Investigators seek cause of persistent 'head rush' disorder
Dr. David Robertson
It's a familiar sensation, one that most people have experienced at one time or another. After standing up quickly, a wave of dizziness briefly washes over your senses, throwing off your balance and leaving you momentarily disoriented.
This so-called 'head rush' doesn't last long, usually just a few seconds. But what if the heart races and the rush persists, not just in duration but in frequency? What if a person becomes dizzy and disoriented every time they stand, for months on end?
That's no ordinary 'head rush,' it's an affliction known as orthostatic intolerance, one of several disorders of the autonomic nervous system currently being investigated at Vanderbilt University Medical Center's Clinical Research Center with the help of a newly funded Program Project Grant (PPG) from the National Institutes of Health.
"These types of grants don't come along very often," said Dr. David Robertson, professor of Medicine and director of the Clinical Research Center. "There are only 14 PPGs currently ongoing at the medical center, so we are very excited about this new opportunity.
"The idea of a PPG is to support a group of investigators with the idea that they can do more together than they could ever do on their own. We've put together a group of investigators with the mission of finding and discovering the pathophysiology of these disorders so we can treat them better. This grant brings together expertise in the departments of Pharmacology, Neurology and Medicine."
While devoted to investigating disorders of the autonomic nervous system, the bulk of the PPG is related to the broad disorder known as orthostatic intolerance. Three basic areas are being targeted for investigation into the causes of orthostatic intolerance ‹ abnormalities in the peripheral systems, or body, abnormalities in the brain and abnormalities in the nerve systems leading to the brain.
Robertson is investigating the peripheral systems. Brain abnormalities are being investigated by Dr. Augustin Rogelio Mosqueda-Garcia, assistant professor of Medicine; and nerve system abnormalities are being investigated by Dr. Italo Biaggioni, associate professor of Medicine.
The problem of orthostatic intolerance has only recently come under close scrutiny. While it can persist for months, and even years, the disorder ‹ which can vary greatly in symptoms and severity from patient to patient ‹ eventually disappears on its own.
"For many years, we didn't really know how serious this problem was," Robertson said. "We knew there were patients with severe orthostatic hypotension whose blood pressure would just plummet when they stood up. They couldn't stand for long before passing out, and they were usually older patients."
But from time to time, a milder disorder would be seen in younger patients, but with one major difference ‹ blood pressure wouldn't fall, though other symptoms, such as palpitations, sweating, dizziness and nausea, were present.
"One of the big problems is that physicians have not been recognizing this. Most patients are otherwise healthy young women, and so the disorder comes in below the radar of many health care works. You can't go and look this up in the medical textbooks because there is no good name for this disorder," Robertson said. "Everyone called it something different.
"It's normal for people to occasionally experience some visual changes and other symptoms when they quickly stand up after sitting or lying down for a long period of time. But when it happens all the time, and keeps getting worse, that would be orthostatic intolerance. The crucial test is the rapid heartbeat which accompanies standing."
Within the last two years, CRC investigators began studying these cases more carefully, looking for patterns and possible causes, Robertson said.
"The bottom line is that it looks like there is a mild amount of abnormal activity somewhere in the autonomic nervous system that is so subtle that it is hard to spot, but it's enough to cause severe symptoms.
"There is something going on in these people. For example, several patients have had a severe viral illness prior to the beginning of the syndrome. Some have had a profound weight loss prior to onset and several have experienced symptoms similar to chronic fatigue syndrome," Robertson said.
It's too early to determine if observations such as weight loss are hints about the cause or merely a byproduct of the disorder, Robertson said. The disorder has only recently been identified, but as of yet, no environmental, regional or geographic commonalities have been identified, although some forms do seem to be genetic.
"We're just beginning our studies, so we've got a long road ahead of us," Robertson said. "But this type of research is very rewarding because it's entirely patient-oriented and gives us the opportunity to really help people."