Verbal retention lateralizes patients with unilateral temporal lobe epilepsy and bilateral hippocampal atrophy

Purpose: To examine the lateralization utility of preoperative verbal reten tion in patients with and without bilateral hippocampal atrophy. Methods: The sample consisted of 74 patients with EEG- defined unilateral t emporal lobe epilepsy (TLE) who had also undergone volumetric magnetic reso nance imaging (MRI). Verbal retention was operationalized by the Logical Me mory percentage retention subtest (LM%) of the Wechsler Memory Scale. Patie nts were divided into groups with (a) bilaterally normal hippocampal volume s, (b) unilateral atrophy, or re) bilateral atrophy. Two different threshol ds (empirically derived vs. normative) were used to lateralize on the basis of LM%. LM% lateralization was then examined by group using chi (2) sensit ivity, positive predictive values, and odds ratios. Analyses were also cond ucted separately in the subset of patients who were seizure free after surg ery. Results: Mean LM% performance was significantly lower in patients with left versus right TLE in the subset with bilateral hippocampal atrophy (p = 0.0 18), but not in patients with a normal MRI (p = 0.918) or unilateral atroph y (p = 0.087). The odds of a correct lateralization by LM% increased from 1 .67 in patients with normal MRI to 36.11 in patients with bilateral hippoca mpal atrophy. The power of a right and left lateralization prediction by LM % was 100% and 75%, respectively. in patients with bilateral hippocampal at rophy. Similar results were obtained when analysis was restricted to patien ts who were seizure free after surgery. Conclusions: Preoperative: verbal retention as measured by LM% may provide meaningful lateralization information in patients who are difficult to late ralize via MRI.