Association of olfactory bulb volume and olfactory sulcus depth with olfactory function in patients with Parkinson disease

Abstract

Background and purpose: Olfactory dysfunction is commonly associated with IPD. We here report the association of OB volume and OS depth with olfactory function in patients with PD.

Materials and methods: Morphometric analyses by using MR imaging and the Japanese T&T olfactometer threshold test were used to evaluate olfactory structure and function in 29 patients with PD and 29 age- and sex-matched healthy controls.

Results: The olfactory recognition thresholds were significantly higher in patients with PD than in healthy controls (3.82 ± 1.25 versus 0.45 ± 0.65, P<.001). Olfactory atrophy with reductions in the volume of the OB (37.30 ± 10.23 mm(3) versus 44.87 ± 11.84 mm(3), P<.05) and in the depth of OS (8.90 ± 1.42 mm versus 9.67 ± 1.24 mm, P<.05) was observed in patients with PD but not in controls. Positive correlations between olfactory performance and OB volumes were observed in both patients with PD (r=-0.45, P<.0001) and in controls (r=-0.42, P<.0001). In contrast, there was no significant correlation between the depth of OS and olfactory function in either cohort.

Conclusions: The results provide evidence that early olfactory dysfunction in patients with PD may be a primary consequence of damage to the OB. Neuroimaging of olfactory structures together with the assessment of olfactory function may be used to identify patients with PD.

Fig 1.

Visualization of the OB and the OS on representative MR images. Coronal (A) and sagittal (B) views of the brain show the OB (white arrows). Coronal T2-weighted (C) and T1-weighted (D) images show the OS (white arrowhead).

Fig 2.

T&T olfactometer threshold tests in patients with PD and in healthy controls. The means of recognition thresholds are significantly higher in patients with PD than in control subjects. Data are expressed as means ± SEM.

Fig 3.

OB volume (A) and OS depth (B) in patients with PD and in healthy controls. The mean OB volumes and the mean OS depths are statistically smaller in patients with PD than in control subjects. Data are expressed as means ± SEM.

Fig 4.

Correlation of the volume of OB with olfactory performance in patients with PD (A) and in healthy controls (B). In patients with PD and in controls, the OB volumes correlate positively with odor recognition threshold scores.