Lumbar Disc Herniation

Lumbar disc herniation is the displacement of nucleus pulposus or annular material beyond the margins of the intervertebral disc space, which compresses and chemically irritates a lumbar or sacral nerve root and causes lumbar radiculopathy (sciatica). Most cases settle without surgery.

Sciatica affects 13 to 40% of people during life, and symptomatic herniation affects 1 to 3% of the population. It peaks between 30 and 50 years, is about twice as common in men, and 90 to 95% occur at L4 to L5 and L5 to S1. Smoking, obesity, heavy lifting, vibration, a family history and tall stature increase the risk. Herniation is also found on MRI in 20 to 36% of adults without symptoms.

Pain resolves in 60 to 80% within 6 to 12 weeks, and extruded or sequestered fragments often regress over months through resorption. Cauda equina syndrome occurs in about 1 to 3% of surgical cases. Complications are persistent radicular pain, motor weakness (foot drop), recurrent herniation, chronic back pain and cauda equina syndrome.

Pathophysiology.

Age related disc degeneration (loss of proteoglycan and water, annular fissures) and mechanical load cause protrusion, extrusion or sequestration.

The herniated material releases inflammatory mediators (TNF-alpha, interleukin-1 beta, interleukin-6, phospholipase A2) that sensitise the root, while compression causes intraneural oedema and ischaemia.

A posterolateral herniation compresses the traversing root (the L5 root at L4 to L5), a far lateral herniation compresses the exiting root (L4 at L4 to L5), and a large central herniation compresses the cauda equina.

Back pain, often preceding leg pain, followed by pain radiating distal to the knee in a dermatomal pattern, worse with sitting, coughing, sneezing and straining, and eased by standing or lying. Paraesthesia and numbness follow the root.

• L4: anterior thigh and medial leg pain; weak quadriceps; reduced knee reflex.
• L5: lateral leg and dorsum of foot pain, great toe numbness; weak ankle and great toe dorsiflexion (foot drop); normal reflexes.
• S1: posterior calf and lateral foot pain; weak plantar flexion; reduced ankle reflex.

Examine the straight leg raise (positive at 30 to 70 degrees; sensitive, with low specificity), crossed straight leg raise (specific), femoral stretch test (L2 to L4), slump test, power (grade 0 to 5), sensation, reflexes, gait (heel and toe walking), and spinal movement. Features of cauda equina syndrome: bilateral sciatica, saddle numbness, urinary retention or overflow, faecal incontinence, sexual dysfunction, and progressive weakness.

• The diagnosis is clinical. Imaging is not needed in the first 6 weeks unless warning features or a severe or progressive deficit exist.
• MRI (T2 sagittal and axial images): herniation type (protrusion, extrusion, sequestration), root compression, canal size, Modic changes, and disc degeneration grade; correlate with the clinical level.
• CT myelography when MRI is contraindicated; plain radiographs have a limited role.
• Electromyography and nerve conduction studies after 3 to 4 weeks when the level or diagnosis is unclear.
• In suspected cauda equina syndrome, emergency MRI and a post-void bladder scan (residual over 200 mL); blood tests (full blood count, ESR, CRP) when infection or cancer is suspected.

Differential diagnosis.

• Lumbar stenosis and spondylolisthesis.
• Piriformis syndrome, sacroiliac joint dysfunction and hip osteoarthritis.
• Epidural abscess, discitis, tumour and fracture.
• Herpes zoster, diabetic neuropathy, vascular claudication and peroneal neuropathy.

The first aim is to relieve pain while the herniation resolves, and to identify patients who need urgent surgery.

Non-operative treatment (first 6 to 12 weeks).

