonsurgical treatment has ever been done.

Even though most studies show that surgery provides the most benefit over the long term, a substantial number of people improve with nonsurgical therapy, such as physical therapy, analgesics, and NSAIDs. We recommend an initial nonsurgical treatment approach for most patients.

Definition and Classification

Lumbar canal stenosis is a narrowing or stricture of the spinal canal, with potential for nerve impingement, which may occur in the central canal, in the lateral recess, or at the neuroforamen (4,5). The cause of spinal canal narrowing may be multifactorial. Degenerative changes are typically involved, including facet joint hypertrophy, ligamentum flavum thickening, and disc bulging and protrusion, alone or in combination. Degenerative spondylolisthesis, a distinct clinical feature characterized by forward displacement of a vertebra due to disc and facet degeneration, is another frequent factor, further compromising the diameter of the spinal canal (6).

The classification of spinal stenosis proposed by Arnoldi, Brodsky, and Cauchoix6 in 1976 remains useful. In this scheme, based on the presumed etiology, spinal stenosis is classified as either congenital or acquired (Table 1). Alternatively, spinal stenosis can be classified on the basis of the location of the anatomic narrowing, ie, central canal stenosis or lateral recess stenosis.

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Table 1
Classification of spinal stenosis

Congenital stenosis
Idiopathic
Achondroplastaic

Acquired stenosis
Degenerative
Combined congenital and degenerative
Spondylolisthetic/spondyltic
Estrogenic
Post-traumatic
Miscellaneous: Paget disease, Fluorosis, Tumors, Infection
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Clinical Presentation

Recognition of spinal stenosis depends primarily on the description of the leg symptoms. Physical examination occasionally demonstrates neurologic deficits or exacerbation of symptoms with spinal positioning. However, many patients with spinal stenosis have no abnormal findings on examination.

Spinal imaging confirms the clinical impression. Because many people who have no symptoms are found to have radiographic abnormalities, clinical correlation is critical.

History
Spinal stenosis typically affects persons over 50 years of age (7). It is uncommon in younger people unless they are anatomically predisposed by a congenitally narrowed canal, previous spine trauma or surgery, spondylolisthesis, or even scoliosis.

The classic symptom of central canal stenosis is pseudoclaudication, also known as neurogenic claudication (1,3,4,7,8). Patients typically complain of pain, paresthesia, weakness, or heaviness in the buttocks radiating into the lower extremities with walking or prolonged standing, relieved with flexion or sitting. Though many patients have significant lumbar pain due to degenerative joint and disc changes, most have more lower extremity discomfort rather than spinal pain.

The most important aspect of neurogenic claudication is the relationship of symptoms to posture. Symptoms occur with spinal extension and are relieved in flexion. Patients usually have no symptoms or have minimal discomfort when seated or supine. They can walk longer distances with less pain in a forward flexed position, such as when using a grocery cart while shopping (the "grocery cart sign"). They may be able to exercise using a stationary bicycle in the seated flexed position for a much longer time (the bicycle test of Van Gelderen) than when walking in the erect position on a treadmill.

In a review of 68 patients with myelographically proven, surgically confirmed spinal stenosis, (8) the most common symptoms were pseudoclaudication and standing discomfort (94%), followed by numbness (63%) and weakness (43%). Symptoms were bilateral in 68%. Discomfort was felt both above and below the knee in 78%, in the buttocks or thigh only in 15%, and below the knee in 7%.

Historic features correlating most strongly with a confirmed diagnosis of spinal stenosis (likelihood ratio greater than or equal to 2) include age greater than 65 years, severe lower extremity pain, and absence of pain when seated (9).

Physical examination
The physical examination in patients with lumbar canal stenosis is frequently normal or demonstrates only nonspecific findings.

Many older people have reduced spinal mobility, with or without spinal canal stenosis. Extension is usually more limited than flexion (10,11).

Patients with stenosis often have lumbar, paraspinal, or gluteal tenderness, probably related to underlying degenerative changes, muscle spasms, and poor posture. Some assume a characteristic "simian stance," with their hips and knees slightly flexed and the trunk stooped forward (7). This semiflexed posture allows patients to stand or walk for longer distances.

Hamstring tightness is often present and may produce a false-positive straight leg-raise test.

The neurologic examination typically is normal or reveals only subtle abnormalities such as mild weakness, sensory changes, and reflex abnormalities. This is particularly true if the patient has rested in the seated position before the physical examination begins. These subtle findings may be unmasked if the patient is examined after walking until developing leg and buttock symptoms similar to the presenting complaint (4).

Ankle reflexes are diminished in 43% to 65% of patients, while knee reflexes are abnormal in 18% to 42% (9,11). The straight leg raising test and other nerve root tension signs are usually negative unless there is concomitant disc herniation.

A careful motor examination should be done. Leg weakness is generally mild and overwhelmingly in the distribution of the L4, L5, or S1 nerve roots. Objective evidence of subtle weakness can usually be demonstrated in about 50% of persons with spinal stenosis (2). Weakness of the muscles innervated by the L5 nerve root is the most common finding, (4) and weakness of great toe extensors (extensor hallucis longus) and hip abductors should be sought, the latter by the Trendelenburg test (4).

The Trendelenburg test is performed by having the patient stand on one leg: if the gluteus medius is not functional or is denervated, the pelvis drops on the side opposite the damaged muscle. This is shown clinically by an abnormal, waddling gait called the "Trendelenburg gait," caused by trying to compensate for a drooping pelvis.

The gait should be carefully observed. Difficulty in walking on the toes suggests S1 root involvement. Difficulty with heel walking suggests L4 or L5 nerve dysfunction.

Sensory abnormalities may be present in 46% to 51% of preoperative spinal stenosis patients (2,10).

Katz et al (9) found a positive lumbar extension test to be strongly predictive of imagingconfirmed spinal stenosis. This test is performed by asking the standing patient to hyperextend the lumbar spine for 30 to 60 seconds. A positive test is defined by reproduction of the buttock or leg pain.