**2. Epidemiology**

Although SHL constitutes approx. 1% of all sensorineural hearing losses, its incidence changes between 5 and 20/100,000 in different sources [2]. However, high rates such as 160/100,000 had also been reported in the literature and 40,000 new cases were diagnosed every year in the USA [3]. The incidence and prevalence of SHL are probably slightly higher than the calculated values, because of the rapid development of SHL and the high rate of spontaneous regression. Many studies reported that SHL had no correlation with gender and that the female/male ratio was equal or insignificantly different. In this regard, it seems safe to say that gender is not a risk factor. Similarly, no significant left/right ear distinction was detected. Although SHL is usually unilateral, bilateral involvement is emerging in a small percentage of patients (1–2%) [4]. Nevertheless, bilateral SHL is a more serious condition compared to the unilateral form and is often related to systemic disorders and has a relatively worse prognosis [5, 6].
