Biomarkers in Neural Disorders

This study seeks to establish the sensitivity and specificity of what appears to be a unique brainstem biomarker of Parkinson's Disease (PD) - an electrically induced olygosynaptic nasotrigeminal reflex response - in differentiating early stage PD from normal controls and from patients with various other neurodegenerative diseases. This study will additionally compare the biomarker to olfactory testing.

Parkinson's disease (PD), a devastating age-related disease that is clinically defined by its effects on the motor system, afflicts more than six million people worldwide, imposing enormous burdens on patients, relatives, caretakers, and society in general. Diagnostic errors are common, particularly as symptoms first arise. The most common misdiagnoses are Alzheimer's disease (AD), essential tremor, and vascular pseudo-Parkinson's Disease. An accurate diagnosis is typically made at a later stage of the disease when marked and irreversible damage has occurred within the motor control system of the brain. Sensitive and specific biomarkers of the early stages of PD are urgently needed. Identification of such markers is critical for the development and assessment of medications and other interventions designed to eliminate or reduce the gradual and irreversible decline of neurons involved in the disorder. This study seeks to establish the sensitivity and specificity of what appears to be a unique brainstem biomarker of PD - an electrically induced trigeminal nerve blink reflex response - in differentiation of early stage PD from normal controls and such neurodegenerative diseases as early stage AD, progressive supranuclear palsy (PSP), and diffuse Lewy Body disease (DLBD). This study will additionally compare the biomarker to olfactory test results.

Eligibility Criteria:
Inclusion Criteria:

* The Parkinson's disease (PD) patients will be Hoehn and Yahr stage 2 or less with a history of motor symptoms less than two years.
* The Alzheimer's disease (AD) patients will meet the 2011 National Institute on Aging-Alzheimer's Association and the 1984 National Institute for Neurological and Communicative Disorders and Stroke-Alzheimer's disease and Related Disorders Association criteria for probable AD.
* The progressive supranuclear palsy (PSP) patients will have met the NINDS-SPSP criteria for probable PSP, which requires vertical supranuclear gaze palsy, prominent postural instability, and falls in the first year of onset, as well as a number of other clinical features.
* The DLBD patients will meet the Consensus Criteria for the clinical diagnosis of DLBD.
* The healthy controls will be matched to the PD patients on such variables as sex, age, education level, and ethnicity.
* The essential tremor (ET), multiple system atrophy (MSA), myasthenia gravis (MG), multiple system atrophy (MSA), Parkinson's disease dementia (D-PD), and Spinal Cord Injury (SCI) patients will meet the generally-accepted diagnostic criteria for these disorders.

Exclusion Criteria:

* Drug abuse.
* Any other known and potentially confounding condition that could reasonably be expected to interfere with the study assessments.
* Under age 18.
* Over age 80.
* Smoker.
* Pregnant or nursing.
* Healthy control with a first degree relative who has a neurodegenerative disease.