Enhanced intraoperative visualization of the optic chiasm using contrast-enhanced balanced steady-state free precession imaging during endoscopic transsphenoidal surgery

Preoperative balanced steady-state free precession (bSSFP) imaging is helpful in endoscopic transsphenoidal surgery (ETSS) for accurately evaluating the optic chiasm and surrounding structures. While intraoperative magnetic resonance imaging (iMRI) has been shown to improve surgical outcomes, the utility of intraoperative contrast-enhanced bSSFP remains underexplored. This study was performed to assess the effectiveness of intraoperative contrast-enhanced bSSFP compared with T2-weighted imaging (T2WI) for visualizing the optic chiasm and to identify factors affecting image quality. This retrospective study included patients who underwent ETSS between March 2015 and March 2020, with both preoperative and intraoperative MRI, including coronal contrast-enhanced bSSFP and T2WI sequences. Two neurosurgeons independently scored optic chiasm visibility using a 4-point scale (0-3). Statistical analyses involved paired comparisons of imaging scores and assessments of factors influencing intraoperative contrast-enhanced bSSFP quality, such as intracranial air and blood in the tumor cavity.Eighteen cases were analyzed. Contrast-enhanced bSSFP scores were significantly higher than T2WI scores for both preoperative imaging (median 3.0, IQR 2.75-3.0 vs. median 2.0, IQR 1.0-2.0; p = 0.0002) and intraoperative imaging (median 3.0, IQR 2.0-3.0 vs. median 2.0, IQR 1.0-2.0; p = 0.0002). A decrease in intraoperative contrast-enhanced bSSFP scores was observed in 5 cases and was significantly associated with intracranial air (p = 0.047) but not with blood in the tumor cavity (p = 0.608). Intraoperative contrast-enhanced bSSFP was superior to T2WI for optic chiasm visualization, consistent with preoperative findings. However, intracranial air significantly degraded the image quality of contrast-enhanced bSSFP.