To describe a case of recurrent transient global amnesia (TGA) with temporally spaced bilateral hippocampal restricted diffusion on MRI.

TGA is defined as a sudden onset of anterograde and retrograde amnesia that lasts 24 hours, and can recur over time. Multiple mechanisms have been proposed to explain this condition, including cortical spreading depression, venous congestion, hypoxic-ischemic events, epileptic phenomena, and ineffective connectivity in bilateral hippocampal structures (subiculum-fimbria, entorhinal cortex-CA4) due to vascular impairment.

Bilateral hippocampal involvement has been described in the setting of TGA with focal mesial hippocampal diffusion restriction in diffusion-weighted imaging (DWI). Herein we postulate that recurrent TGA results from neuroanatomical network and vascular supply impairment.

A 59-year woman with history of head injury in her 30s, migraine, B12 deficiency, benign paroxysmal positional vertigo, degenerative spine disease, post-traumatic stress disorder, and tobacco use, presented with typical symptoms of TGA. Brain MRI demonstrated punctate restricted diffusion in the right hippocampus. A repeat MRI sixteen months after showed complete resolution in DWI. The patient presented with a second similar episode twelve months later; MRI demonstrated punctate lesions in DWI in the left hippocampus. The patient had a negative evaluation for stroke and epilepsy. Of note the patient did report a migraine during each episode.