Dr Harith Rosdi
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Piriformis Syndrome

Definition

Non-discogenic entrapment of the sciatic nerve by the piriformis muscle in the buttock.

Epidemiology

  • More common in women
  • Typical age: 30 to 50 years
  • Risk settings: prolonged sitting (drivers, desk workers, “wallet sciatica”), direct buttock trauma, runners and cyclists with hip muscle imbalance

Relevant Anatomy

  • Sciatic nerve passes ANTERIOR to Piriformis and exits inferior to piriformis and superior to superior gemellus
  • Muscles: external rotators of the thigh include (superior to inferior)
    • Piriformis
    • Superior gemellus
    • Obturator internus
    • Inferior gemellus
    • Obturator externus
    • Quadratus femoris
Posterior view of the pelvis and hip showing the piriformis muscle, the sciatic notch, the superior and inferior gemelli and obturator internus, and the sciatic nerve passing beneath the piriformis

Pathophysiology and Causes

Sciatic nerve compression in the deep gluteal space

Piriformis-related

  • Hypertrophy, spasm or contracture
  • Post-traumatic scarring after a fall onto the buttock
  • Anatomical variants: bipartite muscle, nerve piercing the muscle

Other causes

  • Space-occupying lesions: tumour, haematoma, abscess

Clinical Presentation

History

  • Buttock pain, often deep and unilateral
  • Radiation down the posterior thigh, sometimes below the knee
  • Neuropathic: burning, shooting, tingling
  • Unable to sit for more than about 30 minutes. Classic
  • Worse with climbing stairs
  • Possible numbness and weakness in the sciatic distribution
  • Usually little or no low back pain

Examination

  • Deep gluteal tenderness over piriformis
  • Provacative tests: FAIR / Seated piriformis stretch test
  • Straight leg raise often normal
  • Neurological exam usually normal; check to exclude radiculopathy
The FAIR test: a supine patient’s hip is flexed, adducted and internally rotated while the pelvis is stabilised, with an arrow marking the region of buttock pain the position provokes
The seated piriformis stretch test: a seated patient’s leg is taken into flexion, adduction and internal rotation while the examiner palpates the deep gluteal region

Investigations

Piriformis syndrome is largely a diagnosis of exclusion.

  • Lumbar spine MRI: exclude disc herniation, foraminal or spinal stenosis
  • Ultrasound: dynamic assessment of sciatic nerve and piriformis; guides injections

Management

Non-operative (first line & most patients improve)

  • Education and activity modification: reduce prolonged sitting, avoid sitting on a wallet, use cushions and regular breaks

Physiotherapy

  • Stretching of piriformis and short external rotators
  • Hip muscles strengthening, core stability
  • Sciatic nerve gliding/mobilisation
  • Soft tissue manipulation
  • Modalities such as TECAR therapy
  • Medications: NSAIDs, muscle relaxants (such as Myonal), neuropathic agents (such as Gabapentin, Pregabalin) for neuropathic pain
  • Image-guided injections (ultrasound)
  • Local anaesthetic ± corticosteroid into piriformis or perineural around the sciatic nerve
  • Both diagnostic and therapeutic
  • Botulinum toxin for refractory cases

References

  1. Martin, H. D., Reddy, M., & Gomez-Hoyos, J. (2015). Deep gluteal syndrome. Journal of Hip Preservation Surgery, 2(2), 99-107. doi:10.1093/jhps/hnv029
  2. Robinson, D. R. (1947). Pyriformis syndrome in relation to sciatic pain. The American Journal of Surgery, 73(3), 355-358

Medical disclaimer: this article is general information, not personal medical advice. Always consult a qualified doctor about your own situation.