Reports of perceptual distortion of the face are common in patients with different types of chronic oro-facial pain

Facial recognition, laterality judgement, alexithymia and resulting central nervous system adaptations in chronic primary headache and facial pain-A systematic review and meta-analysis

INTRODUCTION

Patients with chronic headaches and chronic oro-facial pain commonly present psychosocial issues that can affect social interactions. A possible reason could be that patients with these disorders might present impairments in facial recognition, laterality judgement and also alexithymia. However, a systematic review summarizing the effects of facial emotion recognition, laterality judgement and alexithymia in individuals with headaches and oro-facial pain is still not available.

AIM

The main objective of this systematic review (SR) and meta-analysis (MA) was to compile and synthesize the evidence on the occurrence of alexithymia, deficits in laterality or left-right (LR) recognition and/or facial emotion recognition (FER) in patients with chronic headache and facial pain.

METHODS

Electronic searches were conducted in five databases (up to September 2023) and a manual search to identify relevant studies. The outcomes of interest were alexithymia scores, speed and accuracy in LR and/or FER, or any other quantitative data assessing body image distortions. The screening process, data extraction, risk of bias and data analysis were performed by two independent assessors following standards for systematic reviews.

RESULTS

From 1395 manuscripts found, only 34 studies met the criteria. The overall quality/certainty of the evidence was very low. Although the results should be interpreted carefully, individuals with chronic headaches showed significantly higher levels of alexithymia when compared to healthy individuals. No conclusive results were found for the other variables of interest.

CONCLUSION

Although the overall evidence from this review is very low, people with chronic primary headaches and oro-facial pain could be regularly screened for alexithymia to guarantee appropriate management.

Development of the 12-Item Facial Complaints Evaluation Scale (FaCES-12)

OBJECTIVES

Chronic rhinosinusitis and related rhinologic disorders are common in routine otolaryngologic practice. Common presenting symptoms include nasal obstruction, facial pain, facial pressure, headache, and a subjective feeling of the face feeling "swollen," a perceptual distortion. No validated scale exists to assess facial pain in addition to perceptual distortion or headache. The objective was to develop a novel scale for assessment of facial symptoms experienced by patients presenting for rhinologic evaluation.

METHODS

This was a prospective validation cross-sectional study. A patient questionnaire, the 12-item Facial Complaints Evaluation Scale (FaCES-12), was created to evaluate facial symptoms based on clinical experience and the literature, including severity and timing of facial pain, facial pressure, facial perceptual swelling, and headache. Each item was assessed utilizing an 11-point Likert scale ranging from 0 to 10 in severity. Data was collected prospectively from 210 patients in 1 private and 2 academic otolaryngologic practices from August to December 2019 along with the PROMIS Pain Intensity Scale 3a and 22-Item Sino-nasal Outcome Test. Construct validity was determined using Pearson correlation and exploratory factor analysis. Internal consistency and test-retest reliability were assessed by calculating Cronbach's alpha and assessing test-retest scores.

RESULTS

A new 12-item scale named FaCES-12 was developed. FaCES-12 demonstrated high reliability with a Cronbach's alpha of .94 and high test-retest reliability (r = .90). The scale revealed very strong correlation with the PROMIS Pain Intensity Scale 3a (r = .81) and moderate correlation with the Sino-nasal Outcome Test (r = .48). Exploratory factor analysis demonstrated the scale contained interrelated variables that measured unique components of facial sensations.

CONCLUSION

The FaCES-12 is a valid and reliable instrument for use in the evaluation of facial symptoms. Further research into the application of this scale is warranted.

The sensorimotor theory of pathological pain revisited

Harris (1999) proposed that pain can arise in the absence of tissue damage because changes in the cortical representation of the painful body part lead to incongruences between motor intention and sensory feedback. This idea, subsequently termed the sensorimotor theory of pain, has formed the basis for novel treatments for pathological pain. Here we review the evidence that people with pathological pain have changes to processes contributing to sensorimotor function: motor function, sensory feedback, cognitive representations of the body and its surrounding space, multisensory processing, and sensorimotor integration. Changes to sensorimotor processing are most evident in the form of motor deficits, sensory changes, and body representations distortions, and for Complex Regional Pain Syndrome (CRPS), fibromyalgia, and low back pain. Many sensorimotor changes are related to cortical processing, pain, and other clinical characteristics. However, there is very limited evidence that changes in sensorimotor processing actually lead to pain. We therefore propose that the theory is more appropriate for understanding why pain persists rather than how it arises.

