gms | German Medical Science

Objective: Navigated transcranial magnetic stimulation (nTMS) is used to determine the distribution of eloquent motor areas. As shown in previous studies, there are primary motor areas frontal to the precentral gyrus. However, there is no clear evidence about the importance and eloquence of these areas for surgical considerations. We therefore investigated the correlation between surgically resected nTMS-positive prerolandic motor areas and postsurgical loss of motor function.

Method: 40 patients with gliomas in the precentral or prerolandic cortex where examined with nTMS prior to surgery to determine the localization of the primary motor areas. Based on the fusion of the mapping points with the postsurgical MRI, we identified nTMS-positive points which were resected in the infiltration zone of the tumor. The resected points were then classified into localization and latency of the motor evoked potentials.

Results: The 40 patients with an average age of 57.1 years presented tumor entities consisting of 25 glioblastomas, 8 diffuse and 5 anaplastic astrocytomas, one anaplastic oligodendroglioma and one oligoastrocytoma. Among the 40 patients, 27 showed nTMS-positive motor eloquent points in the prerolandic gyri during nTMS mapping. The resection of nTMS-positive cortical areas led to a considerable number of transient pareses, which we observed in 8 patients with direct postsurgical motor function deficits. In 5 of these patients nTMS points were resected in the prerolandic gyri, in two patients points within the precentral gyrus and one patient was showing a paresis without resection of motor eloquent spots.

Conclusions: Although nTMS identifies a considerably high number of prerolandic motor areas, these should also be considered as highly eloquent and spared during resection.