Early and preclinical diagnosis of Parkinson's disease using olfactory testing and Diffusion Tensor Imaging of olfactory bulb and substantia nigra.

Parkinson's disease (PD) is only accurately diagnosed when the death of most of the specific brain cells, characteristic of the disease, is well advanced. Better ways must be found to detect PD earlier than this. Long before PD movement problems occur, changes happen in sense of smell and sleep patterns. Such changes are not enough to reveal the onset of PD. A combination of smell and sleep behaviour testing with a sensitive MRI-based brain imaging technique (called "DTI") may allow us to detect PD years before movement symptoms appear. New treatments are becoming available that may stop PD at an early stage, before lasting damage is done. Our study has 2 phases. Phase I (supported by Parkinson Society of Canada) studied 14 newly-diagnosed PD patients and compared them to 14 healthy subjects. In agreement with other studies, PD patients had an impaired sense of smell. Our new finding was that DTI imaging showed changes in water diffusion in brain tracts related to the sense of smell; there were also changes in another brain region. We will study performance on psychological tests, smell tests, and DTI brain changes in another group of PD patients and a population of patients with impairment of their thinking processes (i.e. patients with early Alzheimer's disease). The purpose of phase II, the largest part of our proposed study, is to detect PD in people at risk for PD but who have no current diagnosis of PD. We will screen 1,200 normal healthy people (age-matched siblings of PD patients) using a smell identification test. The lowest and highest 10% of responders in smell testing results will be assessed for sleep disorders and undergo a brain scan. Those with sleep disorders and smell deficits will have a high risk for PD. We will determine whether the combination of tests for smell ability, sleep disorders and brain imaging will allow effective detection of early stage PD.