Abstract
BACKGROUND: The intranasal trigeminal system contributes to the sense of smell. Its integrity in olfactory dysfunction (OD) may be crucial for future treatments. This study assessed trigeminal sensitivity in healthy individuals and patients with OD of different etiologies using electrical stimulation of the nasal mucosa. METHODS: Eighty-two participants were included in this multicentric study: healthy individuals (n = 28) and patients with OD (n = 54), comprising post-viral OD (PVOD, n = 29), post-traumatic OD (PTOD, n = 15), and chronic rhinosinusitis with nasal polyps (SND, n = 10). Olfactory function was assessed with the Sniffin' Sticks test battery; trigeminal sensitivity was measured via electrical thresholds at the anterior nasal septum. RESULTS: Age significantly affected electrical thresholds (ET), with older individuals showing higher thresholds (p = 0.012). In healthy participants, ET correlated positively with age (p = 0.02). PTOD patients exhibited higher ET compared to healthy individuals (p = 0.033), while PVOD and SND patients showed no significant differences. Anosmic patients had higher ET than hyposmic (p = 0.001) and normosmic individuals (p < 0.001); hyposmic and normosmic individuals did not differ significantly. Among age, etiology, and olfactory function, olfactory function was the most significant factor influencing ET (p = 0.013). All participants rated the stimulation as moderately intense and mildly painful, with ratings increasing with higher currents. CONCLUSIONS: Intranasal trigeminal function was largely preserved in OD patients, especially in hyposmic individuals. PTOD patients demonstrated the lowest trigeminal sensitivity.