特発性胸髄脊髄ヘルニアの1例

A Case of Idiopathic Thoracic Spinal Cord Herniation

　要旨　今回われわれは胸髄に発生した特発性脊髄ヘルニアの症例を経験したので報告する。症例は63歳女性，5年前から徐々に進行する歩行障害を主訴に来院した。左下肢優位の両下肢筋力低下と感覚障害を認め，すでに左下垂足になっていた。MRI，ミエロCTではT2-3レベルで脊髄の腹側偏位と萎縮，背側のクモ膜下腔拡大を認めた。画像所見から特発性脊髄ヘルニアを疑い手術を施行した。T2-3椎弓切除し，硬膜切開した後に脊髄腹側を観察すると，硬膜の2重構造とその内層に欠損を認め，そこに脊髄が嵌頓していた。ヘルニア孔から脊髄を解除し，硬膜欠損部を人工硬膜にて硬膜形成した。術後の右下肢筋力低下は改善したが，左下肢の症状改善は軽度だった。本症の症状は緩徐に進行し，放置した場合は対麻痺に至るので，早期発見と手術治療が症状の進行防止および改善に重要であると思われた。

　We report a case of idiopathic thoracic spinal cord herniation. A 63-year-old female came to our hospital complaining of a slowly progressive gait disturbance that began 5 years ago. She showed signs of a left dominant spastic paraparesis and sensory disturbance. Her left foot had already became a drop foot from 2 years ago. Magnetic resonance（MR） imaging and computed tomographic（CT） myelography demonstrated that the atrophic spinal cord had displaced to the ventral side with a dilated dorsal subarachnoid space at T2-3 level. Surgery was performed via T2-3 laminoplastic laminectomy. The ventral aspect of the spinal cord revealed a defect in the inner layer of the duplicated dura mater, into which the gliotic spinal cord herniated. The herniated spinal cord was repositioned and the dural defect was repaired using a GORE-TEX^(R) dura substitute. Postoperative course was uneventful. Although the patient showed marked improvement in the right lower limb, there was slight improvement in the left lower limb. The clinical symptoms of this disease are uncommon and progress slowly, and if left untreated will result in paraparesis. Therefore early diagnosis and operation is important to prevent the progression of symptoms and to achieve a satisfactory outcome.