Striatal and Extra-striatal Mechanisms of Falling in Parkinson's Disease
Striatal and Extra-striatal Mechanisms of Falling in Parkinson's Disease
This research study will evaluate functions of memory, thinking, eye movements and walking
 and how these relate to the measurement of certain chemicals (acetylcholine and dopamine) in
 the brain using an imaging procedure called positron emission tomography (PET). You may know
 that the brain chemical dopamine, a "neurotransmitter" substance (a chemical messenger that
 nerve cells need to communicate with each other), is important for the brain to control
 movements and that the brain chemical acetylcholine may have functions related to mental
 concentration and attention. At the present time, the investigators have no clear information
 how these two chemicals in the brain of patients with Parkinson's disease are related to the
 risk of falling.
Although most research in PD has a focus on presynaptic dopaminergic denervation, new lessons
 may be learned by exploring to what extent alterations in non-motor and non-dopaminergic
 systems may play a role in the balance impairment in this disorder. This project is designed
 to evaluate striatal pre-synaptic dopaminergic, cortical, thalamic, and brainstem
 cholinergic, cognitive, and oculomotor mechanisms underlying the risk of falling and
 imbalance in PD. The proposed study will exploit advances in our center in the development of
 dynamic biomathematical modeling of electronic platform data, application of specialized
 cognitive and oculomotor assessments, and positron emission tomography (PET). This novel
 multi-system approach holds promise for understanding mechanisms of falling in PD beyond
 pre-synaptic dopaminergic nigrostriatal denervation.
Inclusion Criteria:

 -  Subjects considered for inclusion will be female or male subjects either currently
 enrolled or eligible for care at the VA aged 50-85 years, or community volunteers.

 -  The racial, gender and ethnic characteristics of the proposed subjects population
 reflect the demographics of the patient population of the VA. However, extra efforts
 will be made to recruit women and minorities (see table 5).

 -  Children will be excluded from the study.

 -  No exclusion criteria shall be based on race, ethnicity, gender, or asymptomatic HIV
 status.

 Exclusion Criteria:

 -  Inability to stand or walk independently (i.e., patients in Hoehn and Yahr stage IV
 and V).

 -  Vertiginous disorder.

 -  Orthostatic hypotension or unstable cardiovascular disease at risk of syncope (drop in
 systolic blood pressure of > 20 mm Hg upon standing).

 -  History of stroke with focal cortical lesions.

 -  Cerebellar, myelopathic or significant radiculopathy syndrome.

 -  Diminished light perception in both eyes (< 20/40 corrected OU).

 -  Intracranial surgery.

 -  Subjects who have participated in other research protocols such that their cumulative
 radiation absorbed dose to whole body, gonads, bone marrow or lens of the eye would
 exceed 5 Rem, or dose to other body organs is more than 15 Rem in preceding 12 months.

 -  Pregnancy (beta-HCG test within 48 hours of PET study) or breastfeeding.

 -  Contra-indications to MRI.