超高齢者の歯突起後方偽腫瘍の1例

A Case of Retro-Odontoid Pseudotumor in a Very Elderly Individual

Ⅰ．はじめに

　歯突起後方偽腫瘍は，加齢性変化や関節リウマチなどによる環軸椎亜脱臼による力学的負荷の増大が原因とされている．神経症候の程度により手術適応が考慮されるが，高齢発症が多いため耐術能の問題がある．また術式に関しても，除圧術単独または固定術併用などさまざまな報告があり，議論の余地がある．今回われわれは，超高齢者の歯突起後方偽腫瘍に対して椎弓切除術のみを行い，良好な結果を得た症例を報告する．

　Retro-odontoid pseudotumors are mainly caused by aging or rheumatoid arthritis. We treated a very elderly patient with retro-odontoid pseudotumor. A 92-year-old man was admitted with the chief complaints of difficulty walking and progressive numbness in the right upper and lower extremities. Neurological examination revealed muscle weakness and exaggerated tendon reflexes of the right upper and lower extremities, and disturbance in skilled motor activities of the fingers, bilaterally. He had no bladder or rectal disturbances. The Japanese Orthopaedic Association（JOA）score for cervical myelopathy was 10/17. Rheumatoid arthritis was interpreted as negative. Radiography of the neck showed no atlanto-axial instability. Cervical magnetic resonance（MR）imaging revealed a mass located posterior to the C2 odontoid process, severely compressing the cervical cord. The patient underwent a C1 laminectomy and C2 half laminectomy without fixation to achieve cord decompression. Postoperatively, muscle weakness in the right upper and lower extremities was remarkably improved, and gait disturbance was also improved. However, skilled motor activities of the fingers on the right hand during tasks such as writing letters, holding a cup, and using chopsticks, were not improved. JOA score was improved to 14/17. Postoperative radiography revealed no atlanto-axial instability and MR imaging revealed adequate decompression of the spinal canal. Laminectomy without fixation is recommended as an effective and less invasive treatment for retro-odontoid pseudotumor, especially in very elderly patients without atlanto-axial instability.