[Feature of semicircular canal function in obstructive sleep apnea-hypopnea syndrome]

The aim of this study was to evaluate the effects of obstructive sleep apnea-hypopnea syndrome (OSAHS) on semicircular canal function.

By means of a series prospective study at Department of Otolaryngology Head and Neck Surgery of our hospital, the study was performed on 77 patients suffering from OSAHS in a period from 2012 to 2014, who underwent polysomnography (PSG) and caloric test. The maximal slow-phase velocity (SPV) and unilateral weakness (UW) were used to measure the vestibular function. Severity of OSAHS was evaluated by the lowest oxygen saturation (LSaO₂) and apnea hypopnea index (AHI). The SPV after cool was signed, warm test was performed for each ear, and the sum of left ear SPV were calculated, and then, the SPV of right ear was counted as the same way. Finally, the relationships between LSaO₂, AHI, age, BMI, and SPV of caloric test were analyzed.

Caloric vestibular tests in the 77 OSAHS patients demonstrated abnormal findings in 52 patients (67.5%) and normal vestibular functions in the remaining 25 patients (32.5%). Of the 52 patients with an abnormal test result, 16 (20.8%) patients had unilateral vestibular hyporeflexia and 36 (46.7%) patients revealed a bilateral vestibular hyporeflexia. There was no linear relationship between AHI, age, BMI with SPV of caloric test (P > 0.05). The SPV had significant difference between Lower LSaO₂group (LSaO₂< 50%) and higher LSaO₂group (LSaO₂≥ 80%) (P < 0.05). LSaO₂was lower in patients undertaken bilateral vestibular hyporeflexia.

OSAHS patients with long-term intermittent hypoxia can disturb the vestibular organs and reduce semicircular canal function. The heavier hypoxemia will lead to the lower reflex of semicircular canal, with the heavier degree of hypoxemia, and the bilateral horizontal semicircular canal involvement may also be higher at the same time. Due to the effect of vestibule centre compensatory, OSAHS patients lack of dizziness and symptoms from balance disturbances such as typically acute vestibular damage.