Objective:
In dysautonomias, altered functions of one or more components of the autonomic nervous system adversely affect health. Primary dysautonomias have been classified clinically into chronic autonomic failure (CAF) syndromes that include pure autonomic failure (PAF), multiple system atrophy (MSA), and Parkinson disease (PD) with autonomic failure (manifested especially by neurogenic orthostatic hypotension (OH)). Clinical assessment alone is often inadequate for correct diagnosis and does not provide insights into mechanisms or identify new therapeutic targets. This protocol calls for continuous development and assessment of physiological, neuropharmacologic, neurochemical, neuroimaging, and other clinical laboratory approaches, to identify lesion types and sites in CAF and improve diagnosis, increase mechanistic understanding, and incite novel therapeutics. PAF, MSA, and PD exemplify alpha synucleinopathies, in which deposits of the protein alpha-synuclein occur in Lewy bodies in catecholamine-producing neurons (PD, PAF) or in the cytoplasm of glial cells (MSA). Only the Lewy body forms of synucleinopathy are consistently associated with loss of catecholaminergic neurons. Under this protocol we have obtained evidence that patients with Lewy body diseases have decreased ability to take up intra-neuronal catecholamines from the cytoplasm into storage vesicles. Cytoplasmic catecholamines are cytotoxic, such as by enzyme-catalyzed conversion to highly reactive catecholaldehydes. By studying CAF patients we hope to make discoveries that will yield a unifying, integrative concept for the pathogenesis and different clinical manifestations of Lewy body diseases. Autonomic function testing under this protocol is also required for screening purposes for entry into other protocols of the Clinical Neurocardiology Section. Moreover, comprehensive autonomic function testing is requested in patients of the NIH Undiagnosed Diseases Program. Finally, in a long-term project as a member of the Autonomic Rare Diseases Clinical Research Consortium we are applying this testing to study the natural history of neurogenic OH.
Study Population:
The study population consists of patients with idiopathic, or primary, CAF, with emphasis on PAF, MSA, and PD. Comparison groups include healthy volunteers (HVs), patients with PD who do not have OH, and patients with iatrogenic CAF such as from bilateral thoracic sympathectomies.
Design: Subjects undergo multiple physiological, neuropharmacologic, neurochemical, and neuroimaging, and other tests, to see if the results by different modalities agree and point to specific sites and types of lesions.
Outcome Measures:
Physiological outcome measures include hemodynamic responses to the Valsalva maneuver, orthostasis, and altered temperature at skin of the back. Neuropharmacologic measures include cardiovascular responses to test drugs that probe specific components of the autonomic nervous system. Neurochemical measures include plasma, cerebrospinal fluid, microdialysate, urine, and skin biopsy tissue levels of catecholamines and related compounds. Neuroimaging measures include positron emission tomographic scanning after injection of 18F-dopamine, 18F-DOPA, 13N-ammonia, or 11C-methylreboxetine.