Hello @atlas. I was recently diagnosed with Autonomic Neuropathy (also called Autonomic Dysfunction). Like you, I have Orthostatic Hypotension too. Phoenix Neurological Associates is now Honor Healthcare and that's where I was referred to in 2015. (In 2015, I was diagnosed with severe Small Fiber Neuropathy).
There were several tests performed to confirm my Autonomic Neuropathy diagnosis which included: tilt table, sweat output, breathing, etc. Those tests were done at the Scottsdale Mayo Clinic. I also had a brain MRI, hearing tests, EMG with NCS, and saw an Otolaryngologist. Blood samples were taken and also urine, which were sent to the Rochester Mayo Clinic for very specific tests – checking for autoimmune diseases, diabetes and encephalopathy.
After all test results were in, my diagnosis was determined. I don't have diabetes or an autoimmune disorder, so my Autonomic Neuropathy is deemed "idiopathic". My symptoms are being treated by medication and it has helped tremendously. I no longer battle dizziness/vertigo and fainting to the ground. My blood pressure stays at a healthy level now, during the day.
I wish you the very best and hope you see a Neurologist soon, who will help you.