Quantitative sensory testing, obstructive sleep apnea and peripheral nervous lesions

In diagnosis of peripheral neuropathies, quantitative sensory testing (QST) is used to assess thermal and vibration sensitivity. QST is a psychophysical method susceptible to the influence of several factors. It is important to standardize the test. Vibrations may cause peripheral nerve lesions. Snoring induces oropharyngeal vibrations which could cause nervous lesions and consequent obstructive sleep apnea (OSA).

Objectives: to study the effect of anatomical site, applied pressure and local skin temperature on QST. To develop methodology for QST and EMG in oropharynx. To evaluate the presence of oropharyngeal nerve lesions in patients with OSA and snoring.

Methods: Thermal and vibration thresholds were tested in 47 normal subjects at different sites in hand and foot. The effect of different local pressures on vibration thresholds and of different skin temperatures on thermal thresholds was studied. In 14 habitual snorers and 31 OSA-patients vibration detection thresholds (VDT) and cold detection thresholds (CDT) were tested intra-orally. Comparison was made to 23 non-snoring individuals. Concentric needle EMG was performed in m. palatoglossus in OSA patients, habitual snorers and normal subjects.

Results: In general, the hand was more sensitive than the foot to QST. Thenar was most sensitive to warmth. There were no other significant differences between any of the sites within the hand or foot for thermal or vibration stimuli. Warm and cool thresholds were independent of local skin temperature. Different applied pressures did not change VDT. In OSA-patients, both VDT and CDT were elevated at the tonsillar pillars compared to non-snorers. VDT were not significantly different between snorers and normals, but this was true for CDT (p=0.001). In 10/11OSA patients, palatoglossus EMG showed signs of motor neuropathy. 11/22 habitual snorers showed moderate pathology.

Conclusion: In the hand, the preferred site for thermal testing is the thenar eminence and for VDT the pulp of the index finger. Warming or cooling of the skin is unnecessary. Low pressure differences did not influence the results of VDT. Signs of palatal motor and sensory nervous lesions were present in most OSAS-patients and some snorers, supporting the hypothesis of a progressive nervous lesion. CDT and EMG could be used to evaluate structural damage, which might be important to identify snorers at risk and in choice of therapy.

List of scientific papers

I. Hagander LG, Midani HA, Kuskowski MA, Parry GJ (2000). Quantitative sensory testing: effect of site and skin temperature on thermal thresholds. Clin Neurophysiol. 111(1): 17-22.
https://doi.org/10.1016/S1388-2457(99)00192-3

II. Hagander LG, Midani HA, Kuskowski MA, Parry GJ (2000). Quantitative sensory testing: effect of site and pressure on vibration thresholds. Clin Neurophysiol. 111(6): 1066-9.
https://doi.org/10.1016/S1388-2457(00)00278-9

III. Hagander L, Harlid R, Svanborg E (2006). Oropharyngeal vibration and thermal sensivity in patients with obstructive sleep apnea and snoring. [Submitted]

IV. Svanborg E, Hagander L, Haraldsson PO, Harder L, Hultcrantz E (2006). Electromyographic findings in upper airway muscles of patients with obstructive sleep apnea and snoring. [Submitted]