Magnetic Resonance Spectroscopy in Autonomic Failure

This research study will be conducted in patients with primary autonomic failure, a disabling condition that is associated with low blood pressure upon standing. These patients are also not able to control for changes in their blood pressure due to a loss of cardiovascular reflexes that are mediated within the brain. The purpose of this study is to determine whether magnetic resonance spectroscopy (MRS), a non-invasive imaging technique, can measure levels of chemicals (neurotransmitters) in the dorsal medulla, a brain area important for control of cardiovascular function, in autonomic failure patients. Importantly, this study will determine whether there are differences in brain chemicals between patients with peripheral versus central origins of their autonomic failure. The hypothesis is that the neurotransmitter profile in the medulla will be intact in patients with peripheral autonomic failure compared to those with central impairment. Overall, this study will provide insight into understanding the mechanisms involved in autonomic failure and will determine whether a single session of MRS imaging can improve the ability to make an accurate diagnosis in these patients. This would lessen the need for more extensive and invasive clinical testing.