Olfactory dysfunction in behavioral variant frontotemporal dementia

Several neurodegenerative disorders show olfactory dysfunction. In patients with frontotemporal dementia (FTD), olfactory impairment is probably due to the involvement of the temporal and orbitofrontal lobes. We hypothesized that due to the disrupted areas in FTD, there would be an impairment in smell identification, differentiation and association. Moreover, we hypothesized that there would be a correlation between the severity of FTD and the severity of odor dysfunction.

In the current study, we compared odor identification, discrimination and association of nine patients with behavioral variant FTD with eleven healthy controls using the Brief Smell Identification Test and the Odor Perception and Semantics Battery.

The results showed significant differences in the odor association test, but not in the identification or discrimination test. There was no correlation between disease severity and the performance in the odor tests.

We showed impairment of odor association that is most likely due to disruption of specific associative areas involved in olfactory processing. Specifically, we propose that the impairment may well be due to disrupted areas in the temporal lobe and amygdala.