小脳橋角部腫瘍における上小脳動脈の偏位の診断的意義

DISPLACEMENT OF THE SUPERIOR CEREBELLAR ARTERY IN THE DIAGNOSIS OF THE CEREBELLOPONTINE ANGLE TUMOR

I．緒言

　脳血管撮影の発達に伴い天幕上腫瘍の大部分のものは，頸動脈写によりその局在診断，腫瘍の大きさ，あるいは，腫瘍の病理組織まで推定することが可能であるが，椎骨動脈写による天幕下踵瘍の局在診断は，たとえば，hemangioblastomaやmeningiomaのある種のもののように血管性に富む腫瘍陰影のあるものはさておき，後頭蓋窩内を走る血管には，いわゆるnormal var—iationが多いため，血管の偏位や伸展の判定がむずかしく，正確な局在診断は困難な場合が多い^1）〜5）。

　また，手技のうえからも椎骨動脈写は頸動脈写ほど簡単ではなく，天幕下腫瘍の診断は主に，気脳写，ヨード脳室写が用いられていたが，近年ようやく椎骨動脈写に関する報告も多くなつてきた。

It is said that the first part of the superior cerebel-lar artery is displaced upward and medially in the cases of acoustic neurinoma. However, only few pa-pers have mentioned about the diagnostic value of this angiographic sign.

This report is based on an analysis of 64 cases of vertebral angiograms with special attention to the upward and medial displacement of the first part of the superior cerebellar artery. The films were careful-ly studied to clarify the following points :

1) Whether this displacement is pathognomonic to the angle tumor or not.

2) If so, how large is the size of the tumor neces-sary to show this displacement on the film.

3) How much diagnostic value this sign has in corn-parison with neurological signs in early stage of the angle tumors.

Of the 64 cases, 11 had cerebellopontine angle tu-mor, 7 of them were unilateral acoustic neurinomas, 2 were bilateral acoustic neurinomas, and 2 had glio-mas fairly well localized to the cerebellopontine an-gle region. 27 cases had tumors of other region in the posterior fossa, 6 cases had supratentorial lesions and 20 cases had non-space-taking lesions. By ex-amining all of these films, we found the upward and medial displacement of the superior cerebellar artery only in 9 cases of cerebellopontine angle tu-mors. All of these tumors which showed the dis-placement were proved to be larger than 2.5 cm in diameter at the time of operation : In other words, the tumors smaller than 2. 5 cm in diameter do not show the displacement of the superior cerebellar artery on the film.

As shown on the table, in comparison with neuro-logical signs, these tumors which were large enough to show this displacement, also showed neurological signs which were characteristic enough to make di-agnosis without other diagnostic aids.

The above mentioned results of the analysis lead to the following conclusions:

1) Upward and medial displacement of the first part of the superior cerebellar artery is pathognomonic to the cerebellopontine angle tumor.

2) This displacement describes more characteristic configuration in the half axial anteroposterior pro-jection than in the lateral projection. However, in making a definitive diagnosis, both views must be carefully examined.

3) This displacement is noted only when the size of the tumor is larger than 2. 5 cm in diameter. There-fore, vertebral angiography has little value in early diagnosis of the cerebellopontine angle tumor.

4) The size of the cerebellopontine angle tumor can be estimated to a certain extent by presence or ab-sence of this dislocation and by the degree of this dislocation.