Peripheral and central smell regions in COVID-19 positive patients: an MRI evaluation

Coronaviruses may lead to invasion of the central nervous system.

To investigate the effects of COVID-19 infection on smell using cranial magnetic resonance imaging (MRI).

Cranial MRI scans of 23 patients with COVID-19 (patient group [PG]) and 23 healthy controls (HCs) were evaluated. Peripheric (olfactory bulb [OB] volume and olfactory sulcus [OS] depth) and central (insular gyrus and corpus amygdala areas) smell regions were measured.

Smell loss was present in nine patients (39.1%) in the PG. The means of the disease duration and antiviral treatment were 3.00 ± 2.35 and 5.65 ± 1.72 days, respectively. OB volumes of the PG were significantly lower than those of the HCs bilaterally. However, no significant differences were observed between the OS depth, insular gyrus, and corpus amygdala areas of both groups. The left corpus amygdala areas were both increased with the increased disease (P = 0.035, r = 0.442) and treatment durations (P = 0.037, r = 0.438). In the PG, longer treatment duration, increase in C-reactive protein (CRP), lymphocyte count decrease, and positive thoracic computed tomography (CT) involvement were related to OS depth decrease. Right corpus amygdala areas increased in patients with COVID-19 with increased D-dimer values, and thoracic CT involvement was detected.

COVID-19 disease affects the peripheric smell region of OBs and does not affect the central smell regions of the insular gyrus and corpus amygdala areas. The importance of our study is to detect MRI findings in patients with COVID-19 leading to odor disorders. These findings may help in diagnosing the disease at an early stage.