Abstracts

Rationale: Memory impairment is a recognized complication of mesial temporal sclerosis (MTS). Epileptiform activity may negatively impact on cognition. We evaluated the impact of contralateral EEG involvement on cognition in unilateral MTS (uMTS) patients. Methods: We retrospectively studied 121 right-handed patients with uMTS (69 left) and 39 controls. Patients underwent video-EEG monitoring and memory testing with verbal (Rey Auditory Verbal Learning Test), nonverbal memory (Rey-Osterrieth Complex figure), with additional very delayed trials for both tests, and memory complaint questionnaire. Patients were classified according to ictal/interictal EEG as left or right concordant (LC, RC) or discordant (LD, RC). Results: Demographic, disease and treatment features did not differ among groups. On 7-day free-recall, LD performed significantly worse than controls and RC, recognized fewer words and had more recognition errors than all other groups, including LC. For nonverbal memory, RD performed significantly worse than C on delayed recall, and attained lower scores than other groups on immediate and 7-day recall, but this difference did not reach statistical significance. LD had higher score of memory complaints than controls. Conclusions: Contralateral EEG involvement in uMTS was associated with accelerated forgetting of verbal material in LD patients, to a lesser extent, of nonverbal material in RD patients, and increased memory complaints for LD group. These findings indicate bilateral representation of verbal and nonverbal memory, with language dominant hemisphere predominance for verbal memory and, less pronouncedly, non-language dominant hemisphere predominance for nonverbal memory. Contralateral electrographic involvement accentuates memory impairment, in a material-specific manner, resulting in accelerated forgetting.