Acute Amnesic Symptoms Due to Bilateral Fornix Column Infarction: a Case Report

The fornix is a part of the Papez circuit and associated with memory formation. Pure fornix infarction is a very rare type of stroke that causes symptoms such as transient global amnesia (TGA); however, the degree of memory impairment varies. The cause of fornix infarction is often unknown. A right-handed 51-year-old female patient with a current smoking habit and a history of hypertension experienced an acute onset of anterograde amnesia marked by repetitive questions; this episode, which persisted for 24 h, appeared to be TGA. Diffusion-weighted imaging showed acute bilateral fornix column infarction. Fast imaging employing steady-state acquisition (FIESTA) revealed that the subcallosal artery (ScA) was responsible for the fornix column infarction. The etiology of the stroke remained indeterminable despite the comprehensive stroke workup; hence, this case was classified as an embolic stroke of undetermined source. ScA is the perforating branch from the anterior communicating artery. In general, minute perforating branches are not detected by ordinary MRI; however, FIESTA may be useful to detect the ScA. In the present case, FIESTA showed a relatively large ScA, potentially indicating a microembolic etiology. Although we evaluated our patient’s embolic source, it remained indeterminable. Acute amnesic symptoms occasionally occur due to bilateral fornix column infarction, and the resulting memory dysfunction sometimes persists. FIESTA may be useful for imaging the ScA to identify the etiology of stroke.