Chronic hippocampal subfield damage in transient global amnesia revealed by 7T MRI: All is not reversible?

Abstract

Transient global amnesia (TGA) is a neurological condition characterized by temporary memory loss and classically associated with a reversible unilateral punctate focus of restricted diffusion in the cornu ammonis 1 (CA1) region of the hippocampus. Historically, the lesions were considered to be transient in nature with no long-term imaging abnormality. However, more recent studies have challenged the concept that there are no long-term neurological sequelae. In line with this evidence, we explore the role of ultra-high-resolution imaging using 7 Tesla MRI to evaluate for long-term imaging abnormalities in a 63-year-old woman with a typical clinical course and acute TGA imaging findings. The 7 Tesla MRI revealed a residual lesion on susceptibility-weighted imaging (SWI) with evidence of gliosis and volume loss at the site of the acute lesion in CA1 eight months after the acute episode. This case challenges the traditional mantra of TGA as a fully reversible condition with no long-term imaging findings, suggesting the need for further research using ultra-high-field MRI to determine TGA's potential long-term imaging sequelae and any association with neurocognitive sequelae.