Pathogenesis and Natural History of Transient Global Amnesia

Abstract

Fourteen patients aged between 49 and 92 years who had suffered from one or more attacks of transient global amnesia (TGA) have been followed for a mean interval of 30 months. Thirteen patients had one or more risk factors for cerebrovascular disease, such as hypertension, cardiac abnormalities, diabetes and hyperlipidemia. Clinical evidence for vertebrobasilar arterial insufficiency was demonstrated in 11 cases. EEG examination revealed bitemporal or bioccipital slow wave activity. Four-vessel arteriography showed atherosclerotic, stenotic, or occlusive lesions predominantly in the vertebrobasilar and posterior cerebral arterial systems. Five patients without recurrence of TGA showed no permanent impairment of memory, whereas eight who had recurrent attacks of TGA showed permanent memory impairment as well as mild visual-spatial or visual-motor dyspraxia as judged by neuropsychological tests on follow-up visits. "Amnesic stroke" with permanent and gross memory defect and dyspraxia occurred in two patients. It is concluded that the majority of transient global amnesic episodes in the elderly or in those with the risk factors listed above result from cerebrovascular insufficiency particularly in the territory of vertebrobasilar and posterior cerebral arterial systems (which supply major portions of the ascending reticular activating system, parahippocampal-fornical-mamillary system, inferomedial aspects of the temporal lobe and occipital lobe). Repeated attacks of TGA are not rare and with each attack the likelihood increases of permanent memory deficits and progressive dementia. A rarer outcome is cerebral infarction in the territory of posterior cerebral arteries commonly referred to as "amnesic stroke."