The cortical high-flow sign in oligodendroglioma, IDH-mutant and 1p/19q-codeleted is correlated with histological cortical vascular density.

Background and purpose: The cortical high-flow sign has been more commonly reported in oligodendroglioma, IDH-mutant and 1p/19q-codeleted (ODG IDHm-codel) compared to diffuse glioma with IDH-wildtype or astrocytoma, IDH-mutant. Besides tumor types, higher grades of glioma might also contribute to the cortical high flow. Therefore, we investigated whether the histological cortical vascular density or CNS WHO grade was associated with the cortical high-flow sign in patients with ODG IDHm-codel.

Materials and methods: This retrospective study consisted of pathologically confirmed 25 adult patients with ODG IDHm-codel. We implemented pseudo-continuous arterial spin labeling technique with background suppression. Subtraction images were generated from paired control and label images. Tumor-affecting cortices without intense contrast enhancement on conventional MR imaging were targeted for the determination of the cortical high-flow sign. Immunohistochemical staining of CD31 antibody was performed for the identification of vascular endothelial cells. A microscopic field of the most intense vascularization was captured in each specimen. The vessel number and the relative vascular density (%Vessel) were compared between the positive cortical high-flow sign (CHFS⁺) and the negative cortical high-flow sign (CHFS^-) groups using the Mann-Whitney U test. Second, Fisher's exact test was used to compare the difference between the presence or absence of cortical high-flow sign and CNS WHO grades. Finally, the vessel number and %Vessel were compared between the CNS WHO grade 2 and grade 3 using the Mann-Whitney U test.

Results: The vessel number and %Vessel were higher in patients with the CHFS⁺ group than in patients with CHFS^- group (p = 0.016 and p = 0.005, respectively). We observed no significant differences (p = 1.00) in the frequency of cortical high-flow sign between the CNS WHO grade 2 and grade 3. In addition, no significant differences are found in the vessel number and %Vessel between the CNS WHO grade 2 and grade 3 (p = 0.121 and p = 0.475, respectively).

Conclusion: The cortical high-flow sign on ASL, which is more commonly found in ODG IDHm-codel than in diffuse glioma with IDH-wildtype or astrocytoma, is associated with the histological cortical vascular density in patients with ODG IDHm-codel.