Lumbar spinal stenosis often presents with neurogenic claudication (NC) (claudicate: from Latin, claudico, to limp) AKA pseudoclaudication. To be differentiated from vascular claudication (AKA intermittent claudication), which results from ischemia of exercising muscles
NC characteristics: unilateral or bilateral buttock, hip, thigh, or leg discomfort that is precipitated by standing or walking and characteristically relieved by a change in posture (usually sitting with the waist flexed, squatting, or lying in the fetal position). Painful burning paresthesias of the lower extremities are also described. Valsalva maneuvers usually do not exacerbate the pain. Many patients report increased pain first thing in the morning that improves once they have been out of bed for varying periods (usually an hour more or less).
The time course is usually gradually progressive over many months to years. As the condition progresses, the ability to get relief from position changes tends to decrease. However, presenting with acute, unrelenting pain is not characteristic and other causes should be sought. In comparison, an HLD usually causes increased pain on sitting, has a more abrupt onset, has pain on straight leg raising, and is worsened by Valsalva maneuvers. NC is thought to arise from ischemia of lumbosacral nerve roots, as a result of increased metabolic demand from exercise together with vascular compromise of the nerve root due to pressure from surrounding structures. NC is only moderately sensitive (≈ 60%) but is highly specific for spinal stenosis.
Pain may not be the major complaint; instead, some patients may develop paresthesias or LE weakness with walking. Some may complain of muscle cramping, especially in the calves.
Relief from symptoms: occurs with positions that decrease the lumbar lordosis which increases the diameter of the central canal (by reducing inward buckling of the ligamentum flavum) and distracts the facet joints (which enlarges the neural foramina). Favored positions include sitting, squatting and recumbency. Patients may develop “anthropoid posture” (exaggerated waist flexion).
“Shopping cart sign” patients often can walk farther if they can lean forward e.g. as on a grocery cart. Riding a bicycle is also often well tolerated.
The neurologic exam is normal in ≈ 18% of cases (including normal muscle stretch reflexes and negative straight leg raising). Weakness in the anterior tibialis and/or extensor hallucis longus may occur in some cases of central canal stenosis at L4–5, or with foraminal stenosis of L5–1. Absent or reduced ankle jerks and diminished knee jerks are common; however, this is also prevalent in the aged population. Pain may be reproduced by lumbar extension.
Comparison of modalities
MRI: demonstrates impingement on neural structures and loss of CSF signal on T2WI due to central canal stenosis, lateral recess stenosis, foraminal stenosis as well as juxtafacet cysts, increased fluid in the facet joint and vacuum disc. MRI is poor for visualizing bone which contributes significantly to the pathology. Asymptomatic abnormalities are demonstrated in up to 33% of patients 50–70 years old without back-related symptoms.
Lumbosacral spine X-rays: may disclose spondylolisthesis. AP diameter of canal is usually narrowed (congenitally or acquired) (see below) whereas the interpediculate distance (IPD) may be normal. 16 Oblique films may demonstrate pars defects. Adding flexion/extension views can assess “dynamic“ instability.
Standing scoliosis X-rays: provide information about scoliosis and sagittal balance (see Adult degenerative scoliosis).
CT scan (either routine, or following water-soluble myelography): classically shows “trefoil” canal (cloverleaf shaped, with 3 leaflets). CT also demonstrates AP canal diameter, hypertrophied ligaments, facet arthropathy, pars fractures and occasionally may show bulging annulus or herniated disc. Myelogram: lateral films often show “washboard pattern” (multiple anterior defects), AP films often show “wasp-waisting” (narrowing of dye column), may also show partial or complete (especially in prone position) block. May be difficult to perform LP if stenosis is severe (poor CSF flow and difficulty avoiding nerve roots with the LP needle).
“Bicycle test”: patients with NC can usually tolerate longer periods of exercise on a bicycle than patients with intermittent (vascular) claudication because the position in bicycling flexes the waist. Noninvasive studies to rule out vascular insufficiency: Ratio of ankle to brachial blood pressure (A:B ratio): > 1.0 is normal; mean of 0.59 in patients with intermittent claudication; 0.26 in patients with rest pain; < 0.05 indicates impending gangrene. EMG with NCV may show multiple nerve-root abnormalities bilaterally.
Coincident symptomatic lumbar spinal stenosis and cervical spinal stenosis is usually managed by first decompressing the cervical region, and later operating on the lumbar region (unless severe neurogenic claudication).