What is Spinal Stenosis?
Spinal stenosis is a narrowing of the spinal canal that results in bony constriction of the cauda equina and emerging nerve roots, potentially causing compression of neural and vascular structures 1.
Anatomical Definition
Spinal stenosis represents the physical narrowing of hollow spaces within the spine—specifically the central lumbar spinal canal, lateral recess, or neural foramen 2. This narrowing occurs through a combination of bone and soft tissue changes that mechanically compress spinal nerve roots or the dural sac 3.
Pathophysiology
The condition primarily develops through degenerative changes, including:
- Ligamentum flavum hypertrophy (thickening of the ligament along the back of the spinal canal)
- Facet joint osteoarthritis (wear-and-tear arthritis of the small joints in the spine)
- Intervertebral disc degeneration (breakdown of the cushioning discs between vertebrae)
- Disc protrusion and bulging 4, 5
Additional contributing factors include genetic predisposition, congenital abnormalities (present from birth), and autoimmune conditions 4.
Clinical Presentation
The hallmark symptom is neurogenic claudication—leg pain and occasionally weakness that occurs with walking or standing, relieved by sitting or bending forward (spinal flexion) 1.
The classic symptom pattern includes:
- Low back pain radiating to buttocks and lower extremities, typically bilateral
- Burning or cramping pain that worsens with standing and walking
- Pain that improves with forward bending or sitting 6
- Paresthesia (tingling/numbness) and lower extremity weakness 4
- In severe cases: gait disturbances, bowel or bladder dysfunction, motor and sensory changes 3
Epidemiology
Lumbar spinal stenosis affects over 103 million people worldwide and approximately 11% of US adults, with prevalence increasing with age 7. It primarily affects individuals over 65 years old 5 and has a mean age of onset around 64 years 6. The condition is the leading cause of low back pain and functional limitations in older populations 4.
Critical Distinction
Not all anatomical narrowing causes symptoms—the term "lumbar spinal stenosis" refers to the clinical syndrome of lower extremity pain caused by mechanical compression, not merely the radiographic finding of canal narrowing 2. Degenerative changes on imaging correlate poorly with symptoms and are considered nonspecific 1.
Diagnostic Confirmation
The diagnosis combines clinical history with cross-sectional imaging. MRI is the preferred diagnostic modality because it provides superior visualization of soft tissue, vertebral marrow, and spinal canal patency 1, 7. CT can also confirm the presence of cauda equina compression when MRI is unavailable 8.