Idiopathic Sudden Sensorineural Hearing Loss, But Not Compatible With the Classical Definition.

Background And Purpose:  The purpose of this study was to raise awareness for patients who did not meet the audiometric criteria of idiopathic sudden sensorineural hearing loss (SSNHL) but complained of acute hearing loss.

Materials And Methods: Medical records of patients who were diagnosed with SSNHL from October 2021 to March 2023 were examined retrospectively. Among 223 patients with SSNHL, 40 cases with atypical SSNHL and fitting in the criteria were included in the study. The patients who were included in this study were the ones who were given one bolus dose of IV systemic steroid (250 mg methylprednisolone with a proton pump inhibitor) and betahistine 2x24 mg po for a month. Pure tone audiometry was performed during the initial visit, on the fifth day, and at the end of the one-month usage of betahistine tablets. Hearing levels on the 250, 500, 1,000, 2,000, 4,000, and 8,000 Hz of the affected ear were compared with those of the contralateral ear. Hearing improvement was calculated as the hearing gain (in decibels) on the control audiograms and the resolution of the patients' complaints.

Results: These patients were suffering from idiopathic SSNHL with minimal hearing impairment. A total of 36 of the cases had hearing recovery on the fifth-day audiogram, and the remaining four patients showed hearing improvement on the first-month audiogram. The changes between the initial and the control audiogram values were found to be statistically significant (p<0.001). Additionally, these patients showed distinctive characteristics, such as being younger than the classical SSNHL population, lacking systemic diseases (diabetes or hypertension), and having good unaffected hearing.

Conclusion: Although there have been lots of studies to understand the pathophysiology, prognostic factors, and treatment options for SSNHL, atypical SSNHL patients have been underestimated and generally excluded from studies, and there have been a small number of studies on this issue. These patients might be accepted as having mild hearing loss. However, when the nerve injury is proven by audiograms, it is hard to decide what to do due to the lack of a treatment approach. This study is important as it focuses on atypical SSNHL cases. Further studies with larger group patients or prospective randomized-controlled group studies are needed to define these patients and decide how to treat this type of acute nerve dysfunction.