What is pyriformis syndrome?

Piriformis Syndrome

Piriformis syndrome is a neuromuscular condition characterized by compression of the sciatic nerve by the piriformis muscle, causing buttock pain that radiates down the posterior aspect of the affected lower limb, often mimicking sciatica. 1

Clinical Presentation

• Primary symptoms:

  • Buttock pain (most common)
  • Sciatica-like pain radiating down the posterior thigh, leg, and foot
  • Pain worsens with sitting 2
  • External tenderness over the greater sciatic notch 3

• Physical examination findings:

  • Pain with flexion, adduction, and internal rotation of the hip
  • Positive Freiberg sign (pain with passive internal rotation of the extended thigh)
  • Positive Pace sign (pain with resisted abduction and external rotation)
  • Pain with direct palpation of the piriformis muscle 4
  • Normal neurological examination in most cases
  • Negative straight leg raising test (differentiating from disc herniation) 4

Pathophysiology

The piriformis muscle originates from the anterior surface of the sacrum, passes through the greater sciatic notch, and inserts on the greater trochanter of the femur. In approximately 16% of individuals, the sciatic nerve pierces through the piriformis muscle rather than passing beneath it, potentially predisposing these individuals to nerve compression 3.

Compression or irritation of the sciatic nerve can occur due to:

• Muscle hypertrophy
• Muscle spasm
• Anatomical variations
• Trauma to the buttock region
• Prolonged sitting or activities that strain the piriformis 2

Interestingly, posterior thigh pain in piriformis syndrome may involve the posterior femoral cutaneous nerve, possibly due to compression of the inferior gluteal vein by a hypertrophied piriformis muscle 5.

Diagnosis

Piriformis syndrome is primarily a clinical diagnosis of exclusion. Diagnostic challenges arise because:

1. No definitive diagnostic test exists
2. Symptoms overlap with other conditions like lumbar radiculopathy
3. Imaging studies are typically normal 4

Diagnostic approach:

• Rule out other causes of sciatica, particularly lumbar disc herniation
• Electrodiagnostic studies may be normal but help exclude other causes
• Imaging (MRI, ultrasound) primarily to rule out other pathologies
• Ultrasound may show thickening of the piriformis muscle in some cases 3
• Diagnostic piriformis muscle injections may provide temporary relief confirming the diagnosis

Treatment

Treatment follows a stepwise approach:

1. Conservative management (first-line treatment for at least 3 months):

   • Activity modification
   • Anti-inflammatory medications
   • Physical therapy focusing on piriformis stretching and strengthening
   • Local steroid injections into the piriformis muscle
   • Extracorporeal shock wave therapy 6

2. Interventional treatments for refractory cases:

   • Botulinum toxin injections into the piriformis muscle (effective for cases not responding to standard therapies) 2
   • Ultrasound guidance improves accuracy of injections 4

3. Surgical intervention for persistent cases:

   • Piriformis muscle resection with or without neurolysis of the sciatic nerve
   • Reserved for patients with intractable symptoms despite at least 3 months of conservative treatment
   • Studies show approximately 83% of properly selected patients achieve satisfactory results after surgery 6

Clinical Pearls and Pitfalls

• Buttock pain tends to respond better to conservative treatment than sciatica symptoms 6
• Piriformis syndrome accounts for approximately 5-6% of cases of low back, buttock, and leg pain 3
• The condition is often misdiagnosed as lumbar disc herniation or other causes of sciatica
• Patients typically have normal neurological examinations and negative straight leg raising tests, unlike those with disc herniation 4
• Proper patient selection is critical for successful surgical outcomes

Piriformis syndrome remains a challenging diagnosis requiring careful clinical evaluation to differentiate it from other causes of sciatica, but with appropriate treatment, most patients can achieve significant symptom relief.