The use of advanced neuroimaging modalities in the evaluation of low-grade glioma in adults: a literature review

Low-grade gliomas encompass a subgroup of cancerous glial cell growths within the central nervous system and are distinguished by their slow growth and relatively low malignant potential. Despite their less aggressive nature, these tumors can still cause significant neurological symptoms through the compression of surrounding neural and vascular structures and, in some instances, undergo malignant transformation. For these reasons, timely and appropriate evaluation and management of low-grade gliomas is critical. Medical imaging stands as a cornerstone for evaluating patients with lowgrade gliomas because of its noninvasive nature and ability to provide a vast amount of information about the underlying lesion. With the growing number of neuroimaging techniques and their capabilities, there is a lack of clear guidance on which techniques to utilize for the assessment of low-grade gliomas and what their respective core use cases should be. In this literature review, the authors discuss in significant depth the available evidence pertaining to the use of advanced neuroimaging techniques in the evaluation and management of low-grade gliomas. Specifically, they review the specific- ity, sensitivity, accuracy, and use cases of magnetic resonance spectroscopy (MRS), perfusion MR imaging (perfusion MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), positron emission tomography (PET), single -photon emission computed tomography (SPECT), as well as other emerging imaging techniques. They conclude that most of the advanced neuroimaging techniques are reliable in differentiating lowfrom high-grade gliomas, whereas MRS and DTI may further support molecular subclassification of the tumor. PET has been best employed for the purpose of tumor biopsy, whereas fMRI and DTI can be particularly valuable in preoperative surgical planning, as they delineate the functionally eloquent brain regions that need to be preserved during tumor resection. MRS, PET, SPECT, and perfusion MRI are best suited to monitor tumor progression, as their respective metrics closely correlate with the underlying metabolic activity of the tumor. Together, these techniques offer a vast amount of information and serve as tools for neurologists and neurosurgeons managing patients with low-grade gliomas.