MAGNETIC SOURCE IMAGING COMBINED WITH IMAGE-GUIDED FRAMELESS STEREOTAXY - A NEW METHOD IN SURGERY AROUND THE MOTOR STRIP

OBJECTIVE: In this study, information about the localization of the ce ntral sulcus obtained by magnetic source imaging (MSI) was intraoperat ively translated to the brain, using frameless image-guided stereotaxy . In the past, the MSI results could be translated to the surgical spa ce only by indirect methods (e.g., the comparison of the MSI results, displayed in surface renderings, with bony landmarks or blood vessels on the exposed brain surface). METHODS: Somatosensory evoked fields we re recorded with a MAGNES II biomagnetometer (Biomagnetic Technologies Inc., San Diego, CA). Using the single equivalent current dipole mode l, the localization of the somatosensory cortex was superimposed on ma gnetic resonance imaging with a self-developed contour fit program. Th e magnetic resonance image set containing the magnetoencephalographic dipole was then transferred to a frameless image-guided stereotactic s ystem. Intraoperatively, the gyrus containing the dipole was identifie d as the postcentral gyrus, using neuronavigation, and the next anteri or sulcus was regarded as the central sulcus. With intraoperative cort ical recording of somatosensory evoked potentials, this assumption was verified in each case. RESULTS: In all cases, the preoperatively assu med localization of the central sulcus and motor cortex with MSI agree d with the intraoperative identification of the central sulcus using t he phase reversal technique. CONCLUSION: The combined use of MSI and a frameless stereotactic system allows a fast orientation of eloquent b rain areas during surgery. This may contribute to a safer and more rad ical surgery in lesions adjacent to the motor cortex.