Low prevalence but high specificity of material-specific memory impairment in epilepsy associated with hippocampal sclerosis.

PURPOSE: Material-specific memory impairment is used as a lateralizing tool in the evaluation of temporal lobe epilepsy. Lateralizing ability of material-specific memory deficits in temporal lobe epilepsy remains controversial. METHODS: We studied memory impairment profiles of verbal and nonverbal memory deficits with eight memory subtests of four neuropsychological instruments (two verbal and two nonverbal) in 87 right-handed patients with epilepsy associated with unilateral mesial temporal sclerosis (MTS; 44 right - R, 43 left - L) and 42 controls, with an IQ >70, at least 8 years of education, and without comorbidities. KEY FINDINGS: Selective verbal memory impairment was noted in 11 of 43 or 25.6% of left MTS cases, with 82.2% specificity, whereas selective nonverbal memory impairment was noted in 11 of 42 or 26.2% of right MTS cases, with 92% specificity. Nonlateralizing profiles of memory performance were seen in the remaining 65 of 87 patients. Approximately half (46/87 or 52.9%) of the patients had intact memory function in both modalities, equally distributed between patients with right MTS (23/44) and left MTS (23/43). Global impairment of both memory types was seen in 12 of 87 or 13.8% of patients, equally distributed between the two groups (7/43 left and 5/44 right). SIGNIFICANCE: Lateralizing profiles of selective verbal and nonverbal memory deficits are highly specific for left and right MTS, although infrequently encountered in our patients. Nonlateralizing profiles predominated in this population. These findings suggest hemispheric asymmetry memory function, with complex functional interaction of the hippocampi, and possible compensatory mechanisms in the setting of a unilateral lesion.

Contralateral interictal and ictal EEG epileptiform activity accentuate memory impairment in unilateral mesial temporal sclerosis patients.

OBJECTIVE: 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 memory in unilateral MTS (uMTS) patients. METHOD: Retrospective review of 121 right-handed uMTS patients (69 left) evaluated with prolonged video-EEG and verbal and nonverbal memory tests (Rey Auditory Verbal Learning Test and Rey-Osterrieth Complex figure), with additional very delayed trials. Patients were classified according to ictal/interictal EEG findings and MTS side as left or right concordant or discordant. Thirty-nine normal individuals who underwent the same neuropsychological battery served as controls. RESULTS: Demographic, disease, and treatment features did not differ among groups. On the 7-day verbal memory free recall, left discordant performed significantly worse than controls and right concordant, recognized fewer words, and had more recognition errors than all other groups, including left concordant. For nonverbal memory, right discordant performed significantly worse than controls on delayed recall, and attained lower scores than other groups on immediate and 7-day recall, but this difference did not reach statistical significance. Left discordant had higher scores of memory complaints than controls and disclosed a trend toward accentuated memory impairment compared with the other groups over time. CONCLUSIONS: Our results suggest that contralateral electrographic involvement in uMTS was associated with more pronounced memory impairment for verbal material in left discordant patients, and to a lesser extent, for nonverbal material in right discordant patients. Left discordant group also had increased memory complaints. (PsycINFO Database Record