Idiopathic Sudden Sensorineural Hearing Loss in Sweden : Diagnostic Protocol and Treatment in Relation to Outcome

Abstract: Idiopathic Sudden Sensorineural Hearing Loss (ISSNHL) is a rapid loss of hearing caused by damage to the cochlea (inner ear) or auditory nerve. Spontaneous recovery has been seen in 32% - 81%. The incidence of the ISSNHL has been estimated to be between 5 and 20 per 100,000 per year. Different theories (infections, vascular catastrophes, immunologic damage or intracochlear membrane break) about the etiology have resulted in different treatment policies. The effect of therapy is difficult to evaluate for a single physician who sees just a few patients annually.The aim of the present thesis was to analyze the management and treatment of ISSNHL patients in Sweden with regard to outcome.A national database was developed for Sweden with half of all ENT clinics in Sweden participating by submitting a questionnaire for each patient with SSNHL. The questionnaire covered the patient’s background, current disorder, past and family history of different diseases, examinations and treatment. Audiograms at the onset of SSNHL and after three months were requested.All results were analyzed using ordinal logistic regression looking for interactions with hearing recovery and remaining hearing loss as dependent variables. Independent of treatment or no therapy heredity for hearing loss (I, II), older age (I, II) and presence of vertigo (II) was significantly associated with negative outcome. 40% of all patients had an MRI or CT, where 3 – 4% had acoustic neuroma. 24% of patients with ISSNHL who had hematological tests taken had one or more pathological findings. Blood screening varied from simple routine tests to a complete analysis with such tests as HSP70, Anti-Neutrophilic Cytoplasmic Antibodies (ANCA) and Borrelia tests. There was no association between any of these laboratory tests and either hearing improvement or remaining hearing loss evaluating the tests separately (I, II) or after categorization in comparison with those who had normal laboratory findings (II). Patients with hearing loss in the mid-frequency region had significantly better odds for hearing improvement compared to the other three frequency regions (low, high and “flat loss”). Almost 60% of patients with ISSNHL were medically treated, of which nearly 90% got corticosteroids. The medication had no association with either hearing improvement or remaining hearing loss. However, patients who were prescribed rest or sick leave had higher odds for hearing improvement regardless of other treatment. Those patients who did not receive any treatment at all also came significantly later to the ENT clinics than those treated medically and consequently had worse prognosis.Conclusion: There is no standard program for management or treatment of ISSNHL in Sweden. The diagnostic protocol varies. MRI is an underused resource to get specific diagnoses for the condition especially acoustic neuromas. Regardless of pathological findings, treatment is mainly limited to corticosteroids or no medication with no difference in outcome. A randomized placebo controlled study is necessary to evaluate whether there is an effect of corticosteroids on ISSNHL.