Chronic pain syndromes and their treatment. III. The piriformis syndrome.

The piriformis is a deep-seated muscle, most of its muscular portion being part of the dorsal wall of the pelvis. The lateral portion and its insertion is extra-pelvic and lies deep to the glutei. Like more superficially located and therefore more easily accessible skeletal muscles, the piriformis too can be the seat of trigger points, giving rise to symptoms indistinguishable from those of other causes of low backache, unless a deliberate search is made for the signs specific to the piriformis syndrome. Having made a presumptive diagnosis, confirmation is gained by palpating the muscle itself via rectum or vagina and reproducing the pain by digital pressure. If this test also is positive, the muscle is injected, the approach being either through the sciatic notch, from the perineum, or through the vagina. Immediate relief of pain is experienced after the solution of local anaesthetic and steroid has been deposited deep within the fleshy portion of the muscle.