Feasibility and reliability of intraorally evoked "nociceptive-specific" blink reflexes

Abstract

Objectives: The "nociceptive-specific" blink reflex (nBR) evoked by extraoral stimulation has been used to assess trigeminal nociceptive processing in patients with trigeminal nerve damage regardless of the site of damage. This study aimed to test the feasibility of nBR elicited by intraoral stimulation, compare intraoral and extraoral nBR and assess the intrarater and interrater reliability of the intraoral nBR for the maxillary (V2) and mandibular (V3) branches of the trigeminal nerve.

Materials and methods: In 17 healthy participants, nBR was elicited by stimulation of two extraoral and two intraoral sites by two operators and repeated intraorally by one operator. Main outcome variables were intraoral stimulus-evoked pain scores and nBR R2 responses at different stimulus intensities. Intraclass correlation coefficients (ICC) were used to assess reliability.

Results: Dependent on the stimulus intensity, intraoral stimulation evoked R2 responses in up to 12/17 (70.6%) participants for V2 and up to 8/17 (47.1%) participants for V3. Pain scores (p < 0.003) and R2 responses (p < 0.004) increased with increasing intensities for V2, but not V3. The R2 responses were significantly smaller with intraoral stimulation compared to extraoral stimulation (p < 0.014). Overall, ICCs were fair to excellent for V2 but poor for V3.

Conclusion: Intraorally evoked nBR was feasible in a subset of healthy participants and was less responsive than nBR with extraoral stimulation. The V2 nBR showed better reliability than V3.

Clinical relevance: The nBR can be used to assess nerve damage to the maxillary intraoral regions, though other measures may need to be considered for the mandibular intraoral regions.

Keywords: Intraoral; Nociceptive blink reflex; Reliability; Trigeminal nerve.