Development of a new psychophysical method to assess intranasal trigeminal chemosensory function.

BACKGROUND: The aim of this study was to develop a new psychophysical test to assess intranasal trigeminal chemosensory function. METHODOLOGY: The test is similar to the Sniffin’ Sticks test, but using pens impregnated with substances preferentially activating trigeminal afferents. Our test comprises detection threshold, discrimination, identification and lateralization tasks. In a first study, we evaluated healthy controls. In a second study, we evaluated the potential usefulness of this test in patients with rhinological conditions. RESULTS: Study 1: 86 controls were included. Threshold, identification and lateralization performance decreased with age. Test-retest reliability was similar to that of olfactory tests. Study 2: results of the controls group were compared to those of 59 patients (14 allergic rhinitis, 11 chronic rhinosinusitis with nasal polyps (CRSwNP), 9 without nasal polyps (CRSsNP), and 25 with an olfactory disorder (OD)). Controls had 1) lower detection thresholds compared to CRSwNP, CRSsNP and OD, 2) better discrimination and identification scores compared to OD, and 3) better lateralization scores compared to CRSwNP and CRSsNP. CONCLUSIONS: Our test allows to identify age-related changes in trigeminal chemosensory function. Trigeminal function seems to be differently affected in different pathologies. Further studies are necessary to validate our results and evaluate the impact of olfactory co-activation on the observed results.