The traditional treatment of piriformis syndrome includes heat modality, deep muscle massage, slow stretch exercise, injection of local anesthetics, and surgical division of piriformis muscles in some selected cases. More recently, the use of botulinum toxin (BTX) for the treatment of piriformis syndrome has been suggested. We experienced two cases of piriformis syndrome with distinctive clinical feature. The symptoms of these two cases were not controlled by conservative managements including physical therapy, direct injection of lidocaine or steroid, or caudal block. So we injected Type A BTX in the piriformis muscle with the guidance of CT scan. 8 weeks after the botulinum injection, symptoms had almost completely disappeared, and follow up CT scan showed sufficient atrophy of piriformis muscles. The CT guided BTX injection in the piriformis muscle might emerge as a feasible technique to obtain a good local therapeutic effect without risk of imprecise inoculation. (J Korean Acad Rehab Med 2009; 33: 353- 356)
