Olfactory Dysfunction, Olfactory Bulb Volume and Alzheimer's Disease: Is There a Correlation? A Pilot Study1

BACKGROUND Olfactory dysfunction is present since the earliest stage of Alzheimer's disease (AD). In AD patients, the olfactory impairment has been correlated with atrophy of some structures of the olfactory system, but the role of the olfactory bulb remains unclear. OBJECTIVE The aim of our work is to test if patients suffering from AD exhibit a statistically significant reduction of the average volume of the olfactory bulb (OBV) compared to healthy subjects. METHODS 78 subjects were enrolled in the study and divided into three groups: 28 healthy elderly (22 females, 6 males, mean age 69.4 ± 9.2), 25 patients with mild cognitive impairment (MCI) amnestic type (14 females, 11 males, mean age 74.5 ± 7.5), and 25 mild AD patients (14 females, 11 males, mean age 73.7 ± 6.8). Every subject underwent an MRI study of the olfactory bulb and an olfactory assessment with the Sniffin' Stick Extended Test. RESULTS The statistical analysis showed no correlation between the OBV and MCI or AD. Moreover, olfactory function and OBV were not correlated in any of the three groups. CONCLUSION The reduction of OBV does not seem to represent an index of neuronal damage in the earliest stages of AD.