Bell's Palsy-Retroauricular Pain Threshold

Abstract

Background and objectives: Non-motor symptoms in the form of increased sensitivity are often associated with the onset of idiopathic Bell's palsy (IBP). The aims were to determine whether the pain threshold in the retroauricular regions (RAR) in IBP patients and the time of its occurrence is related to IBP severity. Materials and Methods: The study was conducted among 220 respondents (142 IBP patients, 78 healthy subjects (HS)). The degree of IBP was graded using the House-Brackmann and Sunnybrook Grading Scales (II-mild dysfunction, VI-total paralysis), whereas the pain thresholds were measured using the digital pressure algometer. Results: We found no difference in the degree of the pain threshold between the right and left RAR in the HS group. IBP patients belonging to groups II, III, IV, and V had lower pain thresholds in both RARs than HS and IBP patients belonging to group VI. There was no difference in the degree of pain threshold in RAR between the affected and unaffected side in IBP patients. The incidence of retroauricular pain that precedes paralysis and ceases after its occurrence in groups II and III of IBP patients is noticeably lower and the incidence of retroauricular pain that occurred only after the onset of paralysis is more frequent. Also, we found that the incidence of retroauricular pain that precedes paralysis and ceases after its occurrence in groups V and VI of IBP patients was more frequent. Conclusions: The degree of pain threshold lowering in RAR (bilaterally) is inversely related to the severity of IBP. We suggest that the occurrence of retroauricular pain before the onset of facial weakness is associated with higher severity of IBP while the occurrence after the onset is associated with lower severity of IBP.

Keywords: digital pressure algometer; ephaptic coupling; idiopathic Bell’s palsy; mirror-image pain threshold; pain threshold; retroauricular pain.

Figure 1

Pain threshold values in the RAR of healthy controls and patients with Bell’s palsy on the affected side. Pain threshold levels of each group are presented as average (lack dots) ± standard deviation (whiskers). One-way ANOVA revealed a statistically significant difference among the groups and Tukey’s HSD post hoc p values are presented.

Figure 2

Pain threshold values among patients with Bell’s palsy regarding the affected side. Pain threshold levels of the affected side (black dots) and the healthy side (black triangles) are presented as averages ± standard deviation (whiskers). Pain threshold was assessed by two-way ANOVA (factors: group—II, III, IV, V, VI; side—affected/healthy side). There was no interaction effect (p = 0.968), but a significant effect of group (p < 0.001) and side (p < 0.001).