gms | German Medical Science

Objective: Navigated brain stimulation (NBS) is a newly evolving technique. Except for its supposed purpose, e.g. for preoperative mapping of the central region, little is known about its accuracy compared to more commonly used modalities like direct cortical stimulation (DCS) and functional MRI (fMRI).

Methods: We examined 14 patients with tumors in or close to the precentral gyrus as well as 12 cases of lesions in the subcortical white matter motor tract using NBS for motor cortex characterization.

Results: In the 14 cases of lesions within the precentral gyrus, preoperative motor cortex characterization correlated well with intraoperative DCS with a deviation of 4.4 ± 3.4 mm. Comparing NBS with fMRI, however, deviation was quite larger with 9.8 ± 8.5 mm for upper and 14.7 ± 12.4 mm for lower extremity. In 13 out of 14 cases the surgeon admitted easier identification of the central region whereas it increased confidence in 7 cases. In 5 out of 14 cases, the surgeon recognized a positive influence from the NBS data on the operative result, while it even changed the resection strategy in 2 cases. In 12 patients with subcortical lesions, DTI fiber tracking was performed using NBS mapping as seed region, which resulted in a subjectively more specific presentation of the corticospinal tract compared to conventional fiber tracking. In combination with navigated subcortical mapping, these data are quite useful to confirm each other during resection. One out of 26 patients experienced NBS to be "unpleasant", no one as "painful".

Conclusions: NBS correlates well with DCS as gold standard despite factors, which are supposed to contribute to inaccuracy of the method. Moreover, NBS is shown to be accepted by the surgeon as an additional and helpful modality during resection of tumors within motor eloquent areas but also during preoperative planning.