Review Question - QID 216988

This patient presents with left posterior gluteal and thigh pain of a burning quality that radiates down his leg reminiscent of sciatica with a positive FAIR (Flexion, Adduction, Internal Rotation of the hip) test, indicative of piriformis syndrome. Piriformis syndrome is caused by entrapment of the sciatic nerve at the piriformis muscle.

The sciatic nerve exits the greater sciatic notch inferior to the piriformis muscle and runs posterior to the short external rotators of the hip (superior gemellus, obturator internus, inferior gemellus, quadratus femoris). Entrapment can occur anterior to the piriformis or posterior to the obturator internus-gemelli complex. Hip flexion, adduction, and internal rotation (i.e., the FAIR test) puts the piriformis muscle under tension, aggravating the symptoms. The test is considered positive when sciatic/gluteal pain is elicited. Work-up can include radiographs and MRI, which are usually unremarkable but can rule out other causes of pain including disease in the lumbar spine. Treatment is with rest, non-steroidal anti-inflammatory drugs, and physical therapy. Surgery to release the piriformis muscle and decompress the sciatic nerve is indicated in refractory cases.

Kirschner et al. review the diagnosis and treatment of piriformis syndrome. They outline the emergence of botulinum toxin as a potential treatment modality for this condition.

Incorrect Answers:
Answer 1: Compression of nerve roots in the lumbar spine describes cauda equina syndrome, which is a surgical emergency that presents with saddle anesthesia, urinary/bowel incontinence, and low back/leg pain. This patient lacks saddle anesthesia or incontinence.

Answer 2: Malignant growth of mesenchymal cells describes a soft tissue sarcoma, which could exert a mass effect on the sciatic nerve, causing posterior thigh pain. However, patients with malignancy typically present with constitutional symptoms such as unintentional weight loss, fatigue, and night pain. Additionally, the FAIR test would not be expected to be positive.

Answer 4: Overuse of the hamstring muscles describes a hamstring strain, which can present as posterior thigh pain but is usually described as a sharp, sudden pain that may be accompanied by a popping sensation during injury. This patient’s burning pain is more consistent with a nerve etiology, and the positive FAIR test implicates the piriformis as the likely site of pathology.

Answer 5: Protrusion of the nucleus pulposus through the annulus fibrosus describes a herniated disc, which can present with sciatic nerve symptoms as well when it occurs in the lumbar spine. However, the straight leg raise (hip flexion with the knee extended) test would reproduce the pain as this causes impingement on the affected nerve root.

Bullet Summary:
Piriformis syndrome is caused by sciatic nerve entrapment anterior to the piriformis muscle or posterior to the obturator internus-gemelli complex.