PT - JOURNAL ARTICLE AU - Nguyen, Sandy T. AU - Benson, John C. AU - Bathla, Girish AU - Farnsworth, Paul J. AU - Carlson, Matthew L. AU - Link, Michael J. AU - Lane, John I. TI - Peritumoral Hyperintense Signal on Postcontrast FLAIR Images Surrounding Vestibular Schwannomas Following Stereotactic Radiosurgery AID - 10.3174/ajnr.A8657 DP - 2025 Jun 05 TA - American Journal of Neuroradiology 4099 - http://www.ajnr.org/content/early/2025/06/05/ajnr.A8657.short 4100 - http://www.ajnr.org/content/early/2025/06/05/ajnr.A8657.full AB - BACKGROUND AND PURPOSE: Prior investigations have noted the presence of peritumoral hyperintense signal (a “halo”) around vestibular schwannomas on postcontrast 3D T2 FLAIR images. This study evaluated this phenomenon in a cohort of patients undergoing stereotactic radiosurgery.MATERIALS AND METHODS: A retrospective review was completed of consecutive patients with presumed vestibular schwannomas undergoing stereotactic radiosurgery. Tumor size, location, presence or absence of a peritumoral halo, and halo thickness were recorded. Images were reviewed for presence and size of peritumoral hyperintense signal on postcontrast 3D T2 FLAIR images before and after treatment.RESULTS: Twenty-six patients were included in this study, 14 of whom were women (54.0%). Average age was 62 ± 12 years. Before treatment, a postcontrast 3D T2 FLAIR hyperintense peritumoral halo was seen in 85% of patients, averaging 0.8 ± 0.4 mm in thickness. There was a higher incidence of peritumoral halo in posttreatment patients (96%) than pretreatment patients (85%) (P = .017) with a mean follow-up period of 1.2 years (SD 0.35) from November 12, 2019, to September 5, 2023. The average halo thickness was also larger in posttreatment patients (average =1.4 ± 0.4 mm) compared with pretreatment patients (0.8 ± 0.4 mm) (P < .001). Average tumoral size did not significantly change following treatment (P = .10).CONCLUSIONS: Vestibular schwannomas treated with stereotactic radiosurgery are more likely to have a peritumoral halo on postcontrast 3D T2 FLAIR images, with larger halo size as compared with pretreatment studies. Further study with a larger tumor cohort and longer follow-up will be necessary to determine if these findings are predictive of subsequent tumor shrinkage.CPAcerebellopontine angleIACinternal auditory canalSRSstereotactic radiosurgeryVSvestibular schwannoma