Timing of Hyperbaric Oxygen Therapy in Idiopathic Sudden Sensorineural Hearing Loss

Background: To evaluate the efficacy of hyperbaric oxygen therapy (HBOT) in the treatment of idiopathic sudden sensorineural hearing loss (ISSNHL), with particular emphasis on the impact of treatment initiation timing. Methods: This retrospective study included 127 patients with ISSNHL who received HBOT at the Ankara Etlik City Hospital, between February 2023 and August 2024. Patients were categorized into 3 groups based on treatment initiation time: Group 1 (0-14 days), Group 2 (15-30 days), and Group 3 (>30 days). Hearing outcomes were evaluated using pure-tone average at 4 frequencies and word recognition scores, according to the American Academy of Otolaryngology–Head and Neck Surgery Foundation criteria. Results: Of the 193 patients initially screened, 127 met inclusion criteria. The last complete recovery was observed in a patient who began HBOT on day 26, and the last partial recovery occurred at day 48. No improvement was seen in patients who started treatment beyond 48 days. Receiver-operating characteristic analysis identified day 18 as the cut-off for complete recovery and day 19 for partial/slight recovery. Conclusion: Hyperbaric oxygen therapy was associated with greater improvement when initiated within the first 3 weeks, particularly before day 19. However, meaningful improvements may still occur in selected patients even after 30 days, suggesting that HBOT should not be dismissed as a treatment option for late presenters. Early initiation remains critical, and prospective controlled trials are warranted to further clarify the true efficacy of HBOT in the late period.