Differential effects of temporal pole resection with amygdalohippocampectomy versus selective amygdalohippocampectomy on material-specific memory in patients with mesial temporal lobe epilepsy

Purpose: In the surgical treatment of mesial temporal lobe epilepsy, there is converging evidence that individually tailored or selective approaches have a favorable cognitive outcome compared to standard resections. There is, however, also evidence that due to collateral damage, selective surgery can be less selective than suggested. As part of a prospective transregional research project the present study evaluated the outcome in memory and nonmemory functions, following two selective approaches: a combined temporal pole resection with amygdalohippocampectomy (TPR+) and transsylvian selective amygdalohippocampectomy (SAH). Methods: One year after surgery, cognitive outcomes of postoperatively seizure-free patients with mesial TLE and hippocampal sclerosis, who underwent either TPR+ (N = 35) or SAH (N = 62) in two German epilepsy centers (Bonn/Berlin), were compared. Results: Repeated measurement MANOVA and separate post hoc testing indicated a double dissociation of verbal/figural memory outcome as dependent on side and type of surgery. Verbal memory outcome was worse after left-sided operation, but especially for SAH, whereas figural memory outcome was worse after right-sided operation, preferentially for TPR+. Attention improved independent of side or type of surgery, and language functions showed some improvement after right-sided surgeries. Discussion: The results indicate a differential effect of left/right SAH versus TPR+ on material-specific memory insofar as transsylvian SAH appears to be favorable in right and TPR+ in left MTLE. The different outcomes are discussed in terms of a different surgical affection of the temporal pole and stem, and different roles of these structures for verbal and figural memory.