Nasal chemosensory tests: biomarker between dementia with Lewy bodies and Parkinson disease dementia.

BACKGROUND

Dementia with Lewy bodies (DLB) and Parkinson disease dementia (PDD) are progressive and disabling neurodegenerative disorders, which are often misdiagnosed due to theirs overlapping clinical and paraclinical features. Nevertheless, their adequate management requires an accurate differential diagnosis. The main aim of this study was to investigate the usefulness of olfactory and trigeminal nasal testing for the differential diagnosis between DLB and PDD.

METHODS

Odor thresholds to three odorants differentially activating the olfactory and trigeminal systems were assessed in patients with DLB, PDD and healthy controls (n = 20 per group).

RESULTS

Odor thresholds were significantly different between the three groups of subjects. More precisely, we found that DLB patients had significantly lower detection threshold performances compared to PDD patients. Moreover, using a standard canonical discriminant analysis, we confirmed a plain differentiation between the three groups.

CONCLUSIONS

The current study highlights that DLB patients have very poor olfactory and trigeminal detection threshold performances, which are significantly lower, compared to PDD patients. These results suggest that olfactory testing, using odorants that stimulate both the olfactory and trigeminal systems, could constitute an interesting biomarker and contribute to the differential diagnosis of PDD and DLB patients. Further researches, notably on olfacto-trigeminal interactions, are warranted in these populations to support our findings.