Sciatica - Clinical Notes

Definition

• Symptom to Diagnosis, 4th Ed.

Epidemiology

• Lifetime prevalence of true sciatica: 2-4% (contrast with low back pain: 60-80%)
• 90% of acute low back pain resolves within 6 weeks
• 70% of acute sciatica episodes resolve within 3 months
• 5-7% of the population aged 45-64 years report back problems as a chronic sickness
• Bailey and Love's Short Practice of Surgery, 28th Ed.

Anatomy

• Superiorly and inferiorly by pedicles
• Anteriorly by the disc
• Posteriorly by the facet joint

• Bailey and Love's; Adams and Victor's Principles of Neurology, 12th Ed.

Causes / Etiology

Neurogenic - within the spine (Spondylotic):

• Herniated nucleus pulposus
• Stenosis of central canal, lateral recess, or intervertebral foramen
• Synovial cyst (from degenerative facet joint disease)
• Arachnoid or perineural (Tarlov) cysts
• Sterile inflammatory arachnoiditis
• Tumor: primary (neurofibroma, ependymoma) or metastatic (bone/epidural/meningeal)
• Infection: disc, epidural, herpes zoster, Lyme disease
• Inflammatory radiculopathy (sarcoidosis, paraneoplastic)

Neurogenic - outside the spine:

• Lumbosacral plexus involvement
• Sciatic neuropathy
• Peripheral neuropathy

Non-neurogenic:

• Musculoskeletal (hip arthritis, trochanteric bursitis, sacroiliac joint disease, piriformis syndrome, iliotibial band syndrome, hamstring tendinitis)
• Peripheral vascular disease

Special/rare causes:

• Piriformis syndrome - the sciatic nerve passes under (or occasionally through) the piriformis muscle; spasm or hypertrophy may compress it. Pain is elicited by hip flexion, adduction, and internal rotation.
• Catamenial sciatica - temporally linked to the premenstrual period; almost always due to endometriosis at the sciatic notch.
• Pregnancy-related sciatica - uterine traction on the nerve.
• Cauda equina compression from epidural tumor (prostate/breast cancer, myeloma), lymphoma, or inflammatory conditions (CMV in AIDS, Lyme disease/Bannwarth syndrome, herpetic infection, neoplastic meningitis, Guillain-Barre).
• Goldman-Cecil Medicine; Adams and Victor's; Tintinalli's Emergency Medicine

Disc Herniation - Key Points

• 95% of clinically important herniations occur at L4-L5 and L5-S1
• A smaller proportion (often elderly) occurs at L2-L3 and L3-L4
• Pain and paresthesias follow the dermatomal distribution of the affected root
• Radicular pain is typically described as sharp, shooting, burning, throbbing, or tingling
• Contact of the disc with a nerve root provokes inflammation - this (not just mechanical compression alone) drives symptoms

Nerve Root Levels - Clinical Findings

• Symptom to Diagnosis, 4th Ed.

Clinical Features

• Pain radiating from the back down the buttock and leg, typically to the foot or ankle
• Associated numbness or paresthesias in a dermatomal distribution
• Pain classically worsened by coughing, sneezing, or sudden increases in intra-abdominal/intraspinal pressure (Naffziger sign)
• Radicular pain is a more prominent complaint than back pain in disc herniation
• Pain precipitated or worsened by forward bending, lifting

• Antalgic posture (sciatic scoliosis) - reflex paraspinal muscle contraction; knee slightly flexed on affected side
• When disc herniates lateral to the nerve root: trunk bends toward side of lesion; medial to root: bends away
• Walking is cautious with brief weight bearing and a limp
• Knee slightly flexed to relax hamstrings

Straight Leg Raise (SLR) - Lasègue Sign

• Patient supine; examiner raises the straight leg
• Positive test: Reproduces sciatic pain (shooting down the leg) when the leg is elevated between 30-60 degrees
• Sensitivity: 72-97%, Specificity: 11-66%
• When sciatica is reproduced: Sensitivity 95%, Specificity 88%, LR+ 7.9, LR- 0.06

Crossed SLR (Fajersztajn Sign)

• Raising the contralateral straight leg reproduces pain on the affected side
• More specific but less sensitive for herniated disc than the ipsilateral SLR
• Sensitivity 25%, Specificity 90%

Other signs:

• Bragard sign - dorsiflexion of the foot accentuates SLR pain
• Sicard sign - dorsiflexion of the great toe accentuates pain
• Neri sign (standing) - forward trunk bending causes knee flexion on the affected side
• Valleix points - pressure along the sciatic nerve course (sciatic notch, retrotrochaneric gutter, posterior thigh, head of fibula) reproduces radiating pain
• Adams and Victor's; Goldman-Cecil; Symptom to Diagnosis; Rosen's Emergency Medicine

Investigations

Imaging

• MRI is the preferred modality (gold standard for soft tissue/disc detail)
• Non-urgent MRI for most cases of suspected disc herniation
• Urgent/emergent MRI if suspected: epidural compression, cauda equina syndrome, rapid progressive neurologic deficit, or red-flag features
• Plain radiographs: useful if tumor, fracture, spondylolisthesis, or infection is suspected
• If symptoms are not severe or rapidly progressive, MRI can be ordered routinely rather than emergently

Electrodiagnostics (EMG/NCS)

