Peritumoral Hyperintense Signal on Postcontrast FLAIR Images Surrounding Vestibular Schwannomas following Stereotactic Radiosurgery.

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%) ( = .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) ( < .001). Average tumoral size did not significantly change following treatment ( = .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.