Navigate Transcranial Magnetic Stimulation Is More Reliable Than Tractography for Placing Subdural Electrodes Used for Cortico-Cortical-Evoked-Potentials Recording.

OBJECTIVE

The aim of the study is to verify whether preoperative navigated transcranial magnetic stimulation (nTMS) is a reliable tool for the positioning of subdural electrodes for cortico-cortical evoked potentials (CCEPs) recording in the presence of minicraniotomy.

METHODS

This is a monocentric, prospective, observational cohort study in which we included adults with lesions that were compressing or infiltrating the perisylvian area. In the preoperative phase, we performed nTMS to identify language areas. During the intervention, we performed CCEP recordings using subdural strip electrodes positioned according to the surgical conditions or according to nTMS indications or in accordance with tractography. CCEPs were recorded continuously throughout the intervention with the exception of the phases in which it was necessary to monitor a different type of evoked potential. To evaluate the association between the possibility of registering CCEPs and the method used for the positioning of the subdural electrodes, the patients were dichotomized as CCEP present and CCEP not identifiable.

RESULTS

We evaluated 33 subjects, but only 28 were included in the analysis. No statistically significant differences were present between these two patient groups. The CCEPs were substantially stable during the surgical procedure in 25 patients (89.3%). When the strip was positioned according to nTMS (n°:24/28; 85.7%), CCEPs were always identiable. However, when the strip was positioned according to tractography, CCEPs were not identifiable in 4 subjects (14.4%).

CONCLUSIONS

Compared to tractography, nTMS shows a higher reliability in the placement of subdural electrodes used for CCEP recordings.