Cortical mapping with navigated transcranial magnetic stimulation in low-grade glioma surgery.
Transcranial magnetic stimulation (TMS) is a promising method for both investigation and therapeutic treatment of psychiatric and neurologic disorders and, more recently, for brain mapping. This study describes the application of navigated TMS for motor cortex mapping in patients with a brain tumor located close to the precentral gyrus.


METHODS
In this prospective study, six patients with low-grade gliomas in or near the precentral gyrus underwent TMS, and their motor responses were correlated to locations in the cortex around the lesion, generating a functional map overlaid on three-dimensional magnetic resonance imaging (MRI) scans of the brain. To determine the accuracy of this new method, we compared TMS mapping with the gold standard mapping with direct cortical electrical stimulation in surgery. The same navigation system and TMS-generated map were used during the surgical resection procedure.


RESULTS
The motor cortex could be clearly mapped using both methods. The locations corresponding to the hand and forearm, found during intraoperative mapping, showed a close spatial relationship to the homotopic areas identified by TMS mapping. The mean distance between TMS and direct cortical electrical stimulation (DES) was 4.16 ± 1.02 mm (range: 2.56-5.27 mm).


CONCLUSIONS
Preoperative mapping of the motor cortex with navigated TMS prior to brain tumor resection is a useful presurgical planning tool with good accuracy.
Division of Functional Neurosurgery, Hospital das Clinicas, University of São Paulo School of Medicine, São Paulo, Brazil.
Wellingson S
WS
Paiva
Erich T
ET
Fonoff
Marco A
MA
Marcolin
Hector N
HN
Cabrera
Manoel J
MJ
Teixeira