IADR Abstract Archives
Somatosensory Function, Pain, and Unpleasantness in Trigeminal Nerve Damage Models
Objectives: To test the hypothesis that topical application of local anesthetics and capsaicin to the trigeminal region differentially influences the somatosensory function of the face in healthy participants.
Methods: This study was randomized, crossover, placebo-controlled, and double-blinded. 20 healthy participants (mean age 25.5±4.7 years) underwent three separate sessions. Each session consisted of infraorbital region assessment of pain, unpleasantness, and somatosensory function using quantitative sensory testing (QST) and electrically evoked nociceptive-specific trigeminal blink reflex (nBR) before and after a topical application of either: 0.1% capsaicin, local anesthetics (EMLA), or vaseline (placebo). All parameters were analyzed using ANOVA and Spearman’s correlation tests.
Results: Pain and unpleasantness scores were significantly higher for capsaicin (pain: 45.7±27.6, unpleasantness: 44.2±27.2, p<0.001) but not for EMLA (pain: 4.0±3.2, unpleasantness: 4.0±5.7, p=0.165) when compared with vaseline (pain/unpleasantness: 0.0). For EMLA, sensory loss was seen in cold and warmth detection (CDT, WDT), thermal sensory limen (TSL), cold pain threshold (CPT), mechanical detection threshold (MDT), mechanical pain threshold (MPT), mechanical pain sensitivity (MPS) and vibration detection threshold (VDT) (p<0.028). Capsaicin application caused sensory loss in WDT, TSL and CPT (p<0.025). Electrically evoked sensory and pain thresholds (IP) were significantly increased after capsaicin and EMLA application (p<0.014). After capsaicin application, the electrical pain scores significantly decreased at stimulation with 150% and 200% of IP (p=0.023). The electrical pain scores decreased for all stimulation intensities after EMLA application (p<0.001). The nBR responses were significantly decreased at 150% and 200% of IP threshold after EMLA application (p<0.023) and at 200% and 300% after capsaicin application (p<0.021). Electrically evoked pain and mechanical pain sensitivity was significantly positively correlated at all electrical stimulus intensities (r>0.484, p<0.031).
Conclusions: Application of EMLA and capsaicin evoked differential somatosensory changes when assessed using QST and nBR and may act as surrogates of sensory disturbances seen in trigeminal nerve injury.
Methods: This study was randomized, crossover, placebo-controlled, and double-blinded. 20 healthy participants (mean age 25.5±4.7 years) underwent three separate sessions. Each session consisted of infraorbital region assessment of pain, unpleasantness, and somatosensory function using quantitative sensory testing (QST) and electrically evoked nociceptive-specific trigeminal blink reflex (nBR) before and after a topical application of either: 0.1% capsaicin, local anesthetics (EMLA), or vaseline (placebo). All parameters were analyzed using ANOVA and Spearman’s correlation tests.
Results: Pain and unpleasantness scores were significantly higher for capsaicin (pain: 45.7±27.6, unpleasantness: 44.2±27.2, p<0.001) but not for EMLA (pain: 4.0±3.2, unpleasantness: 4.0±5.7, p=0.165) when compared with vaseline (pain/unpleasantness: 0.0). For EMLA, sensory loss was seen in cold and warmth detection (CDT, WDT), thermal sensory limen (TSL), cold pain threshold (CPT), mechanical detection threshold (MDT), mechanical pain threshold (MPT), mechanical pain sensitivity (MPS) and vibration detection threshold (VDT) (p<0.028). Capsaicin application caused sensory loss in WDT, TSL and CPT (p<0.025). Electrically evoked sensory and pain thresholds (IP) were significantly increased after capsaicin and EMLA application (p<0.014). After capsaicin application, the electrical pain scores significantly decreased at stimulation with 150% and 200% of IP (p=0.023). The electrical pain scores decreased for all stimulation intensities after EMLA application (p<0.001). The nBR responses were significantly decreased at 150% and 200% of IP threshold after EMLA application (p<0.023) and at 200% and 300% after capsaicin application (p<0.021). Electrically evoked pain and mechanical pain sensitivity was significantly positively correlated at all electrical stimulus intensities (r>0.484, p<0.031).
Conclusions: Application of EMLA and capsaicin evoked differential somatosensory changes when assessed using QST and nBR and may act as surrogates of sensory disturbances seen in trigeminal nerve injury.