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

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.