Perimetric visual field and functional MRI correlation: implications for image-guided surgery in occipital brain tumours

Objective-To compare the results of visual functional MRI with those of per imetric evaluation in patients with visual field defects and retrochiasmast ic tumours and in normal subjects without visual field defect. The potentia l clinical usefulness of visual functional MRI data during resective surger y was evaluated in patients with occipital lobe tumours. Methods-Eleven patients with various tumours and visual field defects and 1 2 normal subjects were studied by MRI using bimonocular or monocular repeti tive photic stimulation (8 Hz). The data obtained were analyzed with the st atistical parametric maps software (p<10(-8)) and were compared with the re sults of Goldmann visual field perimetric evaluation. In patients with occi pital brain tumours undergoing surgery, the functional data were registered in a frameless stereotactic device and the images fused into anatomical th ree standard planes and three dimensional reconstructions of the brain surf ace. Results-Two studies of patients were discarded, one because of head motion and the other because of badly followed instructions. On the remaining pati ents the functional activations found in the visual cortex were consistent with the results of perimetric evaluation in all but one of the patients an d all the normal subjects although the results of fMRI were highly dependen t on the choices of the analysis thresholds. Visual functional MRI image gu ided data were used in five patients with occipital brain tumours. No added postoperative functional field defect was detected. Conclusions-There was a good correspondence between fMRI data and the resul ts of perimetric evaluation although dependent on the analysis thresholds. Visual fMRI data registered into a frameless stereotactic device may be use ful in surgical planning and tumour removal.