Ischemic chiasmal syndrome.

Twenty-two patients with ischemic chiasmal syndrome (ICS) have been examined by means of magnification angiography and polytomographic encephalography. The causes of ICS may be divided into 5 categories: (1) mechanical compression of the chiasm by ectatic redundant anterior cerebral arteries, (2) atherosclerotic vascular occlusions, (3) optochiasmal arachnoidal fibrosis, (4) various forms of arteritis especially giant cell (cranial) arteritis, and (5) post-partum pituitary necrosis associated with ICS. The most common cause of ICS appears to be optochiasmal arachnoiditis which occasionally developed some time after a craniotomy and radiation therapy for pituitary or other juxta-sellar tumors; similar fibrotic change may develop following steroid treatment of granulomatous lesions.