Temperature thresholds in the oropharynx of patients with obstructive sleep apnea syndrome

The temperature thresholds for warmth and cold were determined on the oropharyngeal mucosa of 15 patients with obstructive sleep apnea syndrome (OSAS) and 15 age-matched nonsnoring control subjects. We found that six of the patients with OSAS were not able to detect either the upper (50 degrees C) or lower (25 degrees C) temperature limits of the test when recording from the tonsillar pillar, whereas all control subjects detected the temperature change within the measuring range. The OSAS patients showed a statistically significant higher threshold for warmth on the anterior tonsillar pillar, 46.8 degrees C (95% confidence interval 45.2-48.4) versus 42.5 degrees C (41.3-43.8) for the control subjects (p = 0.0006). The same was found on the tip of the tongue-40.1 degrees C (38.7-41.6) for OSAS patients and 38.2 degrees C (37.1-39.4) for the control subjects (p = 0.036). Determination of temperature thresholds on the skin is an established method of detecting a neuropathy. We speculate that patients with OSAS suffer from a neuropathy in the pharynx caused by prolonged and progressive trauma to the pharyngeal structures from vibration induced by snoring and/or stretching of the structures during apneas. A neuropathy may interfere with the normal stabilizing function of the pharyngeal muscles and with the local reflex mechanism preventing the upper airway from collapsing during inspiration. It is thus possible that snoring itself, by inducing a neuropathy in the pharynx, may contribute to the sequence of events that transform a snorer into a patient suffering from OSAS.