Olfactory Radioanatomical Findings in Patients With Cardiac Arrhythmias, COVID-19, and Healthy Controls

Background Clinical hyposmia and anosmia are commonly seen, most frequently with either post-inflammatory, age-related, or idiopathic causes being most frequent. Actual anatomical abnormalities of the olfactory groove or olfactory bulb are far less common. A recent case report showing a possible link between congenital olfactory bulb agenesis and Wolff-Parkinson-White syndrome suggested that there may be a relationship between cardiac arrhythmia and olfactory bulb development. While Kallmann syndrome (KS) is the classic syndrome involving olfactory bulb agenesis and hypogonadotropic hypogonadism, this case report and a prior report noting isolated hypogonadotropic hypogonadism and the Wolff-Parkinson-White syndrome suggest there may be more rare associations between cardiac arrhythmia and olfactory groove abnormalities. Methods A retrospective study was conducted to attempt to elucidate whether there may be a link between cardiac arrhythmias and olfactory anatomical abnormalities. The olfactory bulb volume (OBV) and olfactory sulcus depth (OSD) of 44 patients with cardiac arrhythmias were compared to 43 healthy control patients. Additionally, 11 patients with acute COVID-19 were also compared in those groups. Patients were seen between September and December 2020. Available MRI images were utilized. Results The average right and left olfactory bulb volume was 29.42±18.17 mm³ and 25.67±15.29 mm³ for patients with cardiac arrhythmia, 40.79±30.65 mm³ and 38.95±21.87mm³ for healthy controls, and 21.30±15.23 mm³ and 17.75±9.63 mm³ for COVID-19 patients. The average right and left olfactory sulcus depth was 7.68±1.31 mm and 7.47±1.56 mm for patients with cardiac arrhythmia, 10.67±1.53 mm and 10.62±1.67 mm for controls, and 7.91±0.99 mm and 8.02±0.88 mm for COVID-19 patients. The right and left olfactory bulb volume difference versus controls was significant for cardiac arrhythmia patients (p=0.028 and p=0.0038) and for COVID-19 patients (p=0.047 and p=0.0029), and the right and left olfactory sulcus depth difference versus controls was significant for cardiac arrhythmia patients (p<0.0001 and p<0.0001) and for COVID-19 patients (p<0.0001 and p<0.0001). Both COVID-19 and cardiac arrhythmia patients were, on average, significantly older than controls. On multivariate analysis, cardiac arrhythmia or COVID-19 diagnosis did not significantly correlate with smaller olfactory bulb volume, but older age, cardiac arrhythmia diagnosis, and COVID-19 diagnosis did significantly correlate with smaller olfactory sulcus depth. On multivariate analysis, older age was significantly correlated with cardiac arrhythmia diagnosis and COVID-19 diagnosis. Conclusions Olfactory bulb volume and olfactory sulcus depth in both cardiac arrhythmia and COVID-19 patients appeared significantly smaller than in controls. Cardiac arrhythmia and COVID-19 patients were significantly older than controls. Age, as well as genetic predisposition, may contribute to a difference in the radiographic olfactory anatomical findings in patients with cardiac arrhythmias and COVID-19.