Lesion topography of posterior cerebral artery infarcts

The Amnestic Syndrome of Posterior Cerebral Artery Infarction

OBJECTIVE

Little is known about the character and underlying lesions of ischemic amnesia. We therefore studied episodic memory functions and brain lesions in 84 patients with acute ischemic infarcts in the supply territory of the posterior cerebral artery (PCA). We also aimed to learn how the neural memory systems are organized.

METHODS

Standard neuropsychological tests were used to assess verbal and figural memory. Patients were split in memory-impaired and memory-intact. Lesions were demarcated, normalized and anatomically labeled, using standard mapping procedures.

RESULTS

Of the 84 patients more than 80% had an amnestic syndrome, mostly with combined, less often with figural or verbal memory impairment. Amnesia in subjects with left hemispheric lesions was more frequent and more severe, with significantly lower scores on the verbal memory test. Normal performance or figural amnesia were prevalent after right hemispheric lesions. However, no amnesia subtype was strictly tied to left- or right-sided brain damage. Hippocampal and thalamic lesions were common, but 30% of lesions were extrahippocampal located in the ventral occipito-temporal cortex and long occipital white matter tracts. Most amnestic-patients lacked awareness for their memory impairment.

CONCLUSIONS

Memory impairment is a key clinical manifestation of acute PCA stroke. Amnesia is more frequent and more severe after left stroke, suggesting a left hemisphere dominance of the two memory systems. Domain specific memory appears not strictly lateralized, since deficits in verbal and figural memory were found after lesions of both sides. Extrahippocampal lesions may also cause memory impairment.