Teaching NeuroImages: Convexal subarachnoid hemorrhage accompanied by transient global amnesia

A 55-year-old otherwise healthy woman presented with sudden-onset anterograde amnesia, temporal disorientation, and repetitive questioning, which was associated with moderate intensity headache. Consistent with transient global amnesia (TGA), this clinical symptomatology lasted for 8 hours. Brain imaging showed a convexal subarachnoid hemorrhage1 (cSAH) (figure, A) and—characteristic of TGA2—a punctuate diffusion-weighted imaging positive lesion in the right hippocampus on MRI (figure, B and C). Cerebral microbleeds or cortical superficial siderosis were not evident on acute MRI.