How should sensory function in the oropharynx be tested? Cold thermal testing; a comparison of the methods of levels and limits

Abstract Objective Several studies indicate an upper airway peripheral neuropathy in obstructive sleep apnea syndrome (OSAS). The sensation of cold, as measured by cold detection thresholds (CDT), in the oropharynx has been shown to be compromised in patients with sleep apnea and, to a lesser extent, habitual snoring. To reveal whether this neuropathy is part of the pathogenetic process of OSAS, longitudinal studies of snorers are needed. The objective of the present study was to establish the test–retest repeatability for the two most commonly used thermal testing methods: the reaction time exclusive method of levels (MLE) and the method of limits (MLI). Methods Forty non-snoring subjects were tested at the soft palate and the lip at two separate occasions (mean interval 45 days) using a Medoc TSA – 2001 equipment with an intra-oral thermode. Results With MLE mean CDT’s were lower for both the lip and soft palate than with MLI. However, MLI showed a better test–retest repeatability ( r = 2.2 vs. 2.6) for the soft palate. Conclusions MLI should be used in longitudinal studies. The performance of this method is also faster. Significance We have established a quick, safe and reliable method suitable for longitudinal studies of peripheral neuropathy in sleep apnea pathogenesis.