Lumbar Spinal Stenosis

Overview

Lumbar spinal stenosis is a narrowing of the spaces within the lower spinal canal that house the nerve roots, which crowds and compromises those neural structures. Narrowing can occur in the central canal, in the lateral recess where a nerve root descends, and in the neural foramen where a root exits. Most cases are degenerative: the result of disc bulging, facet-joint and bone-spur enlargement, and thickening of the ligamentum flavum accumulating over decades. It is predominantly a condition of older adults and one of the most common reasons for spine surgery after age 65.

What causes it

The narrowing impairs both the drainage and the blood supply of the nerve roots, especially when the canal narrows further during standing and extension, which is why symptoms are so posture-dependent. People born with congenitally short pedicles have a smaller baseline canal, so even modest degenerative change can become symptomatic. Recognized risk factors include advancing age, prior lumbar disc disease, degenerative spondylolisthesis (more common in women), prior spine surgery, obesity, and mechanical loading. Because spondylolisthesis frequently coexists, instability often accompanies the stenosis and influences treatment.

Symptoms and warning signs

The hallmark is neurogenic claudication: buttock, thigh, and calf discomfort, heaviness, or tingling brought on by standing and walking and relieved by sitting or leaning forward. Patients often walk farther uphill or on a bicycle, postures that flex the spine and open the canal. Narrowing of the lateral recess or foramen can also cause a radiculopathy down a specific nerve distribution. At rest the physical exam is often unremarkable.

Red-flag presentations must be excluded: cauda equina syndrome (saddle numbness, urinary retention or incontinence, bowel incontinence, and weakness in both legs) demands emergency imaging and decompression, while fever, night pain, immunosuppression, IV drug use, or a cancer history should raise concern for infection or malignancy.

How it's diagnosed

Diagnosis rests on correlating a compatible history with confirmatory imaging, since asymptomatic stenosis is common and imaging alone is not enough. MRI is preferred, showing canal, lateral recess, and foraminal narrowing and the level and severity of compression without radiation. CT, particularly CT myelography, helps when MRI cannot be done or when bony detail is needed. Standing and flexion-extension X-rays identify spondylolisthesis and instability that can change the surgical plan. Distinguishing stenosis from its mimics matters: vascular claudication eases with standing still rather than sitting; hip arthritis causes groin pain with limited hip rotation; and peripheral neuropathy causes stocking-pattern numbness that is not posture-dependent.

Treatment options

Initial management is conservative for most patients: activity modification, supervised physical therapy emphasizing flexion-based exercises and core conditioning, anti-inflammatory and other analgesic medication, and weight management. Epidural steroid injections may offer temporary relief and can help confirm the symptomatic level, though long-term benefit is modest.

When surgery is considered

Surgery is considered for persistent or progressive disabling symptoms despite an adequate trial of non-operative care, and urgently for cauda equina syndrome or a rapidly progressive deficit. The standard operation is a decompressive laminectomy, sometimes performed with minimally invasive or laminotomy techniques to preserve stability. When significant spondylolisthesis, scoliosis, or instability accompanies the stenosis, decompression is often combined with instrumented fusion. Decompression generally gives good relief of leg-dominant symptoms in well-selected patients.