Anosmia in COVID-19 Associated with Injury to the Olfactory Bulbs Evident on MRI

Abstract

Patients with coronavirus disease 2019 (COVID-19) may have symptoms of anosmia or partial loss of the sense of smell, often accompanied by changes in taste. We report 5 cases (3 with anosmia) of adult patients with COVID-19 in whom injury to the olfactory bulbs was interpreted as microbleeding or abnormal enhancement on MR imaging. The patients had persistent headache (n ¼ 4) or motor deficits (n ¼ 1). This olfactory bulb injury may be the mechanism by which the Severe Acute Respiratory Syndrome coronavirus 2 causes olfactory dysfunction. ABBREVIATIONS: COVID-19 ¼ coronavirus disease 2019; SARS-CoV-2 ¼ Severe Acute Respiratory Syndrome coronavirus 2 C oronavirus has the human respiratory system as its main target but also has neuroinvasive capabilities and can spread from the respiratory tract to the CNS. 1-3 Therefore, patients with coronavirus disease 19 (COVID-19) may present with neurologic symptomatology with repercussions on imaging examinations, 4-18 and these have been described in association with ischemic infarct, 8,9 hemorrhage, 11 acute hemorrhagic necrotizing encephalopathy, 10 cerebral venous thrombosis, 13 and diffuse leukoencephalopathy with microhemorrhage. 15 Transmission from person to person occurs mainly by direct contact or droplets spread by coughing or sneezing by an infected individual with Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2). 5,19 Symptoms of COVID-19 usually appear after an incubation period of about 5 days. The most common symptoms are fever, cough, fatigue, headache, and dyspnea. 5,19,20 In the most severe cases, patients may develop pneumonia, acute respiratory failure, distress syndrome, and acute heart problems. 5,19,20 Anosmia or partial loss of the sense of smell, usually accompanied by changes in taste, is a frequent symptom that helps in the diagnosis of COVID-19. 21-28 It is often a transitory

Otolaryngologic Manifestation and Long-Term Outcome in Mild COVID-19: Experience from a Tertiary Care Centre in India

“…Unlike non-COVID-19 post-viral anosmia, local factors causing ''conductive'' anosmia is not the underlying cause as seen by the limited number of patients manifesting other nasal symptoms as seen in this study (n = 3) and the study by Mercante et al (14%) [8]. MRI focussing on the olfactory groove have identified hyperintensity on T-1 weighted sequences due to underlying microbleeding and hemosiderin deposition [19]. This finding further provides credence to the ''Neuro-COVID'' hypothesis by Fotuhi et al [20].…”

Olfactory taste disorder as a presenting symptom of COVID-19: a large single-center Singapore study

“…Both ACE2 and TMPRSS2 genes are found in the supporting cells of the human neuroepithelium, making them viable targets for SARS-CoV-2 infection. Damage to the olfactory bulb with the development of microbleeding and oedema, as seen on magnetic resonance imaging, have been reported in COVID-19 patients with OTD [ 19 , 20 ]. In contrast, human influenza A virus binds to α2,6-linked sialic acid receptors, which are widely expressed in the respiratory tract [ 21 ].…”

COVID-19-Related Anosmia: The Olfactory Pathway Hypothesis and Early Intervention

“…On the day of discharge, after 23 days of hospitalization with partial recovery of the sense of smell, brain magnetic resonance imaging (MRI) showed smaller right olfactory blub and linear hyperintensities inside bilateral olfactory nerves, suggestive of bilateral olfactory neuropathy (44). A recent case series highlighted the abnormal intensity of the OBs in five COVID-19 adult patients, three of whom had anosmia, maybe due to abnormal enhancement or microbleeding because they only underwent the sequence after injection of gadolinium in fat-suppressed T1WI (45).…”