• Needle EMG is the most sensitive EDX tool in suspected lumbosacral radiculopathy
• Fibrillation potentials are the most objective finding - confirm denervation in a segmental myotomal distribution with normal SNAP in the corresponding dermatome
• EMG may be normal if only the dorsal root is compressed (pain/paresthesias only, no motor involvement)
• EMG and imaging are complementary: EMG = nerve root function; imaging = anatomy
• Bradley and Daroff's Neurology in Clinical Practice; Goldman-Cecil; Tintinalli's

Cauda Equina Syndrome - Red Flag

• Low back pain
• Uni- or bilateral sciatica
• Saddle anaesthesia
• Motor weakness in the lower extremities
• Variable rectal and urinary symptoms

• Goldman-Cecil; Bailey and Love's

Treatment

Conservative (first-line for most patients)

• Activity: Routine daily activity is as effective as 2 weeks of bed rest. Early mobilization accelerates recovery; prolonged immobilization is detrimental.
• Analgesics: NSAIDs are first-line (though less effective for disc herniation than non-specific back pain); limited opioids for severe pain
• Note: Most sufferers of acute sciatica recover within 6 weeks using simple nonoperative therapy

Medications with limited/no evidence:

• Oral corticosteroids - no lasting measurable benefit in sciatica
• Muscle relaxants - insufficient evidence
• Antiepileptics/anticonvulsants - insufficient evidence; pregabalin is not helpful for acute or chronic sciatica
• Antidepressants - studies find little benefit

Epidural Corticosteroid Injections (ESI)

• Provides a minor reduction in leg pain and sensory deficits vs. placebo at 2-6 weeks
• No significant functional benefit; does not reduce the need for surgery
• Not an emergency department procedure; option for moderately-to-severely symptomatic patients at follow-up
• No proven longer-lasting value beyond 6 weeks

Physical therapy / Spinal manipulation

• Spinal manipulative therapy results in a small decrease in pain up to 12 weeks
• Back-strengthening exercises help chronic cases

Surgery - Indications (all three criteria must be met):

1. Definitive evidence of herniation on imaging
2. Corresponding clinical picture and neurologic deficit
3. Failure of adequate conservative therapy

• Tintinalli's; Bradley and Daroff's; Goldman-Cecil

Prognosis

• Most patients with herniated disc improve with nonsurgical therapy
• Over 50% recover in 6 weeks
• Workers off work for >6 months have a guarded prognosis for return to work
• Recurrent disc herniation or incomplete discectomy are common causes of poor post-operative outcomes

Recent Evidence (PubMed, 2024-2026)

• A 2024 systematic review of clinical practice guidelines (PMID: 38629664) synthesised medication recommendations for lumbosacral radiculopathy - useful for checking current drug guidance.
• A 2025 meta-analysis (PMID: 40488872) examined how symptom duration before lumbar discectomy affects outcomes - earlier surgery may yield better results.
• A 2024 systematic review (PMID: 38190195) assessed diffusion tensor MRI for lumbosacral nerve root evaluation - a potentially useful advanced imaging tool.

Disc Herniation Anatomy - Clinical Images

1. Central vs. Posterolateral Disc Herniation (Axial Anatomy)

2. Sagittal MRI - Large Lumbar Disc Herniation

3. Disc Herniation Types - Protrusion vs. Extrusion (Axial Schematic)

• (A) Broad-based protrusion - base broader than apex, >25% of disc circumference involved
• (B) Focal protrusion - base broader than apex, <25% of disc circumference
• (C) Extrusion - base narrower than the apex ("toothpaste sign"); an extrusion is rarely seen in asymptomatic patients

4. Herniation Location Classification (Axial Plane)

• (A) Central - posterior midline; risks cauda equina syndrome
• (B) Paracentral - right or left of midline; most common cause of sciatica
• (C) Subarticular / lateral recess - compresses traversing nerve root in the lateral recess
• (D) Foraminal - within the neural foramen, compresses exiting nerve root
• (E) Extraforaminal - outside the neural foramen; far lateral, compresses the exiting nerve root one level higher than expected
• (F) Anterior - rare, usually asymptomatic

5. Massive Disc Extrusion - MRI (Sagittal + Axial T2)

• Displacement of nerve roots
• Obliteration of the left lateral recess
• Loss of disc height at L3-L4
• Decreased disc signal at L4-L5 (early degenerative change)

6. Foraminal Disc Protrusion - CT (Sagittal + Axial, Bone and Soft Tissue Windows)

• (A, B) Broad-based foraminal disc protrusion on the left at L4-L5 with a calcified outer rim (bone window)
• (C, D) Broad-based disc protrusion on the right at L5-S1 (soft-tissue window) This demonstrates how CT can identify calcified fragments and foraminal compromise.

7. Sequestrated Disc Fragment with Gadolinium Enhancement - MRI

• (A, B) Precontrast sagittal and axial T1
• (C, D) Post-gadolinium: peripheral rim enhancement around the fragment
• Clinical pearl: Peripheral contrast enhancement is associated with a high probability of spontaneous regression - an important prognostic indicator

8. CT Myelography of Lumbar Disc Herniation at L4-5 (Multiple Views)

• (A) Scout view (angled gantry technique)
• (B) Scout view (straight gantry)
• (C) Cross-sectional axial CT at L4-5 disc level - normal soft tissue anatomy
• (D) Sagittal and coronal reformats (computerized reformatted technique)
• (E) Axial CT 2 hours after metrizamide myelography - contrast outlines the thecal sac, clearly delineating the herniation
• (F) Axial CT after IV contrast injection for greater soft-tissue differentiation

Key Anatomical Points Illustrated