Factors Associated With Bilateral Involvement in Non-Infectious Labyrinthitis: A Case-Control Study.

BACKGROUND: Non-infectious labyrinthitis (NIL) is an inflammatory disorder of the inner ear characterized by cochlear and vestibular symptoms associated with impairment of the blood-labyrinth barrier on delayed FLAIR MRI. Although the condition may initially present unilaterally, some patients subsequently develop bilateral disease, which can lead to greater functional disability. Identifying factors associated with bilateralization (i.e., progression from unilateral to bilateral involvement) remains clinically important. METHODS: We conducted a retrospective case-control study in a tertiary referral center to identify factors associated with bilateral involvement in NIL. Fifty patients diagnosed with NIL between 2018 and 2025 were included: 25 with bilateral NIL (BNIL) and 25 with unilateral NIL (UNIL). Clinical, audiometric, vestibular, and biological data were collected from medical records. Logistic regression analyses were performed to identify factors associated with bilateralization. RESULTS: Compared with UNIL patients, BNIL patients were significantly younger (42.4 ± 10.9 vs. 54.8 ± 11.6 years, p = 0.0003) and more frequently female (60% vs. 24%, OR = 4.75, p = 0.010). Systemic disease was more frequent in BNIL patients (36% vs. 4.0%, OR = 13.50, p = 0.011). In multivariate analysis, younger age, female gender, and the presence of systemic disease were independently associated with bilateral involvement. CONCLUSIONS: Younger age, being female, and systemic disease are associated with bilateralization in NIL. These findings may help identify subgroups who warrant closer clinical monitoring. However, given the retrospective case-control design, small single-center sample, referral bias, and sparse data (particularly for systemic disease), these results should be interpreted as exploratory associations and hypothesis-generating rather than definitive prognostic predictors ready for clinical risk scoring.