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 = 4) or motor deficits (n = 1). This olfactory bulb injury may be the mechanism by which the Severe Acute Respiratory Syndrome coronavirus 2 causes olfactory dysfunction.

FIG 1.

MR imaging shows probably microbleeding (methemoglobin) in the left olfactory bulb of a patient (case 1) with COVID-19 and anosmia. The left olfactory bulb (long arrows) has partial hyperintensity on precontrast fat-suppressed T1WI (A) and also on postcontrast fat-suppressed T1WI (B) and STIR (C).

FIG 2.

The coronal postcontrast fat-suppressed T1WI shows hyperintensity suggestive of enhancement or methemoglobin in the olfactory bulbs of 4 patients with COVID-19 (A–D; cases 2–5) compared with a healthy patient with normal olfactory bulbs (E and F). The coronal postcontrast fat-suppressed T1WI in 3 patients with COVID-19 (A–C; cases 2–4) shows that both olfactory bulbs (long arrows) are small oval images that are hyperintense with contrast, having signal intensity higher than the intensity of the cortex. D, A patient (case 5) with COVID-19 shows hyperintensity only on the left bulb (long arrow), the right olfactory bulb being normal (short arrow). In a healthy 60-year-old man, the coronal T2WI (E) and the postcontrast fat-suppressed T1WI (F) demonstrate normal olfactory bulbs (long arrows), which are isointense to the cortex and normally hypointense on postgadolinium sequence (F).