Localization of somatosensory function by using positron emission tomography scanning: a comparison with intraoperative cortical stimulation

Object. To investigate the utility of [O-15]H2O positron emission tomograph y (PET) activation studies in the presurgical mapping of primary somatosens ory cortex, the authors compared the magnitude and location of activation f oci obtained using PET scanning with the results of intraoperative cortical stimulation (ICS). Methods. The authors used PET scanning and vibrotactile stimulation (of the face, hand, or foot) to localize the primary somatosensory cortex before s urgical resection of mass lesions or epileptogenic foci affecting the centr al area in 20 patients. With the aid of image-guided surgical systems, the locations of significant activation foci on PET scanning were compared with those of positive ICS performed at craniotomy after the patient had receiv ed a local anesthetic agent. In addition, the relationship between the magn itude and statistical significance of blood flow changes and the presence o f positive ICS was examined. In 22 (95.6%) of 23 statistically significant (p < 0.05) PET activation foc i, spatially concordant sites on ICS were also observed. Intraoperative cor tical stimulation was positive in 40% of the PET activation studies that di d not result in statistically significant activation. In the patients showi ng these results, there was a clearly identifiable t-statistic peak that wa s spatially concordant with the site of positive ICS in the sensorimotor ar ea. All PET activation foci with a t statistic greater than 4.75 were assoc iated with spatially concordant sites of positive ICS. AU PET activation fo ci with a t statistic less than 3.2 were associated with negative ICS. Conclusions. Positron emission tomography is an accurate method for mapping the primary somatosensory cortex before surgery. The need for ICS, which r equires local anesthesia, may be eliminated when PET foci with high (> 4.75 ) or low (< 3.20) t-statistic peaks are elicited by vibrotactile stimulatio n.