Sudden hearing loss: a medical emergency

Concerns regarding a sudden change in hearing are common. They may be caused by a simple conductive hearing loss due to earwax impaction. However, they can also be caused by sudden sensorineural hearing loss (SSNHL), a condition that requires prompt recognition and management for better chances of recovery (Kuhn et al., 2011; Chandrasekhar et al., 2019; Doo et al., 2020).

According to the National Institute on Deafness and Other Communication Disorders (NIDCD) in the USA, SSNHL is defined as a hearing loss that is sensorineural in nature. It occurs within a 72-hour window, affecting at least three consecutive frequencies with a decrease of > 30 dB HL. This decrease is usually confirmed by comparing hearing thresholds between ears, as the vast majority of cases are unilateral. The hearing loss might also be accompanied by tinnitus and/or vertigo in some cases. In the USA, the incidence is 5 to 27 per 100.000 (Chandrasekhar et al., 2019).

A physical examination followed by a hearing assessment (pure tone audiometry and tympanometry) can distinguish external and middle ear conditions from SSNHL. The confirmation of the SSNHL should be followed by an urgent ENT referral for immediate etiological investigation and management (NICE guidelines, 2018).

Several different etiologies can be related to SSNHL (Kuhn et al., 2011), including neurologic conditions such as multiple sclerosis (Di Stadio et al., 2018), otologic conditions such as Meniere’s disease, neoplastic such as vestibular schwannoma (Wasano et al., 2021), traumatic, autoimmune, vascular such as cerebrovascular accident/stroke or even infectious, such as bacterial meningitis. Despite that, in most cases, the SSNHL is classified as idiopathic, as the exact pathophysiology of the condition remains unknown.

The recovery prognosis will depend on several factors, such as age, degree of hearing loss, presence of concomitant symptoms (vertigo), and the time between the onset of hearing loss and treatment (Chandrasekhar et al., 2019). Research indicates that approximately one-third to two-thirds of patients with SSNHL may have a partial recovery of hearing loss within two weeks. Patients with no significant hearing change within two weeks have a worse prognosis.

The emergence of COVID-19 infection has also brought SSNHL into focus, as several recent papers have described cases of SSNHL following COVID-19 infection (Kilic et al., 2020; Koumpa et al., 2020; Lang et al., 2020). Koumpa et al. (2020), for instance, reported one case in the UK involving a 45-year-old patient who had been treated in the hospital for COVID-19 and developed, at the same time, a unilateral SSNHL. The hearing test confirmed a unilateral moderate to severe hearing loss that was partially recovered after a series of intratympanic steroid injections. Lang et al. (2020) also described a similar case involving a 30-year-old staff nurse who developed classic COVID-19 symptoms, followed by a sudden right-sided hearing loss (confirmed by audiogram) and tinnitus. Despite that, in a recent systematic review, Almufarrij and Munro (2020) discussed the quality of those studies as most of them are only case reports with no comprehensive assessment.

Regardless of the cause, the important message here is about considering any sudden hearing issue as a medical emergency. Immediate medical attention is crucial, and delaying it could have serious consequences.

References:

- Kuhn M, Heman-Ackah SE, Shaikh JA, Roehm PC. Sudden sensorineural hearing loss: a review of diagnosis, treatment, and prognosis. Trends Amplif. 2011Sep;15(3):91-105.

- Doo JG, Kim D, Kim Y, Yoo MC, Kim SS, Ryu J, Yeo SG. Biomarkers Suggesting Favorable Prognostic Outcomes in Sudden Sensorineural Hearing Loss. Int J Mol Sci. 2020 Sep 30;21(19):7248

- Chandrasekhar SS, Tsai Do BS, Schwartz SR, Bontempo LJ, Faucett EA, Finestone SA, Hollingsworth DB, Kelley DM, Kmucha ST, Moonis G, Poling GL, Roberts JK, Stachler RJ, Zeitler DM, Corrigan MD, Nnacheta LC, Satterfield L. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg. 2019 Aug;161(1_suppl)

- Hearing loss in adults: assessment and management. NICE guideline, 21 Jun 2018

- Wasano K, Oishi N, Noguchi M, Hentona K, Shinden S, Kitama T, Tsuzuki N, Kawasaki T, Hiraga Y, Takei Y, Ogawa K. Sudden sensorineural hearing loss in patients with vestibular schwannoma. Sci Rep. 2021 Jan 21;11(1):1624.

- Di Stadio A, Dipietro L, Ralli M, Meneghello F, Minni A, Greco A, Stabile MR, Bernitsas E. Sudden hearing loss as an early detector of multiple sclerosis: a systematic review. Eur Rev Med Pharmacol Sci. 2018 Jul;22(14):4611-4624.

- Kilic O, Kalcioglu MT, Cag Y, Tuysuz O, Pektas E, Caskurlu H, Cetın F. Could sudden sensorineural hearing loss be the sole manifestation of COVID-19? An investigation into SARS-COV-2 in the etiology of sudden sensorineural hearing loss. Int J Infect Dis. 2020 Aug;97:208-211.

- Koumpa FS, Forde CT, Manjaly JG. Sudden irreversible hearing loss post COVID-19. BMJ Case Rep. 2020 Oct 13;13(11):e238419.

- Almufarrij I, Munro KJ. One year on: an updated systematic review of SARS-CoV-2, COVID-19 and audio-vestibular symptoms. Int J Audiol. 2021 Mar 22:1-11.

- Lang B, Hintze J, Conlon B. Coronavirus disease 2019 and sudden sensorineural hearing loss. J Laryngol Otol. 2020 Oct 1:1-3. doi: 10.1017/S0022215120002145.