I came across this interesting article in Sleep Medicine, where they showed that in patients with obstructive sleep apnea, a significant number were hemodynamically hyperviscosity positive (282/610 patients). Hyperviscous means that blood is thicker and more prone to clog arteries. Of these 282 patients, 239 had brainstem AEP abnormalities. AEPs are tests for ear neurologic reflexes where clicks are given in one ear and brain waves are measured in response. It tests for inner ear and brainstem function.
Ones that didn’t have hyperviscosity all had normal AEPs. Of these 239 patients, 57 had bilateral sensorineural hearing changes (no waves at all), and 182 patients had significant bilateral signal changes. After 6 months of CPAP, hyperviscosity was normalized in 159 patients. In 112 of these 159 patients a repeat AEP became normal. Of the 80 patients on CPAP that did not normalize, hemodilution therapy resulted in normalization in 61 patients. Hemodilution is when blood is made thinner by removing some blood and adding some saline.
This paper talks about bilateral conditions but also brings up the possibility of unilateral sudden sensorineural hearing loss being explained by this mechanism. It’s in line with my personal observation that every patient that I see with sudden sensorineural hearing loss has a history and exam consistent with an underlying sleep-breathing disorder. The handful that agreed to undergo sleep studies showed significant obstructive sleep apnea in all cases. I think the implications of this paper are enormous.