シネMRIが術前診断に有用であった梨状筋症候群の2例

Diagnosis of Piriformis Syndrome by Cine MRI

　梨状筋症候群に対し術前診断にシネMRIを撮像した2例を経験したので報告する．シネMRIとは同一断面の画像を動画で経時的変化を観察する手法であり，梨状筋症候群に対する初めての動的画像診断法である．撮像シーケンスはfast imaging employing steady state acquisition(2D FIESTA)法を用い，股関節を外旋位から内旋位に動かしながら高速撮像し，最大内旋位で梨状筋による坐骨神経の圧迫を認めた．本法は梨状筋による坐骨神経に対する動的な圧迫を示し術前診断に有用であった．

　We report the cases of two patients with piriformis syndrome who complained of chronic pain in the buttock and thigh and in whom we used cine MRI to make the preoperative diagnosis.　Although the pain was relieved after a piriformis muscle block, conventional static MRI showed no evidence of sciatic nerve compression by the piriformis muscle.　Continuous cine MRI images were taken to look for evidence of dynamic compression as the patients moved their hip joint from external rotation to internal rotation.　The sequences were performed by fast imaging employing steady state acquisition (2D FIESTA).　In both cases, cine MRI revealed dynamic compression of the sciatic nerve by the piriformis muscle when in the internally rotated position, and the pain was relieved after piriformis muscle resection.　This is the first report on the use of cine MRI for the diagnosis of piriformis syndrome.　Cine MRI is valuable for identifying dynamic compression in piriformis syndrome cases.