歯突起後方偽腫瘍に対し顕微鏡視下に経硬膜的に腫瘤を摘出した1例

Transdural Resection of Retro-odontoid Pseudotumor Using a Microscope : A Case Report

　歯突起後方偽腫瘍により頚髄症を生じた1例を経験したので報告する．症例は74歳の男性で，主訴は歩行困難，両手巧緻運動障害であった．MRI上T1強調画像で等信号，T2強調画像で低信号を呈する腫瘤が歯突起後方で脊髄を圧迫していた．単純X線動態撮影で環軸関節に不安定性を認めなかったが，CT画像上，環椎後頭関節の左側に関節症性変化を認めた．環椎後弓切除後，顕微鏡下で経硬膜的に偽腫瘍を摘出した．術後1年の現在，偽腫瘍は縮小し症状は改善している．本症例では環椎後頭関節の関節症性変化を認め，歯突起後方偽腫瘍の発生要因の1つと考えられた．

　We report the case of a 74-year-old man with hand clumsiness and gait disturbance caused by a retro-odontoid pseudotumor.　Magnetic resonance imaging showed a retro-odontoid lesion.　This lesion showed isointensity on T1-weighted images and low intensity on T2-weighted images.　Dynamic roentogenogram with lateral views of the cervical spine substantiated no instability at the atlanto-axial joint, but CT revealed a degenerative change at the left atlanto-occipital joint.　Under the microscope, C1 laminectomy and transdural resection of the mass were performed.　At 1 year after the surgery, the size of the residual pseudotumor reduced, and the patient's symptom has improved.　Secondary osteoarthritis at the atlanto-axial joint could be one of the several mechanisms that produced the pseudotumor.