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Background
Sudden, sensorineural hearing loss (SSHL) is an acute, mostly unilateral dysfunction of the inner ear that is characterized by sudden onset and potential progression to complete deafness. Elderly people are primarily affected, but, it can occur at every age. While the estimated incidence is 10-20/100.000/year, the true incidence is probably much higher since it increases in industrialized countries and many cases are often misdiagnosed or regarded as age-related unavoidable fate [1-3]. Hearing impairment can be accompanied by tinnitus, ear fullness and/or vertigo [4]. The etiology of SSHL is mostly unknown and is therefore often referred to as idiopathic. Less than one third of all cases can be definitely attributed to haemorheological disturbances or viral infections, and less common to autoimmunological mechanisms [1, 4-8]. While some experimental and clinical trials could link classical cardiovascular risk factors to the development and outcome of SSHL, others could not [9-14]. Clinically, according to pure-tone audiometry, SSHL can either affect only the low, the high, or the medium frequencies, or it can affect all frequencies (pancochlear) with varying degrees up to deafness. Each of these forms may represent a distinct underlying entity [5, 15]. In individual cases of pancochlear hearing loss a perilymph fistula (PLF) may play an etiological role. A PLF can be caused by external or internal factors (e.g., head injury, scuba diving, lifting) which lead to a relative change in ambient, middle ear, or intracranial pressure, or it can occur spontaneously [16-18]. Patients with PLF mostly present with hearing loss, vertigo, tinnitus and subjective and/or objective fistula symptoms (e.g. subjective disequilibrium/nystagmus when positive or negative pressure is applied to the external ear).
In general, no effective treatment option is available for the majority of SSHL patients and many patients do not completely recover. The most important innovations in SSHL therapy in the last few decades are apheresis of fibrinogen and low density lipoproteins (LDL) and administration of steroids via intratympanic routes [19, 20]. New treatment options are urgently needed since the effectiveness of steroids (oral or systemic) in the treatment of SSHL remains unproven [21-23].
The outcome of SSHL, especially the idiopathic form, is not predictable. In the last few decades, numerous studies have attempted to establish a relationship between certain accompanying symptoms or findings, e.g....