In all of these conditions, upright
posture makes the person sick. Walking and running are actually easier
than standing or sitting still.
The symptoms caused by standing or sitting may include any of the following: fainting, dizziness, nausea, feeling very tired, feeling excessively jittery, having difficulty concentrating or remembering things, experiencing pain in the lower parts of the abdomen or in the legs, mottling or purpling of hands, ankles, feet and legs, hot flushes, sweating, and headache.
The underlying cause is a disruption of the autonomic nervous system. This system automatically regulates bodily functions, including heart rate and blood pressure. It also responds to postural or orthostatic stress. Blood is a liquid. It tries to flow downward. When you are standing it tends to run into your legs and feet. This deprives your upper body and, especially, your brain, of an adequate blood supply. The autonomic nervous system prevents this by regulating how the heart beats and by constricting blood vessels in the lower parts of the body, forcing blood upward. In people with COI, this system doesn't work right and blood tends to pool in the belly, legs, and feet. It will pool in the hands, too, if the arms are dangling. This is what causes the mottling or purpling of the skin usually seen in COI..