Application of language blood oxygenation level dependent functional MRI in the navigating operation of neurosurgery

Objective To verify the accuracy of blood oxygenation level dependent (BOLD)-based activation using electrocortical stimulation mapping (ESM) and explore the value of language fMRI in the navigating operation of neurosurgery. Methods In 8 cases with brain tumors,BOLD-fMRI examinations were done before the operations. Under the state of awake anesthesia,the patients were aroused and ESM was conducted. Point-to-point comparison between the BOLD signal activations and the ESM was carried out under the surveillance of the neuro-navigation technology. In order to observe the sensibility and specificity of BOLD activations, the location of BOLD activations and the point of ESM was compared to calculate the stimulating positive points inside the regions of BOLD signals(real positive), outside BOLD regions(pseudo-negative), the stimulating negative points inside the regions of BOLD signals(pseudo-positive), and outside BOLD region(real negative). Two kinds of criteria for assessment were used. One was that the positive stimulating points were located in BOLD regions, and the other was that the positive stimulating points were located within 1 cm around the range of BOLD regions. Removal of the lesions were conducted with the tissue 1 cm around the language region preserved, and the cortex inside 0.5-1.0 cm distance from the positive points were retained. Results Of the 8 cases, only 6 finished the tasks. Among them, 3 cases were with astrocytoma of grade 2,2 were with astrocytoma of grade 3, and one with glioblastoma. The total number of stimulating points was 48, among which the positive points were 11. When the first criteria was applied, the sensitivity was 72.7% (8/11), and the specificity was 81.8% (30/37). When the second criteria was applied, the sensitivity was 82.0% (9/11),and the specificity was 75.6% (28/37). Follow-up after operation showed no aphasia occurred. Conclusions BOLD-fMRI had a high sensitivity and specificity in displaying the language regions. But due to the great variation of brain language area among the people, we need more studies of large sample to obtain enough experience before it can be used clinically. Key words: Magnetic resonance imaging;  Transcutaneous electric nerve stimulation; Neuronavigation;  Anesthesia