Central mechanisms of pain amplification of chronic orofacial myofascial pain: analysis of experimental modulation of the nociceptive blink reflex.

• Grant number: 24/12764-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2024
• End date: August 31, 2026
• Field of knowledge: Biological Sciences - Physiology
• Principal Investigator: Yuri Martins Costa
• Grantee: Isadora Alves Lorenzo
• Host Institution: Faculdade de Odontologia de Piracicaba (FOP). Universidade Estadual de Campinas (UNICAMP). Piracicaba , SP, Brazil
• Associated research grant: 19/15826-8 - Central mechanisms of pain amplification in patients with chronic myofascial orofacial pain: exploring new potentialities of somatosensory and neurophysiological assessment, AP.JP

Abstract

This study aims to characterize patients with chronic orofacial myofascial pain according to the modulatory response of local anesthesia and capsaicin in the neurophysiological profile, assessed through the nociceptive blink reflex. For this, 35 patients with primary chronic orofacial myofascial pain will be evaluated. Therefore, this experimental, double-blind, randomized and placebo-controlled study will be conducted through consecutive experimental sessions separated by 24 hours. Sessions will involve sensory modulation using local anesthesia and topical capsaicin. In local anesthesia modulation sessions, patients will receive 30 minutes of application of 4% lidocaine cream and a placebo cream to the region of the skin covering the most painful masseter and the forearm. These sessions will take place under two different conditions: 2 ml of 0.5% lidocaine and 2 ml of isotonic saline solution (0.9%). In topical capsaicin modulation sessions, participants will receive 45 minutes of application of 1% capsaicin to the same sites mentioned above. The nociceptive blink reflex will be assessed in the nerve exit region of the infraorbital nerve and conditioned pain modulation will be assessed in the baseline and final sessions. The analyzes will primarily involve the identification of subgroups of patients with chronic orofacial myofascial pain according to the modulatory response of local anesthesia and capsaicin on the neurophysiological profile through the absolute differences in Z scores between the lidocaine, placebo and capsaicin sessions and the baseline sessions.