Diagnosis of Isocitrate Dehydrogenase-Mutant Astrocytoma in the Subcallosal Gyrus Using T2-Fluid-Attenuated Inversion Recovery Mismatch Sign and Quantitative Magnetic Resonance Relaxometry.

Astrocytoma, isocitrate dehydrogenase (IDH)-mutant, is one of the intraparenchymal brain tumors, strictly defined by its molecular characteristics. This tumor type is typically found in the frontal, insular, and temporal lobes. Patients harboring this type of tumor benefit the most from aggressive tumor removal compared to other low-grade appearing gliomas. Thus, accurate preoperative diagnosis is crucial in providing these patients with the most efficient and effective treatment strategy. This case study presents a 40-year-old male with an IDH-mutant astrocytoma in the subcallosal gyrus, an unusual location. The diagnosis was aided by the presence of the "T2-FLAIR (fluid-attenuated inversion recovery) mismatch sign," a key radiological feature of IDH-mutant astrocytomas, accompanied by magnetic resonance (MR) relaxometry that allows quantitative tissue characterization. This case highlights the importance of combining qualitative imaging features, such as the T2-FLAIR mismatch sign, with quantitative data, such as MR relaxometry, for accurate diagnosis, especially in cases with unusual tumor locations.