Piriformis syndrome is a rare, predominantly clinical diagnosis in which the piriformis muscle compresses or irritates the sciatic nerve. From a neurosurgical perspective, it is an extraspinal compression syndrome of the sciatic nerve and therefore an important differential diagnosis in patients with radicular leg symptoms without correlating findings in the lumbar spine.
Epidemiology
According to estimates, approximately 0.3–6 % of all patients with “sciatica symptoms” have piriformis syndrome. It more commonly affects physically active individuals and patients with anatomical variants of the sciatic nerve (e.g., passage through the piriformis muscle).
Etiology
Common causes of piriformis syndrome include:
Hypertrophy or tension of the piriformis muscle, for example due to overuse, trauma, or abnormal loading.
Post-traumatic changes after a fall or direct trauma to the buttock
Anatomical variants (e.g., split sciatic nerve fascicles)
Diagnostic workup
It is primarily a clinical diagnosis of exclusion. The following clinical tests may be helpful in diagnosing piriformis syndrome:
FAIR test (flexion, adduction, internal rotation)
Freiberg maneuver
Pace test
Beatty maneuver
Treatment
The gold standard for treating piriformis syndrome is conservative treatment consisting of:
Stretching and strengthening exercises as part of physical therapy
Pharmacologic pain therapy, for example with NSAIDs
CT- or ultrasound-guided injection of the piriformis muscle[^1]
Prognosis
The prognosis is good with a correct diagnosis. The majority of patients achieve significant symptom relief with conservative treatment.