Surgical treatment of adult patients with thalamic tumors with the aid of tractography, fMRI, transcranial electrical stimulation and direct electrical stimulation of the subcortical white matter

Abstract

The aim of investigation was to assess treatment outcomes in adult patients with thalamic tumors, operated on with the aid of tractography (DTI) and monitoring of motor evoked potentials (MEPs) generated due to transcranial electrical stimulation (TES) and direct electrical stimulation (DES) of the subcortical white matter.
38 subsequent patients with thalamic tumors were operated on using tractography (DTI)- integrated neuronavigation, transcranial electrical stimulation (TES) and direct electrical stimulation (DES). The volumetric method was used to calculate pre- and postoperative tumor volume.
Total tumor resection (100%) was performed in 18 (47%) patients, subtotal in 9 (24%)
(mean extent of resection 89.4%) and partial in 11 (29%) patients (mean extent of resection 77.18%). The mean extent of resection for all surgical patients was 86.5%.
Two (5.2%) patients died postoperatively. Preoperative hemiparesis was present in 18
(47%) patients. Postoperative hemiparesis was observed in 11 (29%) patients of whom only in 5 (13%) new paresis was noted due to surgical intervention. In patients with hemiparesis significantly more frequently larger tumor volume was detected preoperatively. Low mean normal fractional anisotropy (nFA) values in the internal capsule were observed statistically significantly more frequently in patients with preoperative hemiparesis as compared to the internal capsule of the unaffected hemisphere. Transcranial electrical stimulation helps to predict postoperative paresis of extremities. Direct electrical stimulation is an effective tool for intraoperative localization of the internal capsule thus helping to avoid postoperative deficit.
In patients with tumor grade I and II the median time to tumor progression was 36
months. In the case of patients with grades III and IV it was 14 months. The median survival time in patients with grades I and II it was 60 months. In patients with grades III and IV it was 18 months. Basing on our results, patients with glioma grade I/II according to WHO classification are the best candidates for surgical treatment of thalamic tumors. In this group of the patients more often resection is radical, median time to progression and survival time are longer than in patients with gliomas grade III and IV. Within a 7-year follow-up none of the patients with GI/GII grade glioma died.