Lumbar Spinal Stenosis

• The hallmark is neurogenic claudication (pseudoclaudication): bilateral buttock, thigh and leg pain, heaviness or paraesthesia brought on by standing and walking and relieved by sitting or leaning forward.
• Flexion opens the canal, which explains the classic findings: relief when leaning on a shopping trolley ("shopping cart sign"), better tolerance of walking uphill or cycling than walking downhill or on the flat, and comfort when sitting.
• Distinguishing vascular claudication is a standard exam task: vascular claudication is relieved by standing still (position irrelevant), worsens uphill, is associated with absent pulses, hair loss and cool skin, and has a reproducible walking distance. Neurogenic claudication requires flexion, not merely rest, and pulses are normal.
• Examination is often unremarkable at rest, which is itself a clue; symptoms may be reproducible after walking.
• Imaging: MRI defines the level and severity, but degenerative changes are near-universal in older adults — imaging must be correlated with the clinical picture.
• Management: physiotherapy focused on flexion-based exercise, analgesia, and weight reduction. Epidural corticosteroid injection gives limited and temporary benefit. Decompressive laminectomy, with fusion where there is instability or spondylolisthesis, is offered for disabling symptoms refractory to conservative care or for progressive neurological deficit.

Degenerative (acquired) — the overwhelming majority

• Facet joint osteoarthritis: cartilage loss and osteophytosis hypertrophy the superior articular process, encroaching on the lateral recess where the traversing root sits.
• Ligamentum flavum thickening and buckling: chronic loading causes fibrosis and loss of elastin; the ligament infolds dorsally into the canal, especially in extension.
• Disc degeneration: loss of disc height causes circumferential bulging and segmental instability, which in turn drives facet and ligament hypertrophy — a self-reinforcing cycle.
• Degenerative spondylolisthesis: most classically at L4–L5, more common in older women; anterior slip of the vertebral body telescopes the canal.

Congenital / developmental

• Short pedicles with a constitutionally narrow canal: symptoms appear a decade or two earlier because minimal degenerative change exceeds the reserve space.
• Achondroplasia: the classic named cause, from premature ossification producing short pedicles and a trefoil canal.

Other structural causes examiners plant

• Paget disease of bone: expanded, disorganised woven bone narrows the canal; look for elevated alkaline phosphatase with normal calcium and phosphate.
• Spinal epidural lipomatosis: overgrowth of epidural fat with exogenous glucocorticoids, Cushing syndrome or obesity.
• Ossification of the posterior longitudinal ligament or ligamentum flavum, DISH, ankylosing spondylitis, post-traumatic or post-surgical scarring, and acromegaly.

Non-modifiable risk factors

• Age: prevalence rises steeply after the sixth decade — degeneration is cumulative.
• Congenitally narrow canal and female sex (for degenerative spondylolisthesis specifically).

Modifiable risk factors

• Obesity: increases axial load and is independently associated with epidural lipomatosis and worse symptoms.
• Smoking: accelerates disc degeneration through impaired endplate perfusion.
• Occupational heavy lifting, vibration exposure and repetitive axial loading.
• Chronic systemic glucocorticoid use (epidural lipomatosis).
• Deconditioning and weak trunk extensors, which worsen sagittal balance and function even when canal dimensions are unchanged.

• Loss of canal reserve volume is the initiating insult: facet hypertrophy, ligamentum flavum infolding, disc bulging and any spondylolisthesis together reduce the cross-sectional area available to the cauda equina and to the roots in the lateral recess. The canal is a fixed compartment, so encroachment raises pressure on its contents.
• Cauda equina roots are uniquely vulnerable because they lack the protective epineurium of peripheral nerves and depend on a delicate radicular arterial supply plus a low-pressure venous drainage network within the CSF.
• Venous congestion precedes arterial ischaemia: modest compression first obstructs epidural and intraneural venous outflow. Stasis raises intraneural capillary pressure, produces endoneurial oedema, and impairs the axonal nutrition supplied by CSF flow along the roots.
• Symptoms are demand-dependent, which is why they are exertional. Walking increases the metabolic demand of the lumbosacral roots; the congested, compressed segment cannot increase blood flow to match, and relative ischaemia produces the pain, heaviness and paraesthesia of neurogenic claudication — the neural analogue of angina.
• Posture changes the calibre of the canal, and this drives the entire clinical picture:
• Extension (standing, walking downhill, lying prone) shortens the spinal column, buckles the ligamentum flavum inward, telescopes the facets and increases disc bulge — canal area falls and symptoms appear.
• Flexion (sitting, leaning on a trolley, cycling, walking uphill) tensions the ligamentum flavum, distracts the facets and increases canal cross-sectional area — venous outflow resumes and symptoms remit within minutes.
• Multilevel stenosis compounds the deficit through a double-crush effect: two compressed segments impair blood flow to the intervening root segment far more than either alone.
• Chronic compression causes structural change: demyelination, then axonal loss with fibrosis, explaining fixed weakness, reflex loss and sphincter dysfunction in advanced disease.
• Lateral recess or foraminal stenosis produces unilateral radicular pain rather than the bilateral pseudoclaudication of central stenosis, because a single traversing or exiting root is compressed.

