Sciatica: Nerve Anatomy, Causes, Symptoms, and Treatment

Sciatic Nerve Anatomy

• Largest nerve (L4–S3 roots via lumbosacral plexus)
• Exits pelvis via greater sciatic foramen (infrapiriformis)
• Divides at popliteal fossa → tibial + common fibular nerves
• Innervates: posterior thigh (hamstrings), all leg/foot muscles, sensation posterior leg/lateral foot/sole

Sciatica = Radiculopathy (Usually L5/S1)

Compression/irritation of nerve root(s), not the peripheral nerve itself (except piriformis syndrome).

Common Etiologies

• Herniated nucleus pulposus (90%): Posterolateral disc → root compression
• Spinal stenosis: Central/foraminal narrowing (ligamentum flavum, facets)
• Spondylolisthesis: Vertebral slippage → foraminal stenosis
• Piriformis syndrome: Sciatic nerve compression at piriformis (15% anatomic variant: nerve through muscle)
• Trauma, tumor, infection, hematoma

Clinical Features

• Radiating pain: buttock → posterior thigh → leg/foot (dermatomal)
• Paresthesia, numbness in distribution
• Weakness: foot drop (L5), weak plantar flexion (S1)
• Positive straight leg raise (SLR) <60°; crossed SLR specific
• Reflex changes: absent ankle jerk (S1)

Treatment Algorithm

1. Conservative (6–12 wks): NSAIDs, activity modification (avoid bed rest), PT (McKenzie, core), neuropathic agents (gabapentin/pregabalin if needed)
2. Epidural steroid injection: Transforaminal > interlaminar; short-term benefit
3. Surgery (microdiscectomy/laminectomy): Progressive deficit, cauda equina, refractory pain >6–12 wks
4. Piriformis: PT, ultrasound-guided injection, rare surgical release

Prevention

• Core strengthening, hip mobility
• Proper lifting (hip hinge)
• Ergonomic sitting, frequent position changes
• Weight management