Aim
Olfactory dysfunction (OD) is a common presenting symptom of COVID-19 infection. Radiological imaging of olfactory structures in patients with COVID-19 and OD can potentially shed light on their pathogenesis and guide clinicians in prognosis and intervention.
Methods
PubMed, Embase, Cochrane, SCOPUS were searched from inception to August 1, 2021. Three reviewers selected observational studies, case series, and case reports reporting radiological changes in olfactory structures, detected on magnetic resonance imaging. , computed tomography, or other imaging modalities, in patients ≥18 years of age with COVID-19 infection and OD, following preferred reporting items for systematic reviews and meta-analyses guidelines and a protocol registered in PROSPERO (CRD42021275211).
We described the proportion of radiological outcomes and used random-effects meta-analysis to pool the prevalence of olfactory cleft opacification, olfactory bulb signal abnormalities, and olfactory mucosal abnormalities in patients with and without COVID-19-associated OD.
Results
We included 7 case-control studies (N = 353), 11 case series (N = 154), and 12 case reports (N = 12).
The pooled prevalence of olfactory cleft opacification in patients with COVID-19 infection and OD (63%, 95% CI = 0.38–0.82) was significantly higher than that in controls (4%, 95% CI = 0.38–0.82). 95% = 0.01–0.13).
In contrast, similar proportions of cases and controls demonstrated olfactory bulb signal abnormalities (88% and 94%) and olfactory mucosal abnormalities (2% and 0%).
Descriptive analysis found that 55.6% and 43.5% of patients with COVID-19 infection and OD had morphological abnormalities of the olfactory bulb and olfactory nerve, respectively, while 60.0% had abnormal volumes. of the olfactory bulb.
Conclusion Our findings implicate a driving mechanism of olfactory dysfunction located in the olfactory cleft, in approximately half of affected COVID-19 patients. |
Comments
How does COVID-19 affect people’s ability to smell?
A decreased or altered sense of smell, called olfactory dysfunction, is a common symptom experienced by people with COVID-19. As described in an article published in The Laryngoscope, researchers recently searched the medical literature for studies reporting changes in olfactory structures detected through imaging tests of COVID-19 patients.
The prevalence of an olfactory cleft abnormality was almost 16 times higher in patients with COVID-19 and olfactory dysfunction (63%) compared to controls (4%). The olfactory clefts provide a crucial channel for molecules in the air to reach the olfactory sensory neurons that connect to the brain to allow a person to perceive odors.
“Before this study, most scientists thought that the loss of smell in COVID-19 was mainly due to inflammation and damage to the olfactory nerves. “Now, we have gathered evidence from medical imaging that loss of smell from COVID-19 is also due to edema and blockage of the odor-conducting passages in the nose,” said lead author Neville Wei Yang Teo, MRCS, MMed, Singapore General Hospital.
"We think this is good news for patients who want to recover their sense of smell, as these blocks are expected to resolve over time, while nerve damage in comparison is probably more difficult to recover," the author added. principal, Claire Jing-Wen. Tan, of the National University of Singapore. “However, these findings may not fully explain those who suffer from long-term olfactory dysfunction, and additional studies evaluating patients in this group may provide more information.”
