聴神経腫瘍根治術における脳神経の保存とその機能的予後

Functional Results of Preservation of Cranial Nerves in Removal of Acoustic Neurinoma

I．はじめに

　聴神経腫瘍の手術成績は高分解能computed tomo—graphy（CT）や磁気共鳴画像（MRI）による画像診断法の進歩と顕微鏡手術の普及によって著しく改善され，手術による死亡は姿を消し，高い頻度での顔面神経の保存2，^8,13），また小型の腫瘍では聴力の保存が得られると報告されるようになってきている^10,12）．しかしこれら保存を試みられた神経機能の長期的観察結果についての詳細な記載は見当らない．

　本報告では最近6年間の手術例について顔面神経，聴神経機能が実際にどの程度の機能の保存が可能であったかという点について検討した．

Seventeen patients with acoustic neurinoma were re-viewed on the basis of postoperative preservation of fa-cial and acoustic nerve functions. The sizes of tumors were intracanalicular in 5 cases, smaller than 20mm in diameter in 2 cases, smaller than 30mm in 5 cases, and larger than 30mm in 5 cases.

In all cases, the facial nerve was anatomically pre-served at operation. Functional recoveries of the facial nerve in follow-up were excellent in 7 cases out of 17 (41%), good in 5 (29%) and poor in 5 (29%). Although the functional preservation for the facial nerve was re-lated to the size of the tumor, it was favorable in cases of cystic tumor even with a size larger than 20mm. By pure tone audiogram, hearing was found to be preserved in 12 cases before operation. At operation, the acoustic nerve was anatomically preserved in 4 cases. Postoperative hearing was maintained in two cases, one of which showed a successful preservation of serviceable hearing. In this case, tumor resection was performed with intraoperative monitoring of auditory brain stem reactions (ABRs).

Discussion was made concerning a possible surgical candidates for the hearing preservation, and it wasproposed that every effort should be made to preserve the cochlear nerve if following conditions were verified in the case: 1) normal or nearly normal hearing (less than 90 - 50dB hearing loss), 2) the size of tumor is in-tracanalicular or smaller than 2cm in diameter, 3) there is no deterioration of intraoperative ABR.