Article
Reliability of functional MRI-integrated neuronavigation
Zuverlässigkeit der Lokalisation der f-MRT Aktivität für die funktionelle Neuronavigation
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Published: | April 23, 2004 |
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Outline
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Objective
A determination of primary motor cortex is required to preserve motor function during surgery in close proximity of the eloquent cortex. Functional MRI utilising the BOLD contrast is a non-invasive tool for this purpose. But the BOLD signal reflects cortical activity only indirectly. In this study we analysed the functional measurements of 30 patients with lesions close to the central sulcus and compared the predicted motor hand area with anatomical and intraoperative electrophysiological findings.
Methods
Preoperative EPI T2* BOLD imaging was performed in a 1,5 T scanner during standardized paradigms for hand, foot and tongue movement (128x128 Matrix, 15 slices, slice thickness 6 mm, gap 0,6 mm, FOV 230 mm, TE 50 ms, TR 5 sec). Data analysis was done with the BrainVoyager software (Brain Innovation, Maastricht, NL). Anatomical scans with gadolinium were acquired for navigation and fused to the functional data sets (BrainLAB, Heimstetten, Germany). Intraoperative cortical stimulation was done with the EWACS IOM System 916, Software Version 2.1 (Inomed, Teningen, Germany) and monopolar current with 50-200 Hz and 5-15 mA.
Results
The functional MRI activity for hand movement was located in the anatomical “hand knob” in all cases. The spatial extent of the fMRI area, depending on the significance level, was spread to the postcentral gyrus in the majority of the cases. Intraoperative cortical stimulation confirmed the predicted location of the central sulcus and localisation of the fMRI hand area in 29 cases. In one case, due to brain shift, no electrocortical correlation was established. In two cases significant motor activation was seen in the postcentral gyrus.
Conclusions
Despite all its methodological limitations, functional MRI has proven to be a reliable mapping tool for non-invasive preoperative localization of motor activity in patients with lesions in close proximity to eloquent motor cortex. Functional localizations may be shifted at the time of tumor resection, therefore electrophysiological methods are still necessary.