Late olfactory bulb involvement in COVID-19

Area of Science:

• Neurology
• Radiology
• Otorhinolaryngology

Background:

• Olfactory dysfunction, including hypo-anosmia, is a common symptom of SARS-CoV-2 infection.
• Late-term morphometric changes in the olfactory pathway following COVID-19 are not fully understood.

Purpose of the Study:

• To evaluate late olfactory bulb (OB) imaging changes in neurologically asymptomatic COVID-19 patients.
• To correlate these OB changes with olfactory function after infection.

Main Methods:

• Eighty-three COVID-19 patients and 25 healthy controls underwent 3T-MRI and olfactory function tests (questionnaire, Sniffin' Sticks).
• Maximal OB area was measured blindly on high-resolution coronal T2w images.
• Patients were subgrouped based on olfactory function recovery.

Main Results:

• Former COVID-19 patients exhibited a significantly decreased mean maximal OB area compared to controls (6.52 ± 1.11 mm² vs. 7.26 ± 1.17 mm²).
• This reduction was observed regardless of persistent hypo-anosmia or recovered normosmia.
• No significant differences in OB size were found among COVID-19 patient subgroups.

Conclusions:

• SARS-CoV-2 infection is associated with mid/late-term morphological changes in the olfactory bulb.
• These OB changes occur irrespective of the presence or persistence of olfactory dysfunction.
• Further research is needed on long-term olfactory aging and potential links to neurodegenerative disorders.