Validation of the Wechsler Memory Scale-III in a population of people with intractable temporal lobe epilepsy

Abstract

The Wechsler Memory Scale-Third Edition (WMS-III) was developed to overcome the limitations of the Wechsler Memory Scale-Revised and is now routinely used for pre-surgical assessment of memory for patients considering elective surgery for the relief of temporal lobe epilepsy (TLE). We investigated the validity of this relatively new measure in a population of people with resistant TLE. The sample consisted of 99 patients with a diagnosis if TLE in which the epileptogenic focus was clearly identified and localised to either the right or left hemisphere. Patients underwent a full neuropsychological assessment as part of their pre-surgical investigation, including the WMS-III. Patients with right temporal focus had significantly lower scores on the visual immediate and delayed indices of the WMS-III than they did on the corresponding auditory indices. The left temporal focal epilepsy group, however, showed no significant disparity between auditory and visual scores. The overall scores of the WMS-III were significantly lower than the normative data from the WMS-III standardisation samples. Like its predecessor the Wechsler Memory Scale-Revised, the WMS-III has limited value in identifying particular memory deficits associated with either left and right temporal lobe focus. The results of the WMS-III show that it is capable of lateralising to right hemispheric impairment but is more problematic in the assessment of left hemispheric impairment. The visual verbal discrepancy has questionable validity. The search for reliable and valid measures to distinguish between left and right temporal epileptic focus continues.