Real-Time Motor Cortex Mapping for the Safe Resection of Glioma: An Intraoperative Resting-State fMRI Study

Abstract

Background and purpose: Resting-state functional MR imaging has been used for motor mapping in presurgical planning but never used intraoperatively. This study aimed to investigate the feasibility of applying intraoperative resting-state functional MR imaging for the safe resection of gliomas using real-time motor cortex mapping during an operation.

Materials and methods: Using interventional MR imaging, we conducted preoperative and intraoperative resting-state intrinsic functional connectivity analyses of the motor cortex in 30 patients with brain tumors. Factors that may influence intraoperative imaging quality, including anesthesia type (general or awake anesthesia) and tumor cavity (filled with normal saline or not), were studied to investigate image quality. Additionally, direct cortical stimulation was used to validate the accuracy of intraoperative resting-state fMRI in mapping the motor cortex.

Results: Preoperative and intraoperative resting-state fMRI scans were acquired for all patients. Fourteen patients who successfully completed both sufficient intraoperative resting-state fMRI and direct cortical stimulation were used for further analysis of sensitivity and specificity. Compared with those subjected to direct cortical stimulation, the sensitivity and specificity of intraoperative resting-state fMRI in localizing the motor area were 61.7% and 93.7%, respectively. The image quality of intraoperative resting-state fMRI was better when the tumor cavity was filled with normal saline (P = .049). However, no significant difference between the anesthesia types was observed (P = .102).

Conclusions: This study demonstrates the feasibility of using intraoperative resting-state fMRI for real-time localization of functional areas during a neurologic operation. The findings suggest that using intraoperative resting-state fMRI can avoid the risk of intraoperative seizures due to direct cortical stimulation and may provide neurosurgeons with valuable information to facilitate the safe resection of gliomas.

Fig 1.

Validation of iR-fMRI with DCS. A, The pR-fMRI scan shows the motor cortex located posterior to the tumor. B, DCS locates positive sites in the hand area (H) and positive sites in the mouth area (M). The green and blue dots in A represent the positive sites in the hand and mouth areas, respectively, located by intraoperative DCS. C, iR-fMRI reveals that the motor cortex is behind the tumor cavity. D, Intact motor cortex after tumor resection. The green and blue dots represent the positive sites in the hand and mouth areas, respectively, located by intraoperative DCS. Pre-op indicates preoperative; Post-op, postoperative; L, left; R, right.

Fig 2.

Procedure for iR-fMRI- and DCS-assisted tumor resection. A, pR-fMRI scan reveals that the motor cortex is located behind the left frontal lesion. B, Direct cortical stimulation locates 2 positive sites in the hand area (H), 1 positive site in the foot area (L), and 2 positive sites in the language area (1 and 2). C, The iR-fMRI scan displays the motor cortex behind the tumor cavity at a distance from the tumor residue (green arrow). D, Intraoperative MR image suggests a small amount of tumor residue closer to the deep motor area behind the tumor cavity (green arrow). E, The final iR-fMRI scan shows that the motor cortex located behind the tumor cavity is well-protected. F, The final MR imaging scan reveals complete tumor resection. L indicates left; R, right.