Abstracts

Rationale: 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 - RAVLT and Logical Memory Tests and two nonverbal - RDVLT and Complex Rey Figure) 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 eight years of schooling, without comorbidities. Cut-off levels for performance on each subtests were calculated with ROC analysis, with a cut-off that allowed at least 80% sensibility with the best possible specificity. Selective verbal memory impairment was considered if performance was impaired in two or more subtests of verbal memory and intact performance in at least three nonverbal memory subtests. Selective nonverbal memory impairment was considered if performance was impaired in two or more nonverbal memory subtests, with intact performance in at least three verbal memory subtests. Sensitivity, specificity, positive and negative predicitve values of selective verbal and nonverbal memory impairment were calculated for left and right MTS were calculatedResults: Selective verbal memory impairment was seen in 11/43 or 25.6% of LMTS cases, with a 84.6% specificity, while selective nonverbal memory impairment was seen in 11/42 or 26.2% of RMTS cases, also with a 95.3% specificity. Nonlateralizing profiles of memory performance were seen in 65/87 patients (74.7%). Approximately half (46/87 or 52.9%) of the patients had intact memory function in both modalities, equally distributed between R (23/44) and L (23/43) patients. Global impairment of both memory types was seen in 12/87 or 13.8% of patients, equally distributed between the two groups (7/43 L and 5/44 R). Conclusions: Lateralizing profiles of selective verbal and nonverbal memory deficits are highly specific for L and R MTS, though infrequently encountered in our patients.