# Clinical impact of adherence to a standardized treatment algorithm for idiopathic sudden sensorineural hearing loss: a multicenter cohort study

## TL;DR

Following a standardized treatment plan for sudden hearing loss improves recovery, especially with early intravenous steroids and later targeted injections.

## Contribution

Demonstrates the clinical benefits of adhering to a standardized treatment algorithm for SSNHL in a real-world multicenter setting.

## Key findings

- Adherence to the treatment algorithm was associated with better hearing recovery (47.7% vs. 31.3%).
- Intravenous steroids improved early outcomes in severe cases, while intratympanic injections improved final recovery.
- Salvage intratympanic steroid therapy was independently linked to better recovery than observation.

## Abstract

Although systemic corticosteroids remain the mainstay of therapy for idiopathic sudden sensorineural hearing loss (SSNHL), evidence of adherence to standardized treatment algorithms and their impact on hearing outcomes is limited.

We conducted a retrospective analysis of a prospectively collected multicenter cohort comprising one university hospital, 16 affiliated hospitals, and two community clinics in Nagano Prefecture, Japan (2018–2024). Consecutive patients diagnosed with SSNHL were treated according to a unified algorithm derived from national epidemiological surveys. Adherence was defined as compliance with the initial and salvage therapies specified in the algorithm, and hearing outcomes were evaluated using the five-frequency pure-tone average (250–4,000 Hz) according to national criteria. Multivariable logistic regression with robust standard errors was used to identify determinants of adherence and factors associated with marked recovery (≥30 dB improvement).

The overall adherence rate was 60.3% among 373 patients. Non-adherence was more prevalent in severe cases (Grade ≥3), among older patients (≥65 years), individuals with diabetes, and secondary referrals. Adherent cases showed better final hearing recovery than non-adherent ones (47.7% vs. 31.3%, p < 0.01). In cases of Grade ≥3, intravenous steroid therapy during initial treatment yielded greater early improvement than oral therapy (Grade 3: 46.0% vs. 25.0%, p = 0.018); however, there was no significant difference in final outcomes. Of the 110 patients requiring salvage treatment, intratympanic steroid injection was performed in 51.8% and was independently associated with superior recovery vs. observation (adjusted odds ratio, 14.35; 95% confidence interval, 1.60–128.42; p = 0.017).

In this multicenter cohort, adherence to a standardized algorithm was moderate but was associated with improved hearing outcomes. In severe SSNHL, intravenous steroids enhance the early response—most notably in Grade 3—while salvage intratympanic steroid therapy considerably improves the final recovery rate. These findings support the implementation and optimization of the algorithm as well as the refinement of systemic dosing. Additionally, they highlight the importance of structured, guideline-based management in routine practice to improve outcomes in real-world SSNHL care.