• Hemiplegia, monoplegia, hemianesthesia, aphasia, and visual disturbances are all manifestations of sudden, transient focal cerebral vascular disturbances. Rhesus monkeys, whose pial vessels are similar to those of man, were studied to clarify the etiology of these transient cerebral strokes. The results of the experimental studies suggest it is unlikely that cerebral angiospasm can occur, but rather that the transient cerebral stroke is due to cerebral thrombosis, embolism, hemorrhage, or vascular insufficiency. The concept of cerebral vascular insufficiency which explains many of the transient neurological disorders is caused by disturbances of the systemic circulation in the presence of cerebral artery narrowing.
Rothenberg SF, Corday E. ETIOLOGY OF THE TRANSIENT CEREBRAL STROKE. JAMA. 1957;164(18):2005-2008. doi:10.1001/jama.1957.02980180007002