Cerebral blood flow changes in orthostatic dysregulation fainters.

The changes in blood flow of both the internal carotid and the vertebral artery during orthostatic test with or without fainting attack were studied in 25 healthy children and 30 patients with orthostatic dysregulation (OD). In healthy children and non-fainted OD patients, no change in blood flow occurred in either the internal carotid artery or the vertebral artery during orthostatic test. On the other hand, a significant decrease in blood flow of the internal carotid artery and/or the vertebral artery occurred during fainting of OD patients. These data suggest that three mechanisms might be involved in fainting of OD patients; a decrease in blood flow of the internal carotid artery, the vertebral artery and a decrease in blood flow of both these arteries.