In 17% of an assumed normal population the sciatic nerve passes through the piriformis muscle, rather than underneath it; however, in patients undergoing surgery for suspected piriformis syndrome such an anomaly was found only 16.2% of the time leading to doubt about the importance of the anomaly as a factor in piriformis syndrome. Some researchers discount the importance of this relationship in the etiology of the syndrome. MRI findings have shown that both hypertrophy (unusual largeness) and atrophy (unusual smallness) of the piriformis muscle correlate with the supposed condition.