Abstracts

Rationale: Neuropsychological testing of memory function is often used to lateralize lesion side in patients with medically refractory epilepsy. We analyzed the role of four combined verbal and nonverbal memory tests in lateralizing lesion side in patients with medically refractory epilepsy associated with unilateral mesial temporal sclerosis (uMTS). Methods: We included all cases of unilateral MTS that underwent video-EEG monitoring in our service between Jan1999 and Mar2008. Exclusion criteria were <6 years of education, IQ <70, ages <16 or >55, uncompensated psychiatric disease, additional MRI lesions and extratemporal ictal or interictal epileptiform activity. A group of normal individuals matched for age, gender and education served as a control group. Patients and controls underwent a comprehensive neuropsychological battery that included verbal (RAVLT and logical memory subtests) and nonverbal memory (RDVLT and Complex Rey Figure) tests. For each patient, performance in each test was scored as 0, 1 or 2, according to the number of standard deviations below controls’ performance. A verbal memory score, ranging from 0-8, was defined by the summated scores of RAVLT6, RAVLT7, immediate and delayed recall in the logical memory test. A nonverbal score, also ranging 0-8, was defined as the sum of RDVLT6, RDVLT7, immediate and delayed recall of the Rey Complex Figure scores. Scores above 3 were considered as indicative of function impairement. We calculated sensitivity, specificity, positive and negative predictive powers for a left sided lesion and impaired verbal memory performance, as well as for a right sided lesion and nonverbal memory impairment. Results: We studied 110 patients with uMTS (56 or 49% right MTS) and 26 controls. Groups did not differ in relation to gender (R=50%; L=54%; C=50% women), age (R=37.2; L=37.7; C=40.1 yrs) and education (R=11.6; L=11.3; C=11.2 yrs). Verbal memory impairment was seen in C=2/26, 7.7%; R=14/56, 23.2% and L=25/54, 46.3% (p=0.02 Lvs.C). Nonverbal memory impairment was seen in C=4/26, 15.4%; R=14/56, 25% and L=4/54 7.4% p=0.10). Se=46%, Sp=75%, PPV=64% and NPV=59% were low for verbal memory impairment. For nonverbal memory, although Sp was good at 93%, Se=25%, PPV=54% and NPV=78% were also low. Conclusions: In this large sample of uMTS patients, performance in traditional neuropsychological tests of verbal and nonverbal memory was not a good lateralizing tool. Caution should be exercised when using these neuropsychological tests of verbal and nonverbal memory as a lateralizing tool in uMTS patients.