Olfactory Bulb Volume and Olfactory Sulcus Depth in Patients With OSA: An MRI Evaluation

Abstract

Objectives: We evaluated olfactory functions in patients with obstructive sleep apnea (OSA). Methods: The cranial magnetic resonance images of 58 adult patients (36 males and 22 females) aged 27 to 79 years were retrieved from the hospital picture archiving and communication system (PACS) system. There were 29 patients with OSA (17 males and 12 females), diagnosed according to the polysomnography results. A control group consisted of 29 healthy patients without OSA. Olfactory bulb (OB) volume and olfactory sulcus (OS) depth measurements were performed. Nasal septal deviation (SD) was also evaluated and recorded as no SD, deviation to the right, and deviation to the left in all groups. Results: Olfactory bulb volumes of the OSA group were significantly lower than those of the control group ( P < .05), whereas OS depth values were not different ( P > .05). There was a positive correlation between the right and left OB volumes and right and left OS depth values ( P < .05). In older patients with OSA and in female patients with OSA, OB volumes decreased bilaterally ( P < .05). Olfactory sulcus depth of the right side was lower in the female patients with OSA compared to the male patients with OSA ( P < .05). There were no significant correlations between apnea–hypopnea index and OB volumes and OS depth values in the OSA group ( P > .05) Conclusion: In patients with OSA, OB volumes decreased bilaterally. It may be related to intermittent nocturnal hypoxia/reoxygenation episodes, which may be a trigger for upper airway inflammation; and proinflammatory mediators maybe harmful on olfactory neuroepithelium and olfactory impairment may occur.

The Effects of the Levels of Hypoxia in the Olfactory Nervous System in Mouse Model

“…2,19 In these studies, prolonged exposure to hypoxia can induce reduction in the number of olfactory neurons, which could be related to the damage of olfactory bulb in patients with OSA due of CIH. 19 Furthermore, despite the evidence of anatomical alterations in the olfactory system and functional changes in other neural circuits, induced by CIH, the specific effects of CIH on olfactory function have been directly assessed in other studies.…”

“…[16][17][18] Olfactory bulb volumes in the OSA group were significantly lower than those in the control group in some studies. 2,19 In these studies, prolonged exposure to hypoxia can induce reduction in the number of olfactory neurons, which could be related to the damage of olfactory bulb in patients with OSA due of CIH. 19 Furthermore, despite the evidence of anatomical alterations in the olfactory system and functional CNPase mRNA levels in the brain tissue were evaluated using RT-PCR.…”

“…2,19 In these studies, prolonged exposure to hypoxia can induce reduction in the number of olfactory neurons, which could be related to the damage of olfactory bulb in patients with OSA due of CIH. 19 Furthermore, despite the evidence of anatomical alterations in the olfactory system and functional CNPase mRNA levels in the brain tissue were evaluated using RT-PCR. S100b and NGFRAP1 mRNA levels in the olfactory neuroepithelium were higher in the 5% hypoxia group than those in the control group (S100b: 5% vs control, P = .027; NGFRAP1: 5% vs control, P = 1.0).…”

The potential for clinical application of automatic quantification of olfactory bulb volume in MRI scans using convolutional neural networks

“…Altogether this indicates the potential for applying this automated method in clinical settings in which olfactory bulb volume is relevant, for example in patients with depression ( Rottstaedt et al, 2018a ; Rottstaedt, Weidner, Hummel, & Croy, 2018b ), schizophrenia ( Asal et al, 2018 , Nguyen et al, 2011 ) or neurodegenerative diseases ( Marin et al, 2018 , Thomann et al, 2009 ). However, olfactory bulb volume is not only relevant for diseases that are primarily related to the brain; there is also evidence that it can be of clinical relevance in other patients, such as patients with obstructive sleep apnea ( Doğan et al, 2020 ), patients with obesity ( Karaoglan and Colakoglu Er, 2020 , Poessel et al, 2020 ). In addition, current studies showed that olfactory loss due to a COVID-19 infection can lead to atrophy of the olfactory bulb volume ( Chiu et al, 2021 , Tsivgoulis et al, 2021 ).…”

Peripheral and central olfactory measurements in Chronic Obstructive Pulmonary Disease patients

“…To measure OS depth, we examined coronal T2weighted SPIR sequence sections, and drew a virtual line connecting the "inferior orbital gyrus and gyrus recti in the posterior plane of the orbit." Then, we drew a perpendicular line from this point to the deepest point of the OS and measured the length of this line; this value represents OS depth and was recorded in millimeters 4,5 .…”