It has been shown that the olfactory bulb is one of the two main regions where PD seems to begin .
The many studies were undertaken because it was discovered that smell tests can differentiate PD from progressive supranuclear palsy , essential tremor , and parkinsonism induced by MPTP .
PD has been shown that the olfactory bulb is one of the two main regions where PD seems to begin .
The many studies were undertaken because it was discovered that smell tests can differentiate PD from progressive supranuclear palsy , essential tremor , and parkinsonism induced by MPTP .