Inner Ear Schwannomas as a Risk Factor for Early Hearing Loss Independent of Vestibular Schwannoma Growth in NF2 -related Schwannomatosis.

OBJECTIVE

To determine whether the presence of an inner ear schwannoma (IES) is associated with earlier hearing loss, and whether this effect is independent of vestibular schwannoma size or growth in patients with NF2 -related schwannomatosis ( NF2 -SWN).

STUDY

DESIGN

Retrospective cohort study.

SETTING

Quaternary NF2 -SWN center.

PATIENTS: Three hundred seventy-three ears, including 316 with VS only and 57 with VS and IES.

MAIN OUTCOME MEASURES: Primary outcomes: (1) Age at loss of normal hearing (timepoint 1; TP1); (2) Age at loss of serviceable hearing (timepoint 2; TP2). Secondary exploratory objectives: (1) VS size and growth rate at each timepoint; (2) IES size and location.

RESULTS

Mean age at loss of normal hearing was 39 years in ears with VS only and 25 years in ears with VS + IES ( P = 0.00015). Mean age at loss of serviceable hearing was 42 years in ears with VS only and 29 years in ears with VS + IES ( P = 0.00020). Kaplan-Meier analyses demonstrated significantly earlier deterioration in ears with IES at both timepoints ( P < 0.0001). At TP1, logistic regression showed that although ears with IES lost normal hearing at a younger age, this association was not independent of VS size. At TP2, however, both unadjusted analyses and Firth-penalized logistic regression demonstrated that IES and smaller VS size were independently associated with earlier loss of serviceable hearing. A Cox proportional hazards model assessing progression from TP1 to TP2 further showed that IES status and VS size at TP1 were independent predictors of faster progression (adjusted hazard ratio for IES 2.79, 95% CI: 1.50-5.19). There was no significant difference in hearing outcomes between intracochlear and non-cochlear IES.

CONCLUSIONS

IES is associated with earlier hearing loss, particularly with respect to loss of serviceable hearing. These findings suggest that patients with both a VS and an IES may experience hearing decline at younger ages and at smaller VS sizes than those with VS alone. This information may inform clinical decision-making and guide timing of interventions in NF2 -SWN.