Sciatica

Overview

Sciatica is a condition characterised by pain that radiates from the lower back down into the leg, following the pathway of the sciatic nerve. The pain can be sharp, shooting, and may be accompanied by numbness or weakness in the affected leg. The onset can be sudden, often associated with activities such as heavy lifting, but it can also develop gradually.

Signs & Symptoms

Typical symptoms of sciatica include:

• Pain radiating from the lower back down the leg.
• Pain that may be described as shooting or shock-like.
• Weakness or numbness in the affected leg and foot.
• Lower back pain can also be present.
• Symptoms usually occur on one side of the body but can affect both sides in certain conditions.

Complications may include loss of bowel or bladder control, which requires immediate medical attention.

Causes

Risk Factors

Modifiable risk factors for sciatica include smoking, obesity, occupation, and physical sports involving back muscles and heavy weights. Non-modifiable risk factors include increasing age, being male, and a personal history of low back pain.

Common Causes

1. Spinal Disc Herniation: The most common cause, present in about 90% of cases, especially in individuals under age 50.
2. Spinal Stenosis: More frequent in those over 50, caused by narrowing of the spinal canal.
3. Piriformis Syndrome: Compression of the sciatic nerve by the piriformis muscle, contributing to 8% of low back or buttock pain cases.
4. Deep Gluteal Syndrome: Includes multiple causes of sciatic nerve entrapment in the deep gluteal space, such as fibrous bands and vascular abnormalities.
5. Other Causes: Include endometriosis, pregnancy, trauma, and tumours impinging on the sciatic nerve.

Pathophysiology

Intraspinal Sciatica

Sciatica can occur due to spinal issues such as herniated discs pressing on the lumbar or sacral nerve roots. This usually involves the L4, L5, S1, S2, and S3 nerve roots merging to form the sciatic nerve.

Extraspinal Sciatica

This involves entrapment of the sciatic nerve outside the spine, such as in piriformis syndrome or deep gluteal syndrome. Pathologies like fibrovascular scar bands can restrict nerve mobility and cause pain.

Diagnosis

Sciatica is typically diagnosed through physical examination and patient history. The straight-leg-raising test is frequently used, and is considered positive if pain is reproduced with passive leg flexion.

Medical Imaging

CT or MRI can help diagnose lumbar disc herniation. Discography may be used to identify specific disc abnormalities.

Differential Diagnosis

Conditions such as cancer, spinal epidural abscess, proximal diabetic neuropathy, shingles, and acute Lyme radiculopathy should be considered. Symptoms like unexplained weight loss, fever, or unremitting pain may indicate these conditions.

Treatment

Physical Activity

Physical activity is often recommended for those able to perform it, although its effectiveness compared to bed rest is not fully clear. Physical therapy and nerve mobilisation techniques are commonly used.

Medication

NSAIDs are generally recommended as first-line treatment, though their effectiveness is limited. Opioids, muscle relaxants, and anticonvulsants have poor evidence of efficacy. Steroids may be used in confirmed disc herniation cases, and antidepressants may help in chronic sciatica.

Surgery

Surgery, such as discectomy, may be considered if conservative treatment fails or if there are severe symptoms like loss of bowel or bladder function. For non-discogenic sciatica, nerve decompression surgeries may be performed.

Alternative Medicine

Spinal manipulation may be effective for acute sciatica but has limited evidence for chronic cases. It is generally safe but contraindicated in cases of progressive neurological deficits.

Prognosis

Approximately 39% to 50% of people with sciatica still have symptoms after one to four years. Around 20% may be unable to work after one year, and 10% may require surgery.

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Self-assessment MCQs (single best answer)

What is the primary characteristic of sciatica?

Which of the following is a non-modifiable risk factor for sciatica?

What is the most common cause of sciatica, especially in individuals under age 50?

Which nerve roots are involved in the formation of the sciatic nerve?

Which test is commonly used to diagnose sciatica through physical examination?

Which imaging technique can help diagnose lumbar disc herniation?

Which of the following medications is generally recommended as the first-line treatment for sciatica?

What is the potential severe complication of sciatica that requires immediate medical attention?

Which syndrome involves the compression of the sciatic nerve by the piriformis muscle?

In cases where conservative treatment fails, what surgical procedure might be considered for sciatica?