Olfactory Bulb Volume, Olfactory Sulcus Depth in Parkinson's Disease, Atypical Parkinsonism.

Background: About 70-90% of Parkinson's disease (PD) patients have olfactory deficits which is considered as pre-motor symptom of PD. Lewy bodies have been demonstrated in the olfactory bulb (OB) in PD. Objective: To assess the OB volume (OBV), olfactory sulcus depth (OSD) in PD and compare with progressive supranuclear palsy (PSP), multiple system atrophy (MSA) and vascular parkinsonism (VP) patients and determine the cut-off volume of OB that will aid in the diagnosis of PD. Methods: This was a cross-sectional, hospital based, single-center study. Forty PD, 20 PSP, 10 MSA, 10 VP patients and 30 controls were recruited. OBV and OSD was assessed using 3-T magnetic resonance imaging (MRI) brain. Olfaction was tested using Indian Smell Identification test (INSIT). Results: The mean total OBV in PD was 113.3 ± 79.2 mm3 and 187.4 ± 65.0 mm3 in controls (P = 0.003) which was significantly lower in PD. The mean total OSD in PD was 19.4 ± 8.1 and 21.1 ± 2.2 mm in controls (P = 0.41) with no difference. The mean total OBV was significantly lower in PD as compared to that of PSP, MSA and VP patients. There was no difference in the OSD among the groups. The total OBV in PD had no association with age at onset, duration of disease, dopaminergic drugs dosage, motor and non-motor symptoms severity but had positive correlation with cognitive scores. Conclusion: OBV is reduced in PD patients as compared to PSP, MSA, VP patients and controls. OBV estimation by MRI adds to the armamentarium in the diagnosis of PD.