Comparative analysis of intraoperative MRI and early postoperative MRI findings in glioma surgery patients.

Objective: The extent of resection (EOR) is an important prognostic factor for both low- and high-grade gliomas. Intraoperative MRI (iMRI) has been used to increase the EOR in glioma surgery. While a recent study reported differences between iMRI and early postoperative MRI (epMRI), their specific relationship to postoperative clinical symptoms remains unclear. This study aims to compare the differences between iMRI and epMRI in glioma surgery.

Methods: A retrospective assessment was conducted on 43 patients with glioma who underwent surgery with iMRI and for whom no additional resection was performed after iMRI. The study evaluated the discrepancies in EOR, surgically induced contrast enhancement (SICE), and diffusion-weighted imaging (DWI) abnormality between iMRI and epMRI. EOR was defined as gross-total resection (GTR), near-total resection, subtotal resection (STR), or partial resection (PR) for enhancing lesions, and GTR, STR, or PR for nonenhancing lesions. In addition, the relationship between postoperative neurological findings and iMRI findings was evaluated.

Results: Discrepancies in EOR were observed in 2 (11.1%) of 18 cases with nonenhanced lesions and 1 (4.0%) of 25 cases with enhanced lesions. The positive rate of SICE was 25.0% on iMRI and 67.9% on epMRI. Enhancement at the resection cavity was the most frequent pattern in both iMRI and epMRI. The positive rate of enhancement of the resection cavity was strongly increased on epMRI compared with iMRI, potentially mimicking residual tumor. The positive rate of DWI abnormality was 73% on iMRI and 89.2% on epMRI. Among the 10 patients who showed no DWI abnormality on iMRI, 6 exhibited DWI abnormality on epMRI (the late-developing group). Two patients developed new neurological deficits postoperatively, and both showed DWI abnormality on both iMRI and epMRI. No patient in the late-developing group developed postoperative neurological deficits.

Conclusions: Overall, iMRI demonstrated more accurate EOR and less SICE compared with epMRI. Although the positive rate of DWI abnormality was lower on iMRI than on epMRI, the late-developing group showed no postoperative neurological deficits. Therefore, iMRI is more useful in assessing accurate EOR and detecting postoperative neurological deficits than epMRI.