LAUSR

We read with great interest the recent article by Bastos et al (1):” Challenges and Opportunities of Intraoperative 3D Ultrasound with Neuronavigation in Relation to Intraoperative MRI”. In this study, the authors reported their experiences using both 3D intraoperative ultrasound (iUS) and intraoperative MRI (iMRI) in 23 glioma surgeries. In 65% of patients, the tumors are located near the eloquent areas. 43% were recurrent cases. Three 3D iUS scans were routinely performed before and after dural opening and before the iMRI scan. More 3D iUS scans might be added if necessary. After tumor resection, one or two iMRI scans were performed to confirm the residual tumor. Multimodule neuro-navigation and electrophysiological monitoring techniques were also utilized during surgery. After surgery, 53% of patients achieved gross total resection. 21% of patients had temporary neurological deficits. None of them were permanent. In 82% of patients, the results of iUS were consistent with iMRI findings. While in the other four recurrent cases, the image quality of iUS was poor for the authors to decide. Three cases were presented in the paper. Case one was a small tumor located just before the precentral gyrus. IUS showed an apparent brain shift just after the dural opening. This information helped the surgeon choose the right site without causing injuries to the precentral gyrus. Case two was a giant left temporal glioma surrounded by bunches of fiber tracts. Multiple iUS scans were utilized to assess the resection process serially and helped the surgeon find the residual tumor. Case three was a low-grade glioma growing along the cingulate gyrus. 3D iUS helped the surgeon choose a safe corridor between functional areas and delineate the anatomical structures surrounding the tumor. The small residual tumor was found by iUS and confirmed by iMRI. The authors concluded that using 3D iUS in relation to iMRI had practical benefits for glioma surgeries and challenges. We agree with the authors’ opinion regarding the advantages and limitations of the iUS and iMRI. Combining these two techniques in glioma surgery seems reasonable and promising. Their conclusions are well supported by the data and illustrated cases. In addition to congratulating the authors, we would like to point out a few issues. The initial surgical treatment of glioma aims to obtain the maximal extent of resection (EOR) while preserving neurological function (2, 3). However, surgeon assessment of EOR based on visualization is prone to error, even when performed by experienced clinicians (4). Therefore, intraoperative imaging techniques such as iUS and iMRI were introduced into glioma surgery to achieve reliable resection control. iUS has been used in neurosurgery since the 1980s and is significantly correlated with preoperative MRI assessment of tumor volume (5–7). Mounting evidence also demonstrates the beneficial effects of ioUS for resection control in glioma surgery (8–10). The notable advantage of