What is spinal stenosis?

What is Spinal Stenosis?

Spinal stenosis is a narrowing of the spinal canal, lateral recess, or intervertebral foramen that results in mechanical compression of neural elements (nerve roots, cauda equina, or spinal cord) and their blood supply, leading to a clinical syndrome of pain, weakness, and neurological dysfunction. 1, 2

Anatomical Definition

• The normal sagittal diameter of the lumbar spinal canal measures 15-25 mm, with measurements below 12 mm confirming stenosis 3
• Lateral recess height less than 2 mm is diagnostic of stenosis 3
• Stenosis can be local (single segment), segmental (multiple levels), or generalized throughout the spine 3
• The narrowing may involve bony structures (vertebral bodies, laminae, pedicles, facet joints) or soft tissues (ligamentum flavum, disc material, osteophytes) 2, 4

Clinical Presentation by Location

Lumbar Spinal Stenosis:

• Neurogenic claudication: leg pain, weakness, or numbness with walking/standing that improves with sitting or forward flexion 1, 5
• Low back pain with or without radiculopathy (sciatica radiating below the knee) 1, 6
• Weakness, reflex alterations, and gait disturbances 4
• Bowel or bladder dysfunction in severe cases (cauda equina syndrome) 1, 4

Cervical Spinal Stenosis:

• Myelopathy: gait disturbances, balance problems, fine motor skill deterioration in hands 7, 8
• Radiculopathy: radiating pain, numbness, or tingling in the arms 7, 8
• Upper and/or lower extremity weakness due to cord compression 7, 8
• Bowel or bladder dysfunction in advanced cases 7, 8

Classification Systems

By Etiology:

• Congenital-developmental: thickened laminae, short pedicles, decreased canal diameter present from birth 3, 2
• Acquired: degenerative changes (most common), disc herniation, osteophyte formation, ligamentum flavum hypertrophy, spondylolisthesis, post-surgical (iatrogenic) 1, 3, 2

By Location:

• Central canal stenosis: compression of the thecal sac, typically causing neurogenic claudication 2
• Lateral recess stenosis: compression of individual nerve roots, causing radiculopathy 2
• Foraminal stenosis: narrowing of the intervertebral foramen where nerve roots exit 2

By Associated Deformity:

• Stenosis with spondylolisthesis (vertebral slippage) 1, 2
• Stenosis with scoliosis (spinal curvature) 1, 2
• Stenosis without deformity 1

Critical Diagnostic Considerations

• Radiographic stenosis does not equal symptomatic stenosis: anatomic narrowing on imaging is extremely common in asymptomatic older adults 1, 6, 2
• The diagnosis requires correlation of clinical symptoms, physical examination findings, and radiological changes 5, 6
• MRI is the gold standard for evaluating both osseous structures and neural elements 9
• Cord signal changes on T2-weighted MRI (hyperintensity) indicate myelopathy and suggest more severe disease 7, 8

Natural History

• The disease course is variable with stepwise decline interspersed with long periods of stability 7, 9
• Approximately 20-30% of conservatively managed patients ultimately require surgery 9
• Untreated severe cervicomedullary compression carries a 16% mortality rate 7, 8
• Prolonged severe stenosis can cause demyelination of white matter and potentially irreversible neurological deficits 7, 9, 8

Treatment Principles

Conservative Management:

• Indicated for mild to moderate symptoms without progressive neurological deficits 5, 6
• Includes patient education, pain medication, physiotherapy, epidural injections 5
• Close neurological monitoring is mandatory, as any progression mandates surgical referral 9

Surgical Indications:

• Progressive neurological deficits 7, 9
• Cord signal changes or syringomyelia on MRI 7, 9
• Cauda equina syndrome (absolute indication) 1, 9, 5
• Severe symptoms unresponsive to 3-6 months of conservative treatment 5
• Clinically relevant motor deficits 5

Surgical Outcomes:

• Approximately 97% of patients experience some symptom recovery after surgery 1, 7, 9
• Decompression with fusion provides superior long-term outcomes compared to decompression alone for pain relief, functional improvement, and quality of life 1, 7, 9
• Laminectomy alone carries higher reoperation risk due to restenosis, adjacent-level stenosis, and postoperative deformity 1, 7

Common Pitfall

The most critical error is assuming that radiographic stenosis requires treatment—asymptomatic radiographic stenosis does not warrant intervention 1. Treatment decisions must be based on the clinical syndrome, not imaging findings alone, as anatomic narrowing is ubiquitous in aging populations without causing symptoms 6, 2.