Facilitatory Effect of Intermittent Repetitive Transcranial Magnetic Stimulation on Perceptual Distortion of the Face

Orofacial pain patients often report that the painful facial area is "swollen" without clinical signs - known as perceptual distortion (PD). The neuromodulatory effect of facilitatory repetitive transcranial magnetic stimulation (rTMS) on PD in healthy individuals was investigated, to provide further support that the primary somatosensory cortex (SI) is involved in facial PD. Participants were allocated to active (n = 26) or sham (n = 26) rTMS group in this case-control study. PD was induced experimentally by injecting local anesthesia (LA) in the right infraorbital region. PD was measured at baseline, 6 min after LA, immediately, 20 and 40 min after rTMS. Intermittent theta-burst stimulation (iTBS) as active rTMS and sham rTMS was applied to the face representation area of SI at 10 min after LA. The magnitude of PD was compared between the groups. The magnitude of PD significantly increased immediately after iTBS compared with sham rTMS (P = .009). The PD was significantly higher immediately after iTBS compared to 6 min after LA (P = .004) in the active rTMS group, but not in the sham rTMS group (P = .054). iTBS applied to a somatotopic-relevant cortical region appears to facilitate facial PD further supporting the involvement of SI in the processing of one´s own face and PD. PERSPECTIVE: This study provides information on neural substrate responsible for processing of perceptual distortion of the face which is speculated to contribute to the chronification of orofacial pain. The findings of this study may aid in mechanism-based management of the condition in orofacial pain disorders and possibly other chronic pain states.

Effect of repetitive transcranial magnetic stimulation on altered perception of One's own face

BACKGROUND

Chronic orofacial pain (COP) patients often perceive the painful face area as "swollen" without clinical signs; such self-reported illusions of the face are termed perceptual distortion (PD). The pathophysiological mechanisms underlying PD remain elusive.

OBJECTIVE

To test the neuromodulatory effect of repetitive transcranial magnetic stimulation (rTMS) on PD in healthy individuals, to gain insight into the cortical mechanisms underlying PD.

METHODS

PD was induced experimentally by injections of local anesthetic (LA) around the infraorbital nerve and measured as perceived size changes of the affected area. Participants were randomly allocated to inhibitory rTMS (n = 26) or sham rTMS (n = 26) group. The participants rated PD at baseline, 6 min after LA, immediately, 20 and 40 min after rTMS. The rTMS (inhibitory and sham) was applied to face (lip) representation area of primary somatosensory cortex (SI) as an intervention at 10 min after the LA, when the magnitude of PD is large. As inhibitory rTMS, continuous theta-burst stimulation paradigm (50 Hz) for 40s was employed to inhibit cortical activity.

RESULTS

We demonstrated a significant decrease in the magnitude of PD immediately and 20 min after the application of inhibitory rTMS compared with sham rTMS (P < 0.006). In two control experiments, we also showed that peripheral muscle stimulation and stimulation of a cortical region other than the lip representation area had no effect on the magnitude of the PD.

CONCLUSIONS

Inhibitory rTMS applied to a somatotopical-relevant cortical region modulates PD of the face in healthy individuals and could potentially have therapeutic implications for COP patients.

Multisensory modulation of experimentally evoked perceptual distortion of the face

BACKGROUND

Chronic oro-facial pain patients often perceive the painful face area as "swollen" without clinical signs, that is a perceptual distortion (PD). Local anaesthetic (LA) injections in healthy participants are also associated with PD.

OBJECTIVE

The aim was to explore whether PD evoked by LA into the infraorbital region could be modulated by adding mechanical stimulation (MS) to the affected area.

METHODS

Mechanical stimulation was given with a brush and a 128-mN von Frey filament. Firstly, sixty healthy participants were randomly divided into three groups: (i) LA control, (ii) LA with MS, (iii) isotonic solution (ISO) with MS as an additional control condition. To further examine the role of a multisensory modulation, an additional experiment was conducted. Twenty participants received LA with MS (filament) in addition to visual feedback of their distorted face. The results of the two experiments are presented together.

RESULTS

All three LA groups experienced PD; per contra, PD was not reported in the ISO group. MS alone did not change the magnitude of PD: brush (P = .089), filament (P = .203). However, when the filament stimulation was combined with additional visual information of a distorted face, there was observable decrease in PD (P = .002).

CONCLUSION

The findings indicate the importance of multisensory integration for PD and represent a significant step forward in the understanding of the factors that may influence this common condition. Future studies are encouraged to investigate further the cortical processing for possible implications for PD in pain management.

Neuropathic orofacial pain: Facts and fiction

Definition and taxonomy This review deals with neuropathic pain of traumatic origin affecting the trigeminal nerve, i.e. painful post-traumatic trigeminal neuropathy (PTTN). Symptomatology The clinical characteristics of PTTN vary considerably, partly due to the type and extent of injury. Symptoms involve combinations of spontaneous and evoked pain and of positive and negative somatosensory signs. These patients are at risk of going through unnecessary dental/surgical procedures in the attempt to eradicate the cause of the pain, due to the fact that most dentists only rarely encounter PTTN. Epidemiology Overall, approximately 3% of patients with trigeminal nerve injuries develop PTTN. Patients are most often female above the age of 45 years, and both physical and psychological comorbidities are common. Pathophysiology PTTN shares many pathophysiological mechanisms with other peripheral neuropathic pain conditions. Diagnostic considerations PTTN may be confused with one of the regional neuralgias or other orofacial pain conditions. For intraoral PTTN, early stages are often misdiagnosed as odontogenic pain. Pain management Management of PTTN generally follows recommendations for peripheral neuropathic pain. Expert opinion International consensus on classification and taxonomy is urgently needed in order to advance the field related to this condition.