gms | German Medical Science

Objective: The 3-dimensional magnetic resonance imaging-navigated trancranial magnetic stimulation (nTMS) has been introduced as a novel tool for preoperative functional mapping. First clinical studies in single centers have shown good correlation with intraoperative direct cortical stimulation (DCS), which still represents the gold standard for perioperative functional mapping. With the successful introduction of this system in the clinical trial, more and more hospitals gain access to this method of preoperative planning. We herein present our first experiences and limitations of this novel tool.

Method: All patients with lesions within range of the primary motor area and/or language areas underwent evaluation with nTMS mapping. After nTMS was performed, the navigation exams were used for preoperative planning. Intraoperative DCS was used when the lesion was associated to the primary motor cortex and reconciliation with the navigation exams followed.

Results: Within the first 12 months 51 patients with tumorous lesions within range of motor and/or speech areas underwent nTMS for preoperative motor and/or speech mapping. In 50 cases the surgical resection followed. In 26 cases the tumors were directly associated with the central region. It was able to perform a DCS in 73% of those cases. The intraoperative identification of the gyrus precentralis agreed well (> 90%) when compared to the navigation exams. In two cases the preoperative hemiparesis worsened due to postoperative hemorrhages. Markedly, no postoperative speech disorders occurred. An immediate postoperative improvement of presurgical disorders was seen in over 30% of all patients. An additional beneficial aspect encompasses the patients' experience of an intensive contact with the neurosurgeon and subsequently reduced preoperative anxieties. Nonetheless, the functional mapping has shown some limitations. A valid examination of language associated areas cannot be performed when the patient is incompliant or aphasia is too severe.

Conclusions: The nTMS has proven its benefit for the neurosurgical treatment of intracranial lesions in first clinical studies. In our experience the nTMS improves the preoperative planning, especially when the normal anatomical configurations are altered by the tumor or perifocal edema.