Pre- and Postoperative Verbal Memory and Executive Functioning in Frontal Lobe Epilepsy versus Temporal Lobe Epilepsy

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Neuropsychological assessment has become an important tool in evaluating the preoperative cognitive status and the postoperative cognitive outcome after neurosurgery in patients with focal epilepsy. Even though earlier studies predominantly focused on cognitive functioning in patients with temporal lobe epilepsy (TLE), there is evidence for a great overlap in preoperatively affected cognitive functions between patients with TLE and patients with frontal lobe epilepsy (FLE). The current study aimed to investigate whether it is possible to differentiate between FLE and TLE patients prior to surgery based on different measures that assess verbal memory and executive functioning. Furthermore, since it has been proposed that the two groups develop differently after surgery, the postoperative cognitive development of patients was examined. Pre- and postoperative data of 303 patients with either FLE (n = 109) or TLE (n = 194) was retrospectively analyzed. Preoperative results indicate that the patient groups did not differ on measures of verbal memory functioning. In fact, measures of executive functioning may be more valuable in differentiating FLE from TLE patients. Postoperative findings revealed that there is no distinctive development between patients with FLE and TLE on the assessed cognitive functions. Results rather suggest that the lateralization, not the localization of epileptic activity may be the more important variable in evaluating preoperative presentation and postoperative outcome, at least for measures of verbal memory functioning. Results are discussed in the light of generalization concerns and heterogeneity issues pertaining to the patient groups that were included in this study. In conclusion, the present study adds to the knowledge base on the grounds of which patients may be advised for or against epilepsy surgery.
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