gms | German Medical Science

Objective: Transcranial magnetic stimulation (TMS) is the only non-invasive neurophysiological method for presurgical stimulation mapping of cortical function. Recent technical advances have significantly increased the focal usefulness of this technique. This study aims to compare the accuracy of preoperative nTMS motor mapping and functional magnetic resonance imaging (fMRI) in patients with lesions of the motor cortex.

Method: Between 2010 and 2012 41 patients were successfully mapped preoperatively with nTMS at 110% of the individual motor threshold and underwent fMRI at the same time. The evaluated muscles were identical (APB, ADM, FCR) for the upper limb and for the lower limb (TA, TS). Borders between the outlined motor eloquent regions were compared between the two methods. All results are presented as mean ± standard deviation.

Results: The mean distance between the nTMS and fMRI borders for the upper limb were 8.1±7.8 mm and for the lower limb 14.6±11.9 mm. 17 of the 41 patients showed a preoperative motor deficit. In addition to the 41 patients, fMRI was intended in further 13 patients but failed without an evaluable outcome due to the general condition of the patients or because of hemiplegia or poor co-orporation of the patient. However, nTMS was possible in all of these 13 cases. Of these 41 remaining cases, 2 were arteriovenous malformations (AVM), 7 astrocytomas WHO°II, 7 astrocytomas WHO°III, 27 glioblastomas and 8 had other lesions (metastases, cavernomas).

Conclusions: The accuracy of preoperative nTMS agreed well with the fMRI and was possible for a larger number of patients with tumours in eloquent motor areas than fMRI. Hence this study shows that nTMS is at least as accurate as fMRI but allows the evaluation of all patients independent of the patients' condition.