Experimental orofacial pain and sensory deprivation lead to perceptual distortion of the face in healthy volunteers

Abstract

Patients suffering from persistent orofacial pain may sporadically report that the painful area feels "swollen" or "differently," a phenomenon that may be conceptualized as a perceptual distortion because there are no clinical signs of swelling present. Our aim was to investigate whether standardized experimental pain and sensory deprivation of specific orofacial test sites would lead to changes in the size perception of these face areas. Twenty-four healthy participants received either 0.2 mL hypertonic saline (HS) or local anesthetics (LA) into six regions (buccal, mental, lingual, masseter muscle, infraorbital and auriculotemporal nerve regions). Participants estimated the perceived size changes in percentage (0 % = no change, -100 % = half the size or +100 % = double the size), and somatosensory function was checked with tactile stimuli. The pain intensity was rated on a 0-10 Verbal Numerical Rating Scale (VNRS), and sets of psychological questionnaires were completed. HS and LA were associated with significant self-reported perceptual distortions as indicated by consistent increases in perceived size of the adjacent face areas (P ≤ 0.050). Perceptual distortion was most pronounced in the buccal region, and the smallest increase was observed in the auriculotemporal region. HS was associated with moderate levels of pain VNRS = 7.3 ± 0.6. Weak correlations were found between HS-evoked perceptual distortion and level of dissociation in two regions (P < 0.050). Experimental pain and transient sensory deprivation evoked perceptual distortions in all face regions and overall demonstrated the importance of afferent inputs for the perception of the face. We propose that perceptual distortion may be an important phenomenon to consider in persistent orofacial pain conditions.

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

“…Moreover, the patients' reports of perceptual distortions might be biased, as patients may be more inclined to answer 'yes' when asked directly about a specific phenomenon. However, the patients specifically described the perceptual distortions as perceived swelling and not reduction of the painful area, which is in agreement with reports of perceptual distortions in healthy volunteers (5,15), and we therefore find it unlikely that the patient's reports of perceptual distortions indicate a strong response bias. Secondly, the patients were consecutively recruited based on the main inclusion criteria of chronic oro-facial pain.…”

“…However, the present findings mirror results from a study in patients with CRPS, showing that body image disruptions were positively related to pain intensity (23). It has been previously demonstrated that perceptual distortions of the face in healthy volunteers can be induced by nociceptive stimulation (5,15). Therefore, it is possible that nociceptive stimulation, at least partially, may lead to the perceptual distortions observed in oro-facial pain patients.…”

“…To estimate the magnitude of perceptual distortion, the patients were asked to rate the perceived magnitude of the perceptual distortion on a Magnitude Estimation Scale (MES) ranging from −100% to +100% (−100% = half‐size, 0 = no change, +100% = double size). This method is in accordance with our previously used rating scale and employed to cover both decreases and increases in perceived magnitude of the involved face area .…”

Multisensory modulation of experimentally evoked perceptual distortion of the face

“…Perceptual distortion (PD) is a form of disorder in the way one experiences one's own body in terms of size and shape. Descriptions of such distortion are commonly encountered in the dental clinic due to peripheral sensory deprivation of the region with local anaesthetics (LA) . Furthermore, distortion of corporal awareness has been documented for patients suffering from various psychological and neurological conditions, accounting non‐painful such as phantom sensations and anorexia nervosa, and painful conditions such as oro‐facial pain, complex regional pain syndrome and phantom limb pain .…”

“…The study is based on a previously published model of evoked PD of the face and explores the impact of different sensory components on the shifted body representation of a distorted perception in healthy volunteers. The overall aim of this study was to enhance the understanding on how individuals process sensory components in a stimulus‐response settings targeting PD.…”