• Education and reassurance, staying active, and avoiding bed rest; physiotherapy with graded exercise and neural mobilisation once pain allows.
• Paracetamol 1 g orally every 6 hours as needed (maximum 4 g daily; 3 g daily when weight is under 50 kg, with chronic alcohol use or hepatic impairment); its effect on sciatica is small.
• Ibuprofen 400 mg orally every 8 hours with food (maximum 1200 mg daily) or naproxen 500 mg orally every 12 hours with food (maximum 1000 mg daily) for 1 to 2 weeks.
• Add omeprazole 20 mg orally once daily in patients over 65 or with ulcer risk; avoid NSAIDs with eGFR under 30 mL/min/1.73 m2, peptic ulcer, heart failure, uncontrolled hypertension or anticoagulant use.
• Neuropathic pain: amitriptyline 10 mg orally at night, increased by 10 mg every 1 to 2 weeks to 25 to 50 mg (avoid with recent myocardial infarction, arrhythmia, glaucoma, urinary retention, and caution over 65 years).
• Gabapentin 300 mg orally at night, increased by 300 mg every 1 to 3 days to 300 to 600 mg three times daily (maximum 3600 mg daily; reduce at creatinine clearance under 60 mL/min).
• Or pregabalin 75 mg orally at night or twice daily, increased to 150 mg twice daily (maximum 300 mg twice daily; reduce with renal impairment). Evidence of benefit in sciatica is limited.
• Short course opioid for severe pain: oral morphine 5 to 10 mg every 4 hours as needed for up to 5 to 7 days (start 2.5 to 5 mg with age over 75 or eGFR under 30 mL/min/1.73 m2); laxative; avoid long term use.
• Acute severe muscle spasm: diazepam 2 mg orally three times daily for up to 5 days; avoid in older adults, with sleep apnoea, and with other sedatives.
• Oral prednisolone 30 to 40 mg once daily for 5 to 7 days gives a small short term benefit in some patients, with adverse effects such as insomnia, mood change and hyperglycaemia; use with caution, and avoid in diabetes and active infection.
• Epidural steroid injection (transforaminal dexamethasone 8 to 10 mg, non-particulate, or interlaminar methylprednisolone 40 mg) under image direction gives pain relief for 2 to 6 weeks and does not change the long term need for surgery.
• Limit epidural injections to no more than 3 in 12 months and at least 2 to 4 weeks apart; avoid with infection, uncontrolled diabetes, and unheld anticoagulants (hold apixaban or rivaroxaban for 72 hours and warfarin for 5 days with INR under 1.5).

Surgery.

• Emergency decompression for cauda equina syndrome (ideally within 24 to 48 hours of symptom onset, before retention is complete, for the best bladder recovery).
• Urgent surgery for progressive or severe motor deficit (power grade 3 or less, foot drop).
• Elective microdiscectomy for severe radicular pain persisting after 6 to 12 weeks of non-operative treatment, or recurrent disabling attacks; leg pain relief in 80 to 90%, faster than with non-operative treatment, with similar results after 2 to 4 years.
• Alternatives: endoscopic discectomy and tubular microdiscectomy. Complications: dural tear 1 to 3%, recurrent herniation 5 to 15%, infection about 1%, wrong level surgery, nerve injury about 1%, and persistent back pain.

Operative antibiotic prophylaxis. Cefazolin 2 g intravenously (3 g when weight is 120 kg or over) within 60 minutes before incision as a single dose (repeat after 4 hours or blood loss over 1500 mL). With severe penicillin allergy, vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose.

Thromboprophylaxis. Early mobilisation and mechanical measures; enoxaparin 40 mg subcutaneously once daily for 7 to 14 days (started 24 to 48 hours after surgery) only for patients at high risk (20 mg once daily at creatinine clearance under 30 mL/min).

Analgesia after surgery. Paracetamol 1 g orally every 6 hours; ibuprofen 400 mg orally every 8 hours with food for up to 5 days (maximum 1200 mg daily) in patients without contraindications; oral morphine 5 to 10 mg every 4 hours as needed for up to 3 days.

Monitoring. Review at 2 to 6 weeks for pain, neurology and bladder function; at 6 to 12 weeks decide on imaging and surgical referral. After surgery, review at 2 weeks and 6 weeks, with return to normal activity as pain allows. Watch for recurrent herniation (new pain after a pain free interval).

Referral and escalation. Refer to a spinal surgeon for pain persisting at 6 to 12 weeks, progressive weakness, or disabling pain. Emergency referral and MRI for suspected cauda equina syndrome.

Special groups.

• Pregnancy: non-operative management; MRI without gadolinium; surgery only for cauda equina syndrome or severe deficit; avoid NSAIDs in the third trimester and avoid gabapentinoids unless needed.
• Adolescents: consider an apophyseal ring fracture; surgery is more often needed.
• Older adults: stenosis often coexists; adjust analgesic doses for kidney function.
• Diabetes: caution with oral and epidural steroids; check glucose for 3 to 5 days.