Quantitative MRI Assessment of Parenchymal Injury Following Transcallosal and Endoscopic Approaches to Third Ventricle Colloid Cysts

Background: Third ventricle colloid cysts (TVCCs) can result in obstructive hydrocephalus and acute neurological deterioration. Both the interhemispheric transcallosal approach (ITA) and endoscopic approach (EA) are established treatment strategies; however, their relative parenchymal impact on postoperative MRI, and the evolution of early to late imaging changes, remain poorly characterized. Objective: To compare early volumetric MRI findings following ITA and EA for TVCC resection and to determine whether early parenchymal injury persists on late imaging. Methods: A retrospective review was conducted of 23 patients (ITA, 13; EA, 10) who underwent both early and late postoperative MRI. Early T2/FLAIR hyperintensity volumes were segmented along the surgical tract; in EA cases, burr-hole tract volume was subtracted. Diffusion restriction was assessed with DWI/ADC. Late MRI was examined for gliosis, encephalomalacia, and parenchymal loss. Statistical analyses evaluated differences between approaches and correlations between early volumes and late outcomes. Results: Early hyperintensity volumes were significantly smaller after ITA compared with EA (349 ± 218 mm 3 vs. 2952 ± 2084 mm 3 ; p < 0.001). Diffusion restriction was observed in 7.7% of ITA versus 50% of EA cases (p = 0.052). On late MRI, gliosis, encephalomalacia, and parenchymal loss were absent in ITA but present in 50% of EA cases (p = 0.007 each). In EA, larger early volumes correlated with gliosis (p = 0.032), encephalomalacia, and parenchymal loss (p = 0.016 each). Gross total resection was achieved in 92% of ITA versus 50% of EA cases (p = 0.039). Conclusion: Compared with ITA, EA was associated with larger early parenchymal injury, half of which persisted as structural abnormalities on late imaging, indicating an increased risk of lasting tissue damage. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany