Neurocognitive sequelae of a giant arachnoid cyst: case study.

We conducted a comprehensive neuropsychological evaluation of a normally functioning man with a giant arachnoid cyst encompassing much of the space normally occupied by the left hemisphere. Although of solidly average intellectual ability, the patient demonstrated neurocognitive deficits only revealed upon neuropsychological assessment. Despite the remarkable left hemisphere lesion, the pattern of cognitive dysfunction suggested right hemisphere pathology. We review the arachnoid cyst literature and discuss the possibility of a crowding phenomenon by which language function relocates to the more viable hemisphere. This case illustrates striking preservation of higher cognition in the presence of substantial structural abnormality.