Chiari Malformations-Arnold–Chiari malformation, or often simply Chiari malformation, is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsilsthrough the foramen magnum (the opening at the base of the skull), sometimes causing non-communicating  hydrocephalus as a result of obstruction ofcerebrospinal fluid (CSF) outflow. The cerebrospinal fluid outflow is caused by phase difference in outflow and influx of blood in the vasculature of the brain. It can cause headaches, fatigue, muscle weakness in the head and face, difficulty swallowing, dizziness, nausea, impaired coordination, and, in severe cases, paralysis
Postural orthostatic tachycardia syndrome (POTS, also postural tachycardia syndrome) is a condition of dysautonomia, to be more specific orthostatic intolerance, in which a change from the supine position to an upright position causes an abnormally large increase in heart rate, called tachycardia. Several studies show a decrease in cerebral blood flow with systolic and diastolic cerebral blood flow (CBF) velocity decreased 44% and 60%, respectively. Patients with POTS have problems maintaining homeostasis when changing position, i.e. moving from one chair to another or reaching above their heads. Many patients also experience symptoms when stationary or even while lying down.
Symptoms present in various degrees of severity depending on the patient. POTS can be severely debilitating. Some patients are unable to attend school or work, and especially severe cases can completely incapacitate the patient.