Classic symptoms

• **Neurogenic claudication (pseudoclaudication)**: bilateral, often asymmetric buttock, posterior thigh and calf pain, heaviness, cramping or paraesthesia provoked by standing and walking — root ischaemia under increased metabolic demand.
• Relief with flexion, not merely rest: sitting, squatting or leaning forward opens the canal. Patients describe relief while leaning on a supermarket trolley (shopping cart sign) and better tolerance of walking uphill or cycling than of walking on the flat.
• Delayed relief: minutes are needed for venous congestion to resolve, unlike the near-immediate relief of vascular claudication on stopping.
• Symptoms are proximal-to-distal in spread and vary day to day; walking distance is inconsistent, whereas vascular claudication has a reproducible threshold.
• Radicular pain in a single dermatome suggests lateral recess or foraminal stenosis; L5 and S1 roots are most often involved.
• Nocturnal calf cramps and lower limb numbness are common; some patients report a sensation of walking on cotton wool.

Examination findings

• Often normal at rest — a normal neurological examination in a patient with dramatic walking limitation is itself the clue.
• Wide-based, cautious gait and impaired tandem walking, reflecting proprioceptive root involvement.
• Reduced lumbar extension reproduces symptoms; flexion relieves them. Sustained extension for 30–60 seconds may provoke leg symptoms in clinic.
• Diminished ankle reflexes and patchy sensory loss in longstanding disease; motor weakness (extensor hallucis longus, ankle dorsiflexion) is usually mild and late.
• Normal, palpable pedal pulses with warm, hair-bearing skin — the finding that separates this from peripheral arterial disease.
• Negative straight-leg raise in central stenosis, unlike acute disc herniation.

• The diagnosis is clinical: a history of exertional, posture-dependent bilateral leg symptoms relieved by flexion, with preserved pulses, is sufficient to begin conservative care. NASS emphasises correlation of imaging with history and examination.

Initial evaluation

• No imaging in the first six weeks in the absence of red flags. The ACP low back pain guideline and Choosing Wisely both advise against early imaging, because degenerative canal narrowing is present in a large proportion of asymptomatic older adults — imaging alone cannot make the diagnosis.
• Ankle–brachial index when vascular claudication is plausible; per the ACC/AHA peripheral artery disease guideline an ABI of 0.90 or less establishes PAD, and a normal ABI at rest with a suggestive history warrants exercise ABI testing.
• Plain radiographs, including flexion–extension views, when spondylolisthesis or instability is suspected; upright films reveal slips that supine cross-sectional imaging misses.
• Laboratory studies only to pursue alternatives — ESR/CRP for infection or malignancy, alkaline phosphatase for Paget disease, HbA1c and B12 for polyneuropathy.

Confirmatory imaging

• MRI lumbar spine without contrast is the test of choice and is the American College of Radiology's preferred study; it shows the ligamentum flavum, facet and disc contributions, and root crowding. Add contrast only for prior surgery (scar versus recurrent disc), infection or tumour.
• CT myelography is the alternative when MRI is contraindicated (pacemaker, retained hardware causing artefact) and is often preferred for surgical planning in instrumented spines.
• Characteristic findings: loss of anterior CSF space with a trefoil canal, redundant or serpiginous nerve roots above the stenosis, and buckled ligamentum flavum. Classically taught thresholds are an anteroposterior canal diameter under about 10 mm for absolute and 10–12 mm for relative stenosis, though no dimension is diagnostic in isolation.
• Electrodiagnostic studies are reserved for distinguishing stenosis from peripheral polyneuropathy or a focal mononeuropathy, not for routine confirmation.
• Urgent MRI for suspected cauda equina syndrome — do not defer for conservative therapy.

Immediate triage

• Cauda equina syndrome or rapidly progressive motor deficit mandates emergent MRI and urgent surgical decompression — do not treat conservatively.

First-line (non-operative), for the large majority

• Structured physiotherapy with flexion-based exercise: pelvic tilts, stationary cycling, core and hip extensor strengthening. Mechanistically, flexion postures enlarge the canal; conditioning also raises the ischaemic threshold. NASS supports active exercise-based therapy.
• NSAIDs (e.g. naproxen) as the pharmacologic first choice; the ACP guideline places nonpharmacologic therapy first with NSAIDs as the initial drug class for back pain. Use with caution in older adults given renal, GI and cardiovascular risk.
• Duloxetine is the ACP second-line pharmacologic option for chronic back pain.
• Weight reduction and smoking cessation address load and disc perfusion.
• Acetaminophen has not shown benefit for back pain and gabapentinoids are not supported for stenosis or radicular pain — a common exam distractor.
• Opioids should be avoided for this chronic, non-malignant condition; the CDC opioid prescribing guideline advises nonopioid therapy as preferred.

