Multisensory modulation of experimentally evoked perceptual distortion of the face

Abstract

Background

Chronic orofacial pain patients often perceive the painful face area as 'swollen' without clinical signs, i.e., a perceptual distortion (PD). Local anesthetic (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 of could be modulated by adding mechanical stimulation (MS) to the affected area

Methods

MS was given with a brush and a 128 mN von Frey filament. First, sixty healthy participants were randomly divided into three groups: 1) LA control, 2) LA with MS, 3) 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 = 0.089), filament (p = 0.203). However, when the filament stimulation was combined with additional visual information of a distorted face there was observable decrease in PD (p = 0.002)

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.

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