Normative data for the lateralization task in the assessment of intranasal trigeminal function

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.

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 ± 4.1) 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.

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.

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.