Title : Olfactory bulb changes on brain MRI in adult patients with anosmia due to COVID-19: a systematic review
Background: COVID-19 or coronavirus is a global pandemic, which is correlated with anosmia. This study aimed to summarize the Brain MRI finding in patients with anosmia due to COVID-19.
Methods: This systematic review was performed following the Preferred Reporting Items for Systematic Reviews and meta-analyses (PRISMA) reporting guidelines. A systematic literature search was done on 28th of January 2021 using PubMed, ScienceDirect, OVID/Medline and Embase. Studies reporting data sufficient to evaluate the olfactory bulb using MRI in patients with COVID-19 were included in the qualitative synthesis. Quality was assessed using the Newcastle-Ottawa scale (for observational cohort and case-control), AXIS tool (for cross-sectional), and quality assessment tool (for case series and case report). Information about demographics, MRI timing and findings, and duration of anosmia were extracted from the involved studies with subsequent qualitative evidence synthesis.
Results: The search identified 139 results. Nine studies were eligible and were included in this systematic review. Brain MRIs of patients in the included studies showed olfactory bulb hyperintensity or atrophy in many patients, and olfactory bulb enlargement in another group. One study also showed irregular contour or deformed J shape of olfactory bulb, and a shallow olfactory sulcus. The time of undergoing MRI scanning for these patients varies; some studies had MRI in the first weeks from onset of anosmia and others in months later, or after partial recovery form anosmia.
Conclusion: Most common changes on brain MRI are hyperintensity or atrophy. Also, few cases showed enlargement, and others showed changes in bulb shape.