Auditory Disturbances and SARS-CoV-2 Infection: Brain Inflammation or Cochlear Affection? Systematic Review and Discussion of Potential Pathogenesis

Abstract

Patients affected by COVID-19 present a series of different symptoms; despite some of these are common, other less likely appear. Auditory symptoms seem to be less frequent, maybe because rarer or, alternatively, because they are underestimated during the clinical investigation. The hearing impairment might be related to the central or peripheral involvement of the auditory pathways; in particular, the likelihood of thrombosis might be one of the causes. To date, the prevalence of auditory symptoms such as sudden or progressive sensorineural hearing loss and tinnitus is unclear in COVID-19 patients. However, their presence might be an early sign of thrombosis or spread of the infection into the brain. In this systematic review of the literature we investigated the presence of auditory symptoms in COVID-19 patients and discussed their potential origin and causal relationship with SARS-CoV-2. Results showed that, despite rarely, auditory impairment can appear in patients with COVID-19 and should always be investigated for an early treatment and potential indicator of involvement of the central nervous system.

Olfactory Dysfunction, Headache, and Mental Clouding in Adults with Long-COVID-19: What Is the Link between Cognition and Olfaction? A Cross-Sectional Study

“…In this study, patients with headache suffered from severe and persistent smell disorders—we speculate [ 9 ], because the nasal mucosa was normal at the endoscopic investigation that it might be a sign of ongoing olfactory bulb inflammation [ 1 , 21 , 25 , 27 ]; however, due to inability of endoscopic investigation to detect micro-alteration of the mucosa at cellular level and the absence of MRI and biopsy of nasal bulb, the central involvement of the superior olfactory pathways can only be hypothesized.…”

“…Combined mental clouding and headache was strongly linked to increased severity of smell alterations (OR: 41), whereas patients with mental clouding alone had an OR of 19, and those with headache had an OR of 21. SARS-CoV-2-induced inflammation of the brain [ 23 ] may contribute to various Long-COVID symptoms, including vestibulocochlear impairment [ 1 ] and persistent cough [ 25 ]. Cognitive impairment and headache may both degrade an individual’s ability to correctly identifying the odors, as memory is necessary for odor recognition.…”

“…Initially considered primarily a respiratory illness, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is now recognized as a multi-organ disease. The infection, spreading from the nasopharynx into the brain [ 1 , 2 ], causes anosmia [ 3 ] and several neurologic symptoms [ 4 , 5 ], ranging from impaired executive function to hearing and vestibular dysfunction [ 1 ]. The respiratory infection and, when present, the olfactory and cognitive impairment tend to spontaneously dissipate within weeks following the infection [ 3 , 4 ], especially in patients with mild to moderate disease.…”

“…Persistence of neurologic symptoms is more common than initially recognized [ 1 , 4 , 5 ]. The propensity of SARS-CoV-2 to cause post-acute symptoms, such as fatigue, headache, altered memory/thinking, and joint pain or muscle aches, has led to coining of the term “Long-COVID Syndrome”, when symptoms persist over 6 months after swab negativization [ 6 ].…”

“…Mental clouding has been attributed to either selective neuronal mitochondrial dysfunction [ 11 ] or neuroinflammatory events, which arise following spread of the virus into the memory centers. The spread of the inflammation from the periphery to the olfactory bulbs and higher brain centers, has been observed in hearing and vestibular disorders [ 1 ]. Because cognitive and olfactory functions are interdependent [ 12 ], investigating the correlation between these entities could provide insights into a common pathway for the deficits that characterize Long-COVID Syndrome.…”