Diagnostic accuracy of advanced imaging techniques for evaluation in patients with low grade gliomas

Abstract

Oligodendroglioma is the third most common glioma overall, accounting for 2%–5% of primary brain tumors and 5%–18% of all glial neoplasms. The tumor accounts for less than 1% of pediatric central nervous system neoplasms. According to the Central Brain Tumor Registry of the United States, oligodendrogliomas have an annual incidence of 0.3 per 100,000 people, while the tumor composed 4.2% of all primary brain tumors over a 25-year period in the Norwegian Cancer Registry. Oligodendrogliomas typically manifest as a round or oval sharply marginated mass involving the cortex or subcortical white matter at cross-sectional neuroimaging. MR imaging is superior to CT in defining the full extent of tumor involvement. The tumor is usually hypointense compared to gray matter on T1-weighted images and hyperintense compared to gray matter on T2-weighted images. Advanced MR imaging with the apparent diffusion coefficient (ADC) shows a characteristic but not pathognomonic difference between lowgrade and high-grade glial neoplasms. Lower ADC values, indicative of water restriction and likely reflective of lowered extracellular hyaluronic acid, are noted in high-grade tumors compared to the higher ADC values seen in low-grade tumors. Dynamic susceptibility-weighted contrast: the relative cerebral blood volume (CBV) measurements can be used to predict clinical response in patients with low-grade gliomas. MRSI is a method that measures chemical markers of neoplastic activity. Reduced NAA and increased Cho were found in all grade 2 glioma subtypes with a trend toward higher Cho in oligodendroglioma than in astrocytoma and oligoastrocytoma.