Hippocampal lesion patterns in acute posterior cerebral artery stroke: clinical and MRI findings.

BACKGROUND AND PURPOSE Reports of ischemic stroke affecting the hippocampus are rare. In this study we used diffusion-weighted MRI (DWI) to characterize patients with posterior circulation stroke involving the hippocampus. METHODS Fifty-seven consecutive acute stroke patients with hippocampal infarct (HI) on DWI were analyzed with regard to clinical features and ischemic lesion patterns. The last 20 of these underwent additional neuropsychological testing of short-term, working, and episodic long-term memory. RESULTS We found unilateral HI in 54 and bilateral HI in 3 patients. Visual analysis identified 4 patterns of DWI lesion affecting (1) the complete hippocampus (15/60), (2) the lateral (19/60) or (3) dorsal (22/60) parts of the hippocampal body and tail, and (4) circumscribed lesions in the lateral hippocampus (4/60), corresponding well to hippocampal vascular anatomy. In all cases DWI showed further ischemic lesions in the posterior circulation. Symptoms from lesions outside the hippocampus were the common leading clinical signs. Whereas mnestic deficits were prominent in only 11/57 patients, neuropsychological examination in 20 patients showed deficits of verbal episodic long-term memory in left and of nonverbal episodic long-term memory in right HI. CONCLUSIONS Several phenotypic lesion patterns can be distinguished in HI that usually occur as part of multifocal PCA ischemia. A careful neuropsychological examination is necessary to detect resulting memory deficits.