Transient global amneisa Diagnostic Imaging

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hasnain Ali Moryani, MBBS.

• Brain imaging is commonly performed to exclude infarction or other structural lesions, especially in the emergency setting.
• Initial imaging studies are usually normal early in the course of the episode.^[1]

Diffusion-Weighted MRI (DWI) – Key Modality

• Most patients have one or more punctate lesions in the hippocampus or adjacent structures on diffusion-weighted MRI^[2].
• In a series of 390 patients, such lesions were seen in about 70% of cases^[2].

Timing of MRI Findings

• Lesions are often not visible immediately after symptom onset^[1][2].

• They are most often detected 12 to 48 hours after the episode^[2].
• The lesions are usually fleeting, but may persist for several days^[2].

Typical Lesion Characteristics

• Lesions are small, punctate areas of restricted diffusion in the hippocampus^[1][2].

• Left-sided lesions have been reported more often than right-sided or bilateral ones^[2].

Atypical / Expanded Patterns

• Unusual anatomical or temporal patterns of diffusion restriction have been described in some patients who did not have the typical clinical syndrome^[3].
• Similar hippocampal lesions may occasionally be found incidentally in patients with cognitive or emotional symptoms without amnesia, leading some authors to broaden the imaging-based definition^[3].

Functional / Perfusion Imaging

• Functional studies have shown bitemporal hypoperfusion during episodes^[4].
• Network analyses demonstrate reduced connectivity of the hippocampi, parahippocampal gyri, amygdala, and parts of the lateral temporal lobe during the attack^[5].