gms | German Medical Science

Objective: In dominant temporal lobe epilepsy surgery, language, visual and memory functions are at risk. Patients operated on using preoperative functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) risk maps combined with intraoperative neuronavigation and MR imaging were investigated prospectively in regard to risk reduction for favorable neurological, neuropsychological and seizure outcome.

Method: Thirteen patients had preoperative fMRI for speech- and memory relevant cortical areas and DTI imaging for visual tract localization. Additionally, an intracarotide amobarbital (WADA) test for evaluation of fMRI regarding hemisphere dominance was performed in seven patients. Functional imaging risk maps were preoperatively generated and integrated in a computer based treatment plan and used for neuronavigation guided tailored resection of neocortical and mesial temporal lobe structures. Postoperative neurological, neuropsychological and seizure outcome was measured.

Results: Speech and memory activated cortical areas as well as visual tracts were successfully localized in all patients employing preoperative fMRI and DTI fiber tracking using standard paradigms. The correlation of WADA test and fMRI side dominance was 100%. Integration of functional imaging information into neuronavigation led to gross total resection of the pre-planned target volumes including the lesion as confirmed by intra- and postoperative MR imaging in all patients. None of the patients had postoperative speech disturbances. Although all patients had temporo-mesial resections, memory decline was found in only 2 out of 13 (15.4%) patients, correlating with surgical lesions in fMRI memory activated areas in the posterior para-hippocampal gyrus. Additionally, a postoperative superior visual field defect occurred in one patient (7.7%). An Engel Class 1 seizure outcome was found in 10 patients (77%), nine of them were completely seizure free (FU 9.5 months mean).

Conclusions: The prospective protocol which included functional imaging (speech and memory fMRI, visual tract DTI) in the surgery of the dominant temporal lobe combined with neuronavigation and intraoperative MR imaging led to an excellent neurological, neuropsychological and seizure outcome and a low complication rate.