Expanding supratentorial lesions, regardless of location, can cause ischemic or hemorrhagic infarction of one or both occipital lobes by compression of the posterior cerebral arteries against the tentorium. Compression of the posterior cerebral artery and resultant infarction of the visual cortex are frequently observed by the neuropathologist. Such infarctions occur secondary to herniation of the brain through the tentorial incisura. Herniations in turn are the direct result of increased supratentorial pressure.
The clinical correlation of some of the ophthalmologic signs occurring with transtentorial herniation of the brain (such as pupillary and oculomotor signs) has been described in great detail.1,2 However, compression of branches of the posterior cerebral arteries as a cause of homonymous hemianopsia and visual agnosia in patients with increasing intracranial pressure has seldom been mentioned in the ophthalmologic literature. (Lyle,3 Huber,4 and Walsh5 discussed the general problem but presented no clinical material.)
HOYT WF. Vascular Lesions of the Visual Cortex with Brain Herniation Through the Tentorial IncisuraNeuro-Ophthalmologic Considerations. AMA Arch Ophthalmol. 1960;64(1):44-57. doi:10.1001/archopht.1960.01840010046003