Inclusion Criteria:

• Males or females ≥ 40 years of age;
• Presenting (within the last 3 months) for an initial evaluation to a movement disorders specialist with signs or symptoms suggestive of a movement disorder;
• The subject's signs or symptoms were previously evaluated by a physician who was not a movement disorders specialist during the previous six months;
• Absence of an established clinical movement disorder diagnosis;
• Symptoms mild in intensity, this includes Hoehn & Yahr ≤ 2 (Exceptions are allowed for subjects who meet criteria for Hoehn & Yahr stage 3 due to early onset of postural instability and/or gait impairment out of proportion to his/her other Parkinson signs and symptoms);
• Montreal Cognitive Assessment (MoCA) score ≥ 22;
• Can tolerate imaging visit procedures; and
• Provide written informed consent prior to study entry.

Exclusion Criteria:

• Have been referred to the movement disorders clinic primarily for the purpose of disease management (no diagnostic uncertainty exists on the part of the non-specialist or referring physician);
• Have a previous movement disorder diagnosis given by a movement disorders specialist prior to the time of enrollment;
• Have received a total of more than 90 days treatment with dopaminergic medications, including direct dopamine agonists or precursors (levodopa) or have received a total of more than 180 days treatment with MAO-B inhibitors, amantadine, anticholinergics or primidone or beta-blockers prescribed for treatment of tremor or signs of parkinsonism;
• Have had a sustained and clinically meaningful response to anti-parkinsonian medications;
• Are currently taking or have taken MAO-B inhibitors in the past 4 weeks;
• Have a known CNS structural lesion such as stroke or tumor that likely accounts for their symptoms;
• Have clinically meaningful cognitive impairment or dementia (mild cognitive problems as might be expected in the earliest stages of PD are not exclusionary);
• Have current clinically significant cardiovascular disease or clinically important abnormalities on screening ECG (including but not limited to QTc > 450 msec);
• Are currently taking medications that are known to cause QT-prolongation;
• Are currently taking medications with narrow therapeutic windows (e.g. warfarin or other anticoagulant therapies);
• Are currently taking tetrabenazine (TBZ), amphetamine type drugs;
• Have a current clinically significant endocrine or metabolic disease, pulmonary, renal or hepatic impairment, or cancer (excluding localized basal cell carcinoma and in situ prostate cancer) that would interfere with completion of the study;
• Have a recent history (within the past year) of alcohol or substance abuse or dependence;
• Are females of childbearing potential who are not surgically sterile, not refraining from sexual activity or not using reliable contraception. Females must not be pregnant (negative serum beta-hCG at the time of screening and negative urine beta-hCG on the day of imaging), must not be breastfeeding at screening, must avoid becoming pregnant and use adequate contraceptive methods for 14 days prior to and 24 hours after administration of 18F-AV-133 for injection;
• Have had prior intracranial surgery; and
• Are receiving any investigational medications, or have participated in a trial with investigational medications within the last 30 days.