**5. Etiology**

Although an etiological factor could be determined only in a small number of SHL patients, a wide spectrum of etiologic factors and diseases were blamed. Among these, infectious cause being in the first place, vascular causes, endothelial dysfunctions, hyperlipidemia, hypercoagulopathy, increased oxidative stress, autoimmunity, trauma, neurological disorders, endocrinopathies, iron deficiency anemia, neoplastic causes, paraneoplastic causes, and toxic causes are the most important factors. The most blamed causes in the SHL etiology are shown in **Table 1**. But it should be emphasized that none of these factors has been confirmed as a cause of SHL and idiosyncrasy is still the most common category in SHL (**Table 1**).


Atherosclerotic disorders Previous cardiopulmonary surgeries Arteriovenous malformations Acoustic trauma Aneurysm Erythrocyte Deformities **Neoplastic Causes Infection** Acoustic Schwannoma Viral Causes Multiple Myeloma Herpes viridea family (HSV Type 1, 2; VZV, CMV, EBV) Metastatic tumors Mumps Meningeal carcinomatosis Rubella Rubeola HIV **Endocrine Causes** Influenza family Hypothyroidism Enteroviridea family Iron deficiency anemia Adenovirus Diabetes mellitus Human Spumaretrovirus **Toxic Causes** Bacteria-Parasite Aminoglycosides *Treponema pallidum* Gold *Borrelia burgdorferi* Quinine *Toxoplasma gondii* Iron-containing drugs *Mycoplasma* spp. ACE inhibitors *Cryptococcus* spp. Loop Diuretics *Meningococci* Cisplatin *Enterobacteriae* Aspirin **Autoimmune Causes** Chemotherapeutic agents Autoimmune inner ear disease Phosphodiesterase Type-5 inhibitors Crohn's Disease Heroin Ulcerative Colitis Narcotic analgesics SLE Benzodiazepines Small vessel vasculitis **Neurological Causes** Cogan syndrome Multiple Sclerosis Antiphospholipid Antibody Syndrome **Psychiatric Causes** Sarcoidosis Histrionic (somatoform) deafness Endolymphatic hydrops **İdiosyncrasy** (most common cause)

**Table 1.** Etiology of sudden hearing loss.

**6. Medical history and physical examination**

Medical history is typical in SHL. Patients usually notice in the morning, during a telephone conversation, after exiting a noisy environment that their hearing sense is suddenly disappeared and generally they visit panicked the nearest physician with a fear of being deaf. In sudden hearing loss, as patients consult immediately a physician, early diagnosis and treatment are possible. During the physical examination, as no SHL-specific finding can be detected during the bilateral otomicroscopic examination, otoscopic examination is usually normal. In some cases, there can be an obstructive ear plug, which may be removed with difficulty. At the same time, in patients with otological disorders like chronic otitis media and tympanic membrane retraction, previous audiometry reports might be needed for the diagnosis and especially in patients with presbyacusis and missing audiometry reports, diagnosing is relatively difficult. In such cases, we have to depend only on the anamnesis. In the anamnesis, the important points are the presence of tinnitus and ringing, the presence of concomitant vertigo, and presence of a similar event in the past. Questioning of these aspects will provide useful information regarding the differential diagnosis. The patients should also be evaluated for the known chronic diseases and used medication. Especially autoimmune disorders, coagulation disorders, cardiovascular diseases, previous infectious diseases, and trauma should be questioned. Following the physical examination, hearing examination (Weber, Rinne) should be carried out in order to evaluate the type and severity of the hearing

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loss. Afterwards, the diagnosis should be confirmed with pure-tone audiometry.

The audiological examination is the most important process regarding the diagnosis. Puretone audiometry may enable a definitive diagnosis and also provide information about the severity of the hearing loss and the type of the audiological curve with additional data related to both differential diagnosis and prognosis. In addition to the pure-tone audiometry, tympanometric examination, acoustic reflex, speech audiometry may support the diagnosis. Such additional tests are not always needed. They are only recommended if there is a clinical necessity. In patients who cannot comply with the audiometry process ABR might be useful for the diagnosis. A definitive diagnosis of SHL can be made, if a hearing loss of 30 dB or greater is

As several different causes were suggested in respect of SHL etiology, the necessity of routine laboratory examination is still disputable regarding the diagnosis. The general consensus is that laboratory examination should be carried out only for the suspected etiological factors. If a viral involvement is suspected, viral antigen titration; if an autoimmune mechanism is

**7. Diagnosis**

**7.1. Audiology**

observed in three contiguous frequencies.

**7.2. Laboratory analysis**
