腰椎正中部に発生したSynovial Cystの1例

A Case of a Lumbar Spinal Synovial Cyst Located on the Midline

I．はじめに

　脊椎のsynovial cystは比較的稀な疾患であり，通常は椎間関節より発生するため，脊椎管背外側に位置することが多い^2,5）．今回われわれは，脊椎管背側正中部に発生したsynovial cystの1例を経験したので若干の文献的考察を考加えて報告する．

We report a case of lumbar spinal synovial cyst located on the midline. A 72-year-old man was admittedto our hospital with the chief complaint of low back pain radiating to the left buttock and posterior thigh.An MR image revealed an extradural cystic lesion adjacent to the dorsal side of the dural sac at the L4-5level. The cyst was remote from the facet joints and existed on the midline just in front of the L4 lamina.A CT scan showed a concave deformity of the ventral aspect of the L4 lamina because of compression bythe cyst. The patient underwent L4 laminectomy and total removal of the cyst. The cyst was in contactwith the anterior surface of the ligamentum flavum and it had no connection with the facet joint. In thehistological examination, the cyst was multilobular and lined with synovial epithelium. Therefore the cystwas diagnosed as a synovial cyst. After the operation, the pain radiating to the buttock and thigh com-pletely disappeared.

Intraspinal synovial cysts are usually located in the lower lumbar spine and most of them are adjacent tothe facet joint. The cysts that are located on the midline are very rare. We review previous reports and dis-cuss clinical and pathological features of spinal synovial cysts.