Abstracts

Rationale: It has been reported that several fibers connect between the ventrolateral frontal areas and temporoparietal areas, which take an important role in the special awareness and language function. However, the laterality of these pathways are still controversial. We investigate the laterality of this connection by means of cortico-cortical evoked potentials (CCEPs). The amplitudes and latencies of CCEP responses are compared between language dominant and non-dominant sides. Methods: From April 2014 to March 2016, 27 patients with intractable focal epilepsy, brain tumors and unruptured aneurysms who underwent the fronto-temporal craniotomy were enrolled in this study. All patients were right handed. The functional MRI or Wada test indicated that the language-dominant side was on the left hemisphere in all patients.The study population was composed of 14 male and 13 female patients (mean age: 45.1 years old, range: 13-73 years old), 17 language-dominant sides and 10 non-dominant sides.Under general anesthesia, subdural electrodes were placed on both frontal and temporo-parietal areas intraoperatively. Based on the neuronavigation, pars opercularis and trianglaris were anatomically identified. Thereafter, 1Hz alternating stimuli were delivered to these areas with the stimulus intensity of 10 mA. CCEPs were obtained from the temporo-parietal areas by averaging the electrocorticogram time-locked to the stimulus onset with MEE1232(Nihon Kohden Inc., Tokyo, Japan). The amplitudes and latencies of CCEP N1 components (early responses) were compared between the non-dominant group and the dominant group. For the statistical analysis, PASW (PASW statistics 17.0, SPSS Inc.) was used and the nonparametric Mann-Whitney U test was conducted. Results: The amplitudes of the CCEP N1 components were 60.2-750 μV in the language dominant sides (median 335.1 μV) and 55.1-634 μV in the non-dominant sides (median 125.65 μV).The amplitudes of the CCEP responses were significantly larger in the dominant hemispheres than the non-dominant sides (P=0.013 ( 0.05)). Conclusions: The CCEP amplitudes were significantly larger in the language dominant hemispheres.These findings would lead to better hypotheses regarding the relationship between language functions and development of the frontoparietal network. Funding: no