Evaluation of the olfactory bulb volume and morphology in patients with coronavirus disease 2019: can differences create predisposition to anosmia?

SUMMARY OBJECTIVE: This study aimed to investigate whether the volume and morphology of the olfactory bulb are effective in the occurrence of anosmia in patients after COVID-19 infection. METHODS: The olfactory bulbus volume was calculated by examining the brain magnetic resonance imaging of cases with positive (+) COVID-19 polymerase chain reaction test with and without anosmia. Evaluated magnetic resonance imaging images were the scans of patients before they were infected with COVID-19. The olfactory bulbus and olfactory nerve morphology of these patients were examined. The brain magnetic resonance imaging of 59 patients with anosmia and 64 controls without anosmia was evaluated. The olfactory bulb volumes of both groups were calculated. The olfactory bulb morphology and olfactory nerve types were examined and compared between the two groups. RESULTS: The left and right olfactory bulb volumes were calculated for the anosmia group and control group as 47.8±15/49.3±14.3 and 50.5±9.9/50.9±9.6, respectively. There was no statistically significant difference between the two groups. When the olfactory bulb morphology was compared between the two groups, it was observed that types D and R were dominant in the anosmia group (p<0.05). Concerning olfactory nerve morphology, type N was significantly more common in the control group (p<0.05). CONCLUSIONS: According to our results, the olfactory bulb volume does not affect the development of anosmia after COVID-19. However, it is striking that the bulb morphology significantly differs between the patients with and without anosmia. It is clear that the evaluation of COVID-19-associated smell disorders requires studies with a larger number of patients and a clinicoradiological approach.

Study on the clinical characteristics of isolated congenital anosmia / 中华耳鼻咽喉头颈外科杂志

Objective: To retrospectively analysely the electrophysiological and imaging features of isolated congenital anosmia (ICA) and to assess the clinical phenotypic characteristics and classification of ICA. Methods: Clinical data of 30 ICA patients in Beijing Anzhen Hospital from 2012 to 2019 was retrospectively reviewed, including 13 males and 17 females, aged (35±19) years. The control group consisted of 30 healthy people from medical examination center, including 13 males and 17 females, aged (39±14) years. The clinical characteristics of ICA were analyzed using Sniffin' Sticks test, olfactory event-related potentials (oERPs), trigeminal event-related potentials (tERP) and olfactory pathway MRI. SPSS 17.0 software was used to compare the difference of olfactory function between the two groups. The correlation between olfactory bulb, olfactory sulcus structure and age was observed, and the clinical phenotype characteristics of ICA patients were analyzed. Results: The subjective olfactory function was completely lost in ICA patients. oERP was absent in all of the ICA patients, but showed normal N1 and P2 waves in controls. tERP could be evoked in 63.3% (19/30) of ICA patients, and signals in these patients showed higher amplitude in the N1 ((-10.33±6.93) μV vs (-5.11±2.71) μV, t=-10.113, P<0.01) and P2 ((+17.25±8.51) μV vs (+7.31±3.46) μV, t=5.443, P<0.01) waves than that of the controls. Olfactory bulbs were aplastic in 80.0% (24/30) of patients and hypoplastic in 20.0% (6/30) of patients. Fifty-six point seven percent (17/30) of patients had bilateral olfactory sulcus deletion while 43.3% (13/30) had dysplasia, and all of the patients exhibited a depth of olfactory sulcus less than 8 mm. Both the structure of olfactory bulbs and olfactory sulcus were not associated with age for ICA patients (r value was -0.174 and 0.325, respectively, all P>0.05). Conclusions: ICA patients show neurophysiologic deficits and some anatomic differences compared with healthy controls. The absence of oERP combining with a depth of olfactory sulcus less than 8 mm is the important indicator for clinical diagnosis of ICA. The structure of olfactory bulb may be a critical factor for clinical classification of ICA.