Visuo-spatial memory tests in right temporal lobe epilepsy foci: Clinical validity

ObjectiveTo examine the appropriateness of visual memory tests as an identification method for right mesial temporal lobe dysfunctions in an epilepsy patient group and to study the relationship and possible overlap with non-memory cognitive domains and demographic variables.MethodsEighty preoperative candidates with mesial temporal lobe epilepsy (TLE) were examined using the “Corsi Block-Tapping Test”, “Diagnosticum für Cerebralschädigung” (DCS), the path subtest of the “Verbaler und Visueller Merkfähigkeitstest” (VVM), and the Rey-Osterrieth Complex Figure Test (ROCF). Factorial analyses were performed on raw scores to determine the effect of epilepsy-related variables, interictal epileptiform discharges (IEDs) and presence of cortical dysgenesis, on visual and verbal memory parameters. Sensitivity, specificity and Receiver Operating Characteristic (ROC) curves were calculated based on normative data. Furthermore, Spearman correlations between memory and non-memory cognitive tasks were performed.ResultsThe scores for test sensitivity and specificity and the ROC curves illustrate the tests' poor capacity to lateralize the functional deficit zone even when epilepsy-related factors, such as cortical dysgenesis or presence of contralateral IEDs were controlled. Significant correlations were found between the visual memory measures and nonverbal reasoning, processing speed, attentional flexibility, and visual planning.ConclusionThese neuropsychological tests are not sensitive enough to lateralize the epileptogenic focus in temporal lobe epilepsy patients since in addition to learning and consolidation processes, they measure additional cognitive domains. These results have implications for clinical neuropsychologists, in terms of test choice and the interpretation in the context of presurgical diagnostics.

► The validity of visuo-spatial memory tests in temporal lobe epilepsy was examined. ► Four tests were not sensitive enough to lateralize visuo-spatial memory. ► Presence of epilepsy-related factors did not influence the diagnostic utility. ► We assume that these instruments are influenced by cognitive domains beyond memory.