A 54-year-old woman without significant past medical history presented to the emergency department accompanied by her friend, who had become concerned when the patient repeatedly asked questions that had already been answered. The patient complained of a mild headache and difficulty remembering events of the previous 5 to 6 hours. There were no focal deficits on neurological examination. The patient’s symptoms resolved 10 hours after onset. MRI was performed the following day, which revealed a punctate focus of restricted diffusion in the left hippocampus (arrows, A [diffusion-weighted imaging (DWI)] and B [apparent diffusion coefficient (ADC)]) without corresponding fluid-attenuated inversion recovery (FLAIR) abnormality (C). Given the clinical presentation and imaging findings, the patient was diagnosed with transient global amnesia (TGA).
Transient global amnesia is a self-limiting process that typically lasts a few hours. Clinically, patients present with sudden onset of amnesia, which is predominantly antegrade with a lesser degree of retrograde amnesia. This may be accompanied by more generalized symptoms, such as headache or nausea, but not focal neurological deficits. Symptoms resolve within 24 hours and occur in the absence of seizure activity or head trauma.1 Some have proposed a vascular mechanism, but the etiology of TGA remains unclear.2
The imaging findings associated with TGA consist of solitary or multiple punctate foci of restricted diffusion within the hippocampus, unilateral or bilateral. These findings are transient and may be seen after the patient’s symptoms have resolved, depending on the timing of imaging.3 Although TGA is a clinical diagnosis, imaging may help in its confirmation.
Bailey M, Vartevan A. JAOCR at the Viewbox: Transient Global Amnesia. J Am Osteopath Coll Radiol. 2018;7(4):27.