MRI in the Diagnosis of Transient Global Amnesia: A Case Series and Review of Current Evidence.

Transient global amnesia (TGA) is a common acute amnestic syndrome characterised by sudden-onset predominant anterograde amnesia lasting up to 24 hours. Patients with TGA frequently ask repetitive questions reflecting disorientation and may have some degree of inability to recall general or personal information (retrograde amnesia) while the episode lasts. During the episode of TGA, other cognitive functions are normal. Episodes are self-limited and, by definition, resolve within 24 hours, with recovery of memory function symptoms, except for what happened during the episode. Although diagnosis is primarily clinical, neuroimaging plays a crucial role in excluding alternative causes. Recent evidence suggests that characteristic findings on diffusion-weighted imaging (DWI) may support the diagnosis of TGA. Here, we present three cases of TGA evaluated at Darent Valley Hospital, Kent, UK, with acute onset of confusion and anterograde memory loss. Case 1 was a 53-year-old man who presented to the emergency department with a new onset of confusion, which completely resolved within three hours. Subsequent MRI of the brain showed a punctate area of restricted diffusion involving both hippocampi, which later fully resolved without any residual damage on a follow-up MRI after one week. Case 2 was a 63-year-old woman who became acutely confused while working as a caterer organising a large event. The episode lasted for approximately six to seven hours. MRI of the brain showed a punctate area of restricted diffusion involving the right hippocampus, which fully resolved on an interval MRI scan performed two weeks later. Case 3 was a 59-year-old man who was brought to the hospital due to the sudden onset of confusion noticed by his wife, which lasted for 12 hours. An initial MRI of the brain, conducted four hours after symptom onset, showed no definitive abnormalities. A repeat scan 24 hours after symptom onset revealed an interval appearance of restricted diffusion involving the tail and head of the right and left hippocampi, respectively. All three cases were diagnosed as TGA based on their clinical presentation and MRI findings. The prevalence of typical MRI findings related to TGA varies widely and has been reported to be as high as 85% in some studies. However, these findings may be underdetected without a high index of clinical suspicion from the radiologist. MRI of the brain, in conjunction with clinical history, can improve diagnostic confidence in cases of TGA.