The purpose of this research study is to better understand what causes dysautonomia and how this affects blood pressure and pulse. Dysautonomia is a condition of the autonomic nervous system. It is associated with fluctuations in blood pressure and pulse and may cause symptoms of nausea and belly pain, fatigue, excessive thirst, lightheadedness, dizziness, feelings of anxiety or panic, and fainting. A common example of dysautonomia is postural orthostatic tachycardia syndrome or POTS. Sometimes symptoms worsen when people move from lying down to standing, called orthostatic intolerance. We would like to learn more about the link between orthostatic intolerance and nausea. While medications currently used to treat orthostatic intolerance and nausea have proven to be effective in some patients, this may not be the best treatment for everyone as long term use could pose certain risks including high blood pressure. In order to provide a more focused and safer treatment for patients suffering from nausea and orthostatic intolerance, we have looked at how the blood pressure, pulse, and certain blood tests change during a tilt table test. This test helps to create the same circumstances that patients with orthostatic intolerance experience when they stand. To better understand if some of these problems are associated with the brain, we will study MRI in patients with dysautonomia compared to children without dysautonomia. This information may allow us to use alternative and safer treatments in the future.

Inclusion Criteria:

• subjects who have completed tilt autonomic testing
• subjects from 9 - 18 years of age

Exclusion Criteria:

• subjects who have a metabolic, mechanical, or mucosal inflammatory cause which has been defined to explain their gastrointestinal symptoms
• Patients with cardiac or cardiovascular disease, malignancy, psychiatric illness, neurodevelopmental delay, or other co-morbid conditions
• Patients with with pacemakers, implanted devices, or any other MRI contraindications will be excluded from this study.

A combination of male and female subjects who are healthy or ahve dysautonomia/