[A case of binasal quadrantanopsia due to opto-chiasmal arachnoiditis (author's transl)].

A case of binasal quadrantanopsia due to chiasmal arachnoiditis was reported. The patient was a 28-year-old man who complained of blurring of vision for 12 months. Visual acuity of the right eye was 20 cm/numerus digitorum and the left 0.7X contact lens. Visual field revealed binasal lower quadrantanopsia. Pneumoencephalogram showed poor filling in the chiasmatic cistern, but the angiogram and CT scan showed no parasellar mass lesion. Then optochiasmal arachnoiditis was diagnosed and a right frontal craniotomy was performed. The arachnoid around the post-fixed chiasm was thickened and adhered to the bilateral rectal gyri. Proximal parts of A--1 segments of bilateral anterior cerebral arteries were displaced medially and downward, compressing the both lateral aspects of the chiasm. Compression of the optic chiasm by the anterior cerebral arteries was relieved after removed of the arachnoid. Despite of the slight improvement of visual acuity, visual fields were not changed postoperatively. The authors briefly discussed the mechanism of binasal hemianopsia in our case and reviewed recent literatures.