How to assess and manage sciatica?

Assessment of Sciatic Pain

Sciatica is diagnosed primarily through focused history and physical examination to identify pain radiating below the knee in the sciatic nerve distribution, with imaging reserved for specific clinical scenarios rather than routine evaluation. 1

Clinical History

Key historical features to elicit:

• Pain distribution: Pain must radiate down the leg below the knee into the foot and toes in the sciatic nerve distribution—this is the defining characteristic that distinguishes true sciatica from referred lower back pain 2, 3
• Duration and onset: Document whether symptoms are acute (<4 weeks), subacute (4-12 weeks), or chronic (>3 months) 1
• Aggravating factors: Pain typically worsens with sitting, standing, or specific movements 4
• Associated symptoms: Inquire about sensory changes, numbness, weakness, or diminished reflexes in the affected leg 2

Red flag symptoms requiring urgent evaluation:

• Urinary retention (90% sensitivity for cauda equina syndrome) 1
• Fecal incontinence or loss of sphincter control 1
• Saddle anesthesia (perianal or perineal numbness) 1
• Progressive bilateral motor weakness 1
• History of cancer, unexplained weight loss, fever, or failure to improve after 1 month 1

Physical Examination

Neurological assessment:

• Straight-leg-raise test: Flex the hip with knee extended; a positive test reproduces the patient's sciatica when the leg is raised between 30-70 degrees 1, 2
• Crossed straight-leg-raise test: Reproduction of sciatica when lifting the unaffected leg is highly specific for nerve root compression 1
• Motor examination: Test strength in specific nerve root distributions (L4: ankle dorsiflexion, L5: great toe extension, S1: ankle plantarflexion) 2
• Sensory examination: Assess for dermatomal sensory deficits, though dermatomes are unreliable and variable 2, 5
• Deep tendon reflexes: Check patellar (L4) and Achilles (S1) reflexes for diminution or absence 2

Provocative maneuvers:

• Flexion, adduction, and internal rotation (FAIR) test: Reproduces pain in piriformis syndrome, a non-discogenic cause of sciatica 4
• Freiberg sign and Pace sign: Additional tests for piriformis involvement 4
• Direct palpation: May identify mechanosensitized peripheral nerves in inflammatory states 5

Imaging Decisions

Imaging is NOT routinely indicated for initial assessment. 1

MRI lumbar spine without contrast is the preferred imaging modality when indicated: 1, 2

Specific indications for imaging:

• Persistent radicular symptoms after 6-8 weeks of conservative treatment in patients who are candidates for surgery or epidural steroid injection 1, 3
• Suspected cauda equina syndrome (urgent MRI required) 1
• Red flag symptoms suggesting malignancy, infection, or fracture 1
• Progressive neurologic deficits or multifocal deficits 1

Important caveats:

• Disc herniation is present in 20-28% of asymptomatic individuals, so imaging findings must correlate with clinical presentation 1
• The size and type of disc herniation do not predict patient outcomes 1
• Routine early imaging does not improve outcomes and increases costs 1

Diagnostic Classification

Categorize patients into one of three groups: 1

1. Nonspecific low back pain (85% of cases): Pain without radicular features or red flags 1
2. Back pain with radiculopathy or spinal stenosis: Sciatica or pseudoclaudication present 1
3. Back pain with specific spinal cause: Red flag conditions requiring urgent evaluation 1

Differential Diagnosis Considerations

Non-discogenic causes of sciatica to consider:

• Piriformis syndrome: Sciatica with buttocks pain, worse with sitting, normal neurological exam, negative straight-leg-raise, positive FAIR test 4
• Spinal stenosis: Neurogenic claudication with leg pain on walking/standing, relieved by sitting or spinal flexion 1
• Lumbosacral plexopathy: Clinical overlap with radiculopathy; may require MRI lumbosacral plexus if diagnosis unclear 1

Natural History

Most sciatica improves spontaneously: The clinical course is generally favorable, with most pain and disability improving within 2-4 weeks with or without treatment, and certainly by 4 weeks in the majority of cases 3, 6. This information should be communicated to patients during initial assessment 1.