Transient aphasia and persistent amnesia after surgery for internal carotid artery--posterior communicating artery aneurysm.

We report a case of transient aphasia and persistent amnesia after clipping of a ruptured cerebral aneurysm to treat a subarachnoid hemorrhage. Postoperatively, aphasia was identified and magnetic resonance imaging (MRI) showed an abnormal intensity area in the left anterior thalamus. Single photon emission computed tomography (SPECT) revealed a wider area of low perfusion surrounding the left thalamus and left frontotemporal lobe than that shown by the MRI. His aphasia resolved over the subsequent 12-week period. He was left with an isolated disturbance of memory; in the absence of any dementia, aphasia or disturbance of consciousness, his condition was classified as one of amnesia. SPECT 14 weeks after admission revealed an area of low perfusion limited to the left thalamus. These findings suggest that the persistence of amnesia in this case was caused by the infarction of the mammillothalamic tract, and the recovery from aphasia may have resulted from the disappearance of surrounding edema.