Escalation

• Epidural corticosteroid injection may give short-lived relief in radicular pain but offers limited durable benefit for neurogenic claudication and does not alter the need for surgery; NASS regards evidence for sustained benefit as weak.
• Calcitonin is not effective and should not be used.

Definitive management

• Decompressive laminectomy for disabling symptoms refractory to several months of conservative care, or for progressive deficit. Surgery outperforms continued non-operative care for leg pain and walking capacity in the short to intermediate term, as shown in the SPORT trial, with convergence over longer follow-up.
• Add instrumented fusion when there is degenerative spondylolisthesis with instability, scoliosis, or when decompression itself destabilises the segment; fusion is not indicated for uncomplicated central stenosis.
• Interspinous process spacers are an option in selected patients with flexion-relieved symptoms who are poor open-surgery candidates.

Of the disease

• Progressive walking limitation and deconditioning: reduced ambulation begets sarcopenia, weight gain and cardiovascular deconditioning, which further lowers the claudication threshold.
• Falls and fragility fractures: proprioceptive root involvement and a wide-based, cautious gait raise fall risk in an already osteoporotic population.
• Fixed neurological deficit: chronic root ischaemia progresses from demyelination to axonal loss, producing persistent foot drop, sensory loss or areflexia that may not recover after decompression.
• Cauda equina syndrome — an emergency: uncommon in slowly progressive degenerative stenosis but may be precipitated by an acute central disc herniation onto a stenotic canal. Signalled by saddle anaesthesia, urinary retention with overflow incontinence, bilateral leg weakness and loss of anal tone. Requires emergent MRI and decompression; delay predicts permanent bladder dysfunction.
• Chronic pain and depression, with the functional disability of the condition.

Of injection therapy

• Dural puncture with post-dural puncture headache; rarely arachnoiditis.
• Transient hyperglycaemia and HPA axis suppression from systemic glucocorticoid absorption — relevant in diabetics.
• Epidural abscess or haematoma — emergencies: new or worsening pain with fever, or a new deficit after injection, demands urgent MRI.

Of surgery

• Incidental durotomy with CSF leak: the most common intraoperative complication of laminectomy in an elderly, adherent dura; presents as positional headache or clear wound drainage.
• Postoperative epidural haematoma — an emergency: severe pain with new bilateral weakness or retention in the first 24–48 hours; needs immediate imaging and evacuation.
• Surgical site infection, higher in diabetics, smokers and with instrumentation.
• Iatrogenic instability from excessive facet resection, sometimes requiring later fusion.
• Adjacent segment degeneration after fusion, as load transfers to the mobile neighbouring level, producing recurrent claudication years later.
• Pseudarthrosis and hardware failure after fusion; recurrent stenosis from regrowth of bone or scar.
• Perioperative medical events: venous thromboembolism, delirium and cardiac complications in an elderly cohort.

• Flexion relieves, extension provokes — the single mechanistic idea behind every buzzword. Flexion tensions the ligamentum flavum and distracts the facets, enlarging the canal. Hence the shopping cart sign, relief with sitting, and better tolerance of cycling and uphill walking (both flexed) than of walking downhill (extended).
• Neurogenic versus vascular claudication is the most tested discrimination: neurogenic requires a change in posture and resolves over minutes, with normal pulses and normal skin; vascular resolves with standing still alone, worsens uphill, has a reproducible walking distance, and comes with absent pulses, hair loss and cool skin. Order an ankle–brachial index if uncertain — ACC/AHA sets the PAD threshold at 0.90 or less.
• The best next step in a stable patient is not MRI — it is a trial of conservative therapy with flexion-based physiotherapy and an NSAID. ACP and Choosing Wisely advise against early imaging because canal narrowing is near-universal in older adults; imaging is obtained when surgery is being considered or red flags appear.
• MRI without contrast is the confirmatory study; CT myelography when MRI is contraindicated.
• A normal neurological examination at rest in a patient with striking walking limitation supports the diagnosis rather than arguing against it.
• Saddle anaesthesia, urinary retention and bilateral weakness = cauda equina syndrome: emergent MRI and surgical decompression, never a steroid injection or a physiotherapy referral.
• L4–L5 degenerative spondylolisthesis is the classic association, more common in older women; instability at this level is what converts a decompression into a decompression with fusion.
• Common distractors: gabapentinoids (not supported for stenosis), acetaminophen (ineffective for back pain), opioids (discouraged by the CDC guideline), bed rest and traction. Also do not mistake hip osteoarthritis — groin pain with limited internal rotation, unrelated to spinal posture — or diabetic polyneuropathy, which is stocking-distribution and not positional.