Αθανάσιος Μπίμπας, Αναπληρωτής Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Ιωάννης Σέγγας, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Ευθύμιος Κυροδήμος, Επίκουρος Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ
Introduction: Idiopathic Sudden Sensorineural Hearing Loss (ISSHL) is defined as a hearing loss of more than 30dB that occurs in at least 3 consecutive frequencies, within 3 days and despite necessary and proper diagnostic management no cause can be identified. ISSHL is a common otologic emergency, presenting as an acute hearing loss with an abrupt occurrence. The incidence is estimated to be approximately 10-30 cases per 100,000/person/year, but it is believed to be greater, since this is only the statistics for patients who sought treatment. A variety of causes have been proposed, including viral infections, vascular occlusion, immunological disorders, labyrinthine membrane rupture, blood disorders, metabolic conditions, and activation of cochlear nuclear factor kappa B, but each has its own weaknesses, and none of them can fully explain the underlying pathogenesis. Therefore, the real origins for ISSHL still remain controversial. A biomarker can be defined as a characteristic that is objectively measured and evaluated as an indication of normal biologic processes, pathogenic processes, or response to a therapeutic intervention.
Methods: A systematic search was conducted in PubMed and Google Scholar databases with combinations of the following keywords: “idiopathic sudden sensorineural hearing loss”, “sudden sensorineural deafness”, “sudden sensorineural hearing loss”, “clinical outcome”, “biomarker”, “prognosis”, “prognostic factor”. The articles’ inclusion period was from 2010 and search was limited to English language.
Results: A total of 539 papers were found with the MeSH terms used. A second more specific and narrow search identified 40 articles that were carefully reviewed. Their references were also reviewed for a further comprehensive search.
Discussion: Most of the biomarkers suggested in the literature are direct or indirect products, molecules and diagnostic tests that attempt to explain the potential underlying mechanisms of ISSHL. Such proposed biomarkers are: micro-RNAs, various inflammation markers of complete blood count, procalcitonin, calprotectin, prestin, various markers of oxidative stress, blood lipid markers, enzymes such as homocysteine, fibrinogen, folic acid and finally of increased value seems to be the role of certain Magnetic Resonance Imaging sequences and protocols.
Conclusions: Most of the studies and meta-analyses show robust evidence to support the use of these specific biomarkers for the prognosis of ISSHL. However, almost all of the papers in their conclusions state that more studies are needed to enable the findings to be consistent and to be used in daily clinical practice. Until then, some of the biomarkers (being cheap and fast) can be evaluated in almost every case of ISSHL, others seem to have their place in specific patient categories (patients with cardiovascular diseases or with profound hearing loss or deafness), and others, for the time being, can only be used in research protocols, the latter being the most promising that eventually will be the most effective in the prognosis but also in the interpretation of pathogenesis of ISSHL. Due to the incidence of the disease and the significant impact on the person with hearing loss, the identification of biomarkers and potentially modifiable risk factors for this condition should be a priority of the health system.