Serial 7 T MRI demonstrates reversible hippocampal T2 abnormalities in transient global amnesia

Area of Science:

• Neurology
• Radiology
• Neuroimaging

Background:

• Transient global amnesia (TGA) is often associated with punctate hippocampal CA1 lesions on diffusion-weighted imaging (DWI).
• The transient nature of these hippocampal lesions in TGA has remained uncertain.
• Ultra-high-field 7-tesla (7T) MRI offers enhanced spatial resolution for detecting and characterizing these lesions.

Purpose of the Study:

• To investigate the temporal evolution of hippocampal T2-weighted imaging (T2WI) abnormalities in TGA using serial 7T MRI.
• To determine if acute TGA lesions are consistently detectable and fully resolve within approximately two weeks.

Main Methods:

• A single-center study included six patients diagnosed with TGA and DWI-confirmed CA1 lesions.
• Serial 7T MRI scans were performed during the acute phase and at 14-18 days follow-up.
• Primary outcome was the complete resolution of hippocampal T2 hyperintensity; secondary outcomes included detection rates and lesion concordance with DWI.

Main Results:

• All six patients exhibited hippocampal CA1 hyperintensity on acute 7T T2WI, correlating with DWI abnormalities.
• Follow-up 7T MRI at 14-18 days showed complete resolution of T2 hyperintensity in all patients.
• No residual signal abnormalities or structural atrophy were observed, and follow-up DWI confirmed the disappearance of diffusion abnormalities.

Conclusions:

• Serial 7T MRI demonstrates that hippocampal T2WI lesions in TGA are acutely visible and uniformly disappear by two weeks.
• These findings provide high-field structural evidence supporting the transient nature of typical TGA.
• The study refines the understanding of hippocampal signal changes in TGA and CA1 vulnerability.