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Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

Overview

• Piriformis syndrome is a condition in which the sciatic nerve becomes compressed or irritated by the piriformis muscle.
• It is an uncommon but important cause of sciatica.
• The condition may mimic symptoms of lumbar disc herniation or lumbar radiculopathy.
• It should be considered in patients with persistent buttock or leg pain when spinal causes are excluded.

Anatomical Basis

• The piriformis muscle lies in the gluteal region and passes from the sacrum to the greater trochanter of the femur.
• The sciatic nerve usually passes inferior to the piriformis muscle.
• Compression or irritation of the sciatic nerve in this region may lead to symptoms of piriformis syndrome.

Clinical Significance

• Compression of the sciatic nerve by the piriformis muscle may cause sciatica.
• Pain typically radiates from the buttock to the posterior thigh and sometimes to the leg.
• Symptoms may resemble those of lumbar disc herniation.

Common Symptoms

• Buttock pain.
• Pain aggravated by prolonged sitting or driving.
• Tenderness over the greater sciatic notch.
• Pain radiating down the posterior thigh or leg.
• Paresthesia or numbness in the distribution of the sciatic nerve.

Possible Causes

• Anatomical variations between the piriformis muscle and sciatic nerve.
• Muscle spasm or tightness of the piriformis muscle.
• Fibrous bands compressing the sciatic nerve.
• Vascular anomalies in the gluteal region.
• Blunt trauma to the buttock.

Differentiation from Lumbar Radiculopathy

• Lumbar radiculopathy is usually caused by compression of the nerve root at the spine, often due to disc herniation.
• Piriformis syndrome results from compression of the sciatic nerve outside the spine.
• MRI of the lumbar spine is often used to exclude spinal causes of sciatica.
• Diagnosis of piriformis syndrome is often made after excluding spinal pathology.

Diagnostic Evaluation

• Diagnosis is mainly clinical and based on patient history and physical examination.
• Pain is usually localized to the posterior gluteal region.
• Symptoms often worsen with sitting, running, or cycling.
• Palpation of the piriformis muscle region may reproduce pain.

Imaging

• MRI may occasionally demonstrate enlargement of the piriformis muscle.
• It may also reveal anatomical variations or sciatic nerve compression.
• However, imaging is primarily used to rule out other causes of sciatica.

Provocative Clinical Tests

• Stretching maneuvers that place tension on the piriformis muscle may reproduce symptoms.
• Flexion of the hip to approximately 90 degrees with the knee extended may provoke pain.
• The FAIR test involves flexion, adduction, and internal rotation of the hip to reproduce symptoms.

Diagnostic Injection

• Injection of local anesthetic into the piriformis muscle can help confirm the diagnosis.
• Relief of symptoms after injection supports the diagnosis of piriformis syndrome.

Treatment

• Initial management is usually conservative.
• Physical therapy and stretching exercises for the piriformis muscle.
• Nonsteroidal anti-inflammatory medications.
• Local steroid or anesthetic injections may be used for persistent symptoms.

Surgical Management

• Surgery is considered only when conservative treatments fail.
• The procedure may involve release of the piriformis muscle.
• Surgical decompression of the sciatic nerve may also be performed.