Quantitative Sensory Testing Assessing Extraterritorial Neurosensory Abnormalities in Atypical Odontalgia

Objectives: QST is a neurosensory testing method that delivers stimuli to body surfaces and assesses subject responses via quantitative scales.   Previous QST work in patients with Atypical Odontalgia (AO), a chronic unilateral orofacial pain condition, found neurosensory changes not only in the region of chronic facial pain but also on the contralateral, asymptomatic side.  This pilot study aims to assess to what extent neurosensory changes spread to all three divisions of the trigeminal nerve in those with and without AO.

Methods: QST protocol of 13 tests was used to measure three divisions of the trigeminal nerve bilaterally in AO cases and controls with no pain. Testing employed controlled thermal, tactile and painful stimuli applied to the gingiva (intraoral), face (extraoral) and hand (control site).

Results: The QST battery was conducted on 6 extraoral and 4 intraoral sites in all three trigeminal divisions in 10 controls (6 Female, aged 42-62), (4 Male, aged 21-73) and the first 3 AO cases (3 Female, aged 39 - 59). QST battery showed unique patterns of altered neurosensation even though each subject’s clinical phenotype was similar: 40 to 50 year old female with chronic continuous pain in their mandibular molar region for 2+ year including: massive A-beta sensory loss after #19 endosseous implant placement that spread to the maxillary region (mechanical detection threshold (MDT): 16 vs. 0.4 mN), sensory gain of only C fibers in all four quadrants (cold pain threshold: 19 vs. 12°C), and sensory loss of A-beta, A-delta and C fibers that spread to the maxillary quadrant(MDT: 301 vs. 21 mN). 

Conclusion: Painful regions show neurosensory abnormalities, and early findings are consistent with the hypothesis that altered neurosensation spreads to non-painful nerve divisions. The technique is promising as a diagnostic test and in defining the neural mechanisms of trigeminal pain disorders.