gms | German Medical Science

Objective: Since the functional outcome after brain tumour resection is of crucial importance for the patients' adjuvant treatment and quality of life, the indication for the resection of tumours, involving motor-eloquent brain areas, should be made with extreme care. Precise preoperative delineation of (i) the primary motor representation and (ii) the margins of the metabolically highly-active tumour parts can facilitate risk-evaluation and may encourage the surgeon to push the resection towards the margins of motor-eloquent regions.

Method: 27 patients (age: 55 ± 13 years) with malignant gliomas (grade IV: N=21; grade III: N=6) were consecutively allocated to a prospective trial and were investigated by navigated transcranial magnetic stimulation (nTMS; Nexstim 4.2), functional MRI (Siemens Trio), nTMS-based DTI tractography (iPlan Net) and O-(2-[¹⁸F]Fluoroethyl)-L-tyrosine positron emission tomography (FET-PET) prior to surgery. Intraoperatively, fluorescence-guidence (5-aminolevolinic acid), neuronavigation including functional and metabolic data and direct (sub-)cortical stimulation using a monopolar electrode were applied. Motor functioning was assessed before surgery and at discharge. Any residual contrast enhancement in the postoperative MRI scan (0-48 hrs after surgery) was regarded as tumour remnant.

Results: 52% of the patients had preoperative motor deficits. At discharge, the paresis had improved in 26% and worsened in 11% of the cases (N=3), 63% remained unchanged. Of the three cases with postoperative deterioration of motor functions, two had postcentrally located tumours and in two of the three cases a residual contrast enhancement was observed in the postoperative MRI scan. In general, total resection was planned in 21 cases (78%). This was achieved in N=14/21, in 7 patients parts of the tumour were not resected, partly according to the intraoperative stimulation results.

Conclusions: In this study, the rate of newly occuring postoperative motor deficits is within the lower range compared with previous publications dealing with rolandic tumour surgery (6 - 34 %; Frey et al., 2014; Krieg et al., 2014). Despite the highly critical tumour location, the rate of total resection was within the usual range published for fluorescence-guided glioma surgery (65 %; Stummer et al., 2006). These results indicate that a multimodal imaging and functional mapping approach is beneficial and well feasible in our experience.