Methodological and technical issues for integrating functional magnetic resonance imaging data in a neuronavigational system

OBJECTIVE: The aim of this article was to analyze the technical and methodo logical issues resulting from the use of functional magnetic resonance imag e (fMRI) data in a frameless stereotactic device for brain tumor or pain su rgery (chronic motor cortex stimulation). METHODS: A total of 32 candidates, 26 for brain tumor surgery and six chron ic motor cortex stimulation, were studied by fMRI scanning (61 procedures) and intraoperative cortical brain mapping under general anesthesia. The fMR I data obtained were analyzed with the Statistical Parametric Mapping 99 so ftware, with an initial analysis threshold corresponding to P < 0.001. Subs equently, the fMRI data were registered in a frameless stereotactic neurona vigational device and correlated to brain mapping. RESULTS: Correspondence between fMRI-activated areas and cortical mapping i n primary motor areas was good in 28 patients (87%), although fMRI-activate d areas were highly dependent on the choice of paradigms and analysis thres holds. Primary sensory- and secondary motor-activated areas were not correl ated to cortical brain mapping. Functional mislocalization as a result of i nsufficient correction of the echo-planar distortion was identified in four patients (13 %). Analysis thresholds (from P < 0.0001 to P < 10(-12)) more restrictive than the initial threshold (P < 0.001) had to be used in 25 of the 28 patients studied, so that fMRI motor data could be matched to corti cal mapping spatial data. These analysis thresholds were not predictable pr eoperatively. Maximal tumor resection was accomplished in all patients with brain tumors. Chronic motor cortex electrode placement was successful in e ach patient (significant pain relief > 50% on the visual analog pain scale) . CONCLUSION: In brain tumor surgery, fMRI data are helpful in surgical plann ing and guiding intraoperative brain mapping. The registration of fMRI data in anatomic slices or in the frameless stereotactic neu ro navigational de vice, however, remained a potential source of functional mislocalization. E lectrode placement for chronic motor cortex stimulation is a good indicatio n to use fMRI data registered in a neuronavigational system and could repla ce somatosensory evoked potentials in detection of the central sulcus.