同名性視野欠損の性状と病巣局在との相関関係

CORRELATION BETWEEN HOMONYMOUS VISUAL FIELD DEFECTS AND LOCALIZATION OF INTRACRANIAL LESIONS

I．はじめに

　視覚路は，頭蓋内で長い径路をとりいろいろな部位で損傷を受け易く，また視覚路のどの部分が侵されるかによつてかなり特有の視野欠損を来し得るために，視野測定は頭蓋内病巣の局在診断上有意義な検査法となつている。しかしながら視覚路の詳細についてはいまだ不明の点があり，また実際に得られた視野表は種々の程度に修飾されているので，これのみから病巣の局在を決定するのは容易でないことがしばしばである。そこでわれわれはPostchiasmalの病巣によると考えられる同名性視野欠損を呈した59症例を選び出し，視野欠損の性状がどの程度病巣の局在診断に役立ち得るかを検討した。

Diagnostic value of homonymous visual field defects was estimated in 59 cases with intracranial lesions, such as 33 tumors, 15 vascular lesions, 4 injuries, 2 hydrocephalus, 3 abscesses, and 2 of un-known cause.

Congruous field defects were found in 17 cases (47%) out of 36 with space-taking lesions (tumor and abscess) and in 13 cases (87%) of 15 with vascular lesions. Visual field defects associated with space-taking lesions in the frontal base, close to the optic tract, or in the anterior part of the temporal lobe had a tendency to be incongruous. Regardless of congruity or incongruity of field defects, upper quadrantic or less than quadrantic field defects were recognized in the temporal space-taking lesions and lower quadrantic or less than quadrantic defects were found in the parietal lesions. Although "sparing of the macula" was able to be seen in field defects due to space-taking lesions locating in any portion along the postchiasmal visual pathway, it was relatively uncommon in the temporal lobe involvement. Homonymous chro-matoanopsia, which preceded loss of field for white, was found in 4 cases out of 47 examined with Förster's perimeter.

Theories or hypotheses about the post-chiasmal visual pathways and cortical center were summa-rized, and the field defects due to their involve-ments were discussed.

Homonymous visual field defects have somewhat limited value in topical diagnosis of intracranial lesions. Probably this limitation is mainly due to incomplete knowledge of topographic anatomy of the afferent visual projections at present time.