Quantitative Sensory Testing in Patients with Bell's Palsy

Aim of the Study: Patients with facial palsy often report sensory symptoms over the paretic part of the face. To test for the presence of sensory disturbances we applied a battery of sensory tests according to the Quantitative Sensory Testing (QST) protocol of the German Research Network on Neuropathic Pain (GRNP) over ipsi- and contralateral parts of the face. Methods Sixteen patients with idiopathic facial palsy and 32 controls were studied. All patients were investigated within 3 days after onset of symptoms. Seven tests were performed determining 13 variables over ipsi- and contralateral cheeks and forehead including thermal (cold and warm perception threshold, thermal sensory limen, paradoxical heat sensations, cold pain and heat pain thresholds) and mechanical stimuli (von Frey filaments, pinprick stimuli, vibration threshold using a tuning fork, and pressure pain thresholds using a handheld algometer). Results: Heat pain threshold was lowered by 1.3 °C over the ipsilateral face (p=0.036; ANOVA; LSD post hoc-test) without a significant cheek-forehead difference. All other pain thresholds were not reduced (p>0.16). Additionally, thermal and mechanical perception thresholds tended to be increased over the affected side of the face. However, this effect was only significant for cold perception threshold (p=0.02; ANOVA; LSD post hoc-test), again with no cheek-forehead difference. These findings were not related to the presence of dysaesthesia (6 out of 16 patients). Conclusion: Our finding of heat pain hyperalgesia in patients with facial palsy is consistent with peripheral rather than central sensitization of nociceptive neurons, probably due to a trigeminal affection. This result also contributes to the old concept of polyneuritis cranialis rather than mononeuritis facialis in patients with idiopathic facial palsy (Adour et al. Arch Otolaryngol 1976; 102: 262–264). Supported by GRNP (BMBF grant 01EM0107) and MAIFOR (University of Mainz).