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Emergency and Acute Medicine – Sciatica / Herniated Disc
Sciatica, most commonly caused by a herniated lumbar disc, refers to radicular pain radiating from the lower back into the buttock and down the leg (typically below the knee). It is highly suggestive of nerve root compression, with about 95% of cases involving the L5 or S1 nerve roots. The condition has a 3–5% lifetime prevalence, most commonly affecting individuals in their 40s to 50s, and accounts for a subset of low back pain presentations. Fortunately, ~90% of patients improve with conservative treatment, and symptoms usually resolve within 6 weeks, though a small percentage require surgery.
The underlying mechanism involves herniation of the nucleus pulposus through the annulus fibrosus, leading to compression and inflammation of adjacent nerve roots. Common risk factors include smoking, obesity, repetitive lifting or twisting, prolonged vibration exposure (e.g., driving machinery), and sedentary lifestyle. Symptoms often begin with low back pain, followed by progressively dominant leg pain that is sharp, well localized, and radiates distally.
Patients typically report worsening pain with activities that increase intradiscal pressure, such as coughing, sneezing, or straining (Valsalva maneuver), as well as prolonged sitting or leg elevation. Pain is often relieved by lying supine or walking. The most common sensory symptom is paresthesia. On examination, a detailed neurologic assessment is essential. Findings depend on the affected nerve root:
- L4 (L3–L4 disc): Knee extension weakness, reduced patellar reflex, sensory loss over medial leg
- L5 (L4–L5 disc): Weakness in great toe dorsiflexion, sensory loss in 1st web space
- S1 (L5–S1 disc): Weak plantarflexion, reduced Achilles reflex, sensory loss over lateral foot
The straight leg raise (SLR) test is a key bedside maneuver—raising the affected leg to 30–60° reproducing radicular pain is highly sensitive. A crossed SLR test (pain in the affected leg when lifting the opposite leg) is less sensitive but highly specific.
Diagnosis is primarily clinical. Imaging is not routinely required unless red flags are present (e.g., trauma, fever, cancer history, severe or progressive neurologic deficits). MRI is the gold standard when indicated—especially in cases of suspected infection, severe deficits, or failure of conservative therapy after 6 weeks. Importantly, imaging findings must be correlated clinically, as many asymptomatic individuals have disc abnormalities.
Emergency management focuses on excluding neurosurgical emergencies, particularly cauda equina syndrome (e.g., urinary retention, saddle anesthesia, decreased rectal tone). In uncomplicated cases, treatment is conservative, including:
- NSAIDs (first-line) for pain relief
- Short-term use of muscle relaxants or opioids if needed
- Early mobilization (avoid prolonged bed rest—max 1–2 days)
Patients should be advised to gradually resume activity while avoiding heavy lifting, bending, twisting, and vibration exposure.
Admission is required for severe or progressive neurologic deficits, inability to ambulate, suspected infection, malignancy, or cauda equina syndrome. Most patients can be safely discharged with follow-up within 1 week and a plan for conservative therapy over 4–6 weeks.
A critical clinical pearl is to always assess for red flags and neurologic deficits, as missing serious causes (e.g., epidural abscess or cauda equina syndrome) can lead to permanent disability. Conversely, overuse of imaging should be avoided in uncomplicated cases, as most patients improve without intervention.
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