AIM: To provide normative data for the lateralization task in the assessment of intranasal trigeminal function, as well as to investigate potential effects of age, sex and olfactory function.

METHODS: The lateralization task using eucalyptus as target stimulus was performed to assess intranasal trigeminal function. Data were collected from: 360 healthy adult participants (mean age 37.5±17.4) for the 40-trial version; 284 participants (mean age 32.6±14.1) for the 20-trial version; and 418 participants (mean age 42.6±15.6) for the 10-trial version. The "Sniffin' Sticks" test was used to measure olfactory function.

RESULTS: The mean scores were 35.46±4.50 for the 40-trial version, 15.64±3.65 for the 20-trial version, and 8.14±2.16 for the 10-trial version. In the reference group aged 18-25 years, the 10th percentiles were 33 for the 40-trial version, 11 for the 20-trial version, and 6 for the 10-trial version. Significant effects of age and odor discrimination score were observed on lateralization performance.

CONCLUSIONS: We provide reference scores for the lateralization task, in large sample of healthy participants. Among the three examined tasks (40, 20 and 10), the 40-trial task yielded the most reliable information. For the 40-trial version, scores equal or higher to 33 points indicate a normal lateralization ability, whereas scores between 27 and 32 may warrant further assessment. Scores below 27 possibly point towards a decreased trigeminal function. The lateralization task serves as surrogate marker of intranasal trigeminal functions and further studies with pathological cases are needed to explore its clinical usefulness.