Concurrent fibrous dysplasia is associated with a high incidence of cystic formation in vestibular schwannomas.

Background: Fibrous dysplasia (FD) is a rare hereditary bone disorder, typically accompanied by a seemingly-high percentage of cystic changes in central nerve system tumors. This study aimed to investigate the associations between concurrent FD lesions and the cystic formation of vestibular schwannoma (VS).

Methods: Patients with VSs in our institution from January 2020 to September 2022 were retrospectively included. Based on the contrasted MRI, VSs were grouped as the cystic and solid type. Concurrent FD was diagnosed based on the radiological findings. A logistic analysis was applied to investigate the relationship between concurrent FD and cystic VSs. The effect of the interaction between gender and concurrent FD on the cystic formation of VSs was further analyzed.

Results: The current study included 1255 patients with VSs (681 females with a median age of 47 years). Of them, 142 (11.3%) were with cystic VSs. A higher percentage of cystic VSs was observed in female patients (P = 0.021), patients with concurrent FDs (P < 0.001) and those with a larger VS volume (P < 0.001). An increasing trend in percentage of cystic VSs was found among patients with from 0 to ≥ 3 FD lesions (P for trend as < 0.001). A multivariate logistic analysis identified concurrent FD (odds ratio, 6.58; 95%CI, 1.66-26.09; P = 0.007) and VS volume (odds ratio, 1.55; 95%CI, 1.66-1.70; P < 0.001) as independent risk factors related to the cystic formation.

Conclusion: Concurrent FD is associated with a high incidence of cystic formation in VSs, which provides a new breakthrough point to investigate the underlying mechanism of cystic formation of VSs.