Tectal gliomas with “low-grade appearance”: natural history on MR imaging

Purpose Tectal gliomas (TGs) are often indolent, but heterogeneous study populations in prior cohorts yielded ambiguous results concerning their natural history. We analyzed the natural history of TGs with low-grade appearance on MR imaging. Methods We retrospectively analyzed TGs treated at our institution between 2010 and 2023. We included any space-occupying lesion of the tectum, excluding lesions with nodular contrast enhancement, cystic changes, or primarily pontine or mesencephalic involvement. Volumetric analysis was exclusively based on thin-sliced MRI sequences (≤ 2 mm). Primary outcome was tumor growth. Secondary outcome was relative annual growth rate (RGR). Results Twenty patients met the inclusion criteria (median age 22.5 years, interquartile range [IQR] 18.7–39.6). Headache was the most common indication for imaging (60%). Twelve patients (60%) required cerebrospinal fluid (CSF) diversion for hydrocephalus at the time of diagnosis. These patients did not all present with headaches upon first consultation. Median follow-up was 6.3 years (IQR 2.2–9.8). Median volumetric change from baseline to last follow-up was + 3.25% (IQR − 10.53 to + 28.47%), with a median RGR of 0.87%/year (IQR − 1.28 to 11.05%/year). Only one patient exhibited tumor growth with a marginal increase in size over 12.8 years of follow-up. Based on MR imaging findings, no malignant transformation occurred in our cohort Conclusion TG with a low-grade imaging phenotype show a predominantly stable long-term course. Management is typically limited to CSF diversion for hydrocephalus. Routine biopsy or tumor-directed therapy is not supported in the absence of concerning clinical or imaging features. MRI surveillance remains essential to detect rare progression.