椎間板ヘルニアと同一高位に生じた馬尾神経鞘腫の1例

Cauda Equina Tumor Associated with Herniated Lumbar Disc at the Same Level : Case Report

　抄録：同一高位に椎間板ヘルニアを合併した馬尾腫瘍の1例を経験し報告した．症例は41歳，男性で主訴は腰痛，両下肢筋力低下である．MRIにてL4/5の椎間板ヘルニアとL4椎体高位の硬膜内にT1強調画像にて椎間板と等信号強度，T2強調画像にて高信号強度，Gdにて不均一に造影される不定形な腫瘤像を認めた．腫瘤の鑑別疾患として硬膜内脱出ヘルニアあるいは馬尾腫瘍が疑われた．手術は後方除圧術と腫瘤摘出術を施行した．腫瘤は馬尾腫瘍であり，病理所見は神経鞘腫であったが，術中所見として全周性のくも膜炎，腫瘍被膜の著明な肥厚，馬尾の癒着を認めた．本例は，下肢痛を伴わない両下肢筋力低下および術中所見から馬尾腫瘍が主病態と考えられたが，急性腰痛での発症には，椎間板ヘルニアが影響したものと推察された．

　We report a case of cauda equina tumor associated with herniated lumbar disc at the same spinal level. A 41-year-old man presented with a 3-month history of low back pain and motor weakness of the lower extremities. Magnetic resonance imaging revealed a herniated lumbar disc at the L4-L5 level and an irregularly shaped tumor. The tumor was isointense with the disc on the T1-weighted image and heterogeneously enhanced with gadolinium, and it was high intensity on the T2-weighted image. Before surgery we suspected intradural disc herniation or a cauda equina tumor, and during surgery we found a cauda equina tumor encapsulated by thick connective tissue associated with severe arachnoiditis. Histologic examination of the specimen revealed a neurinoma. In view of the history and surgical findings in this case, the herniated lumbar disc induced acute symptoms associated with a cauda equina tumor that had been asymptomatic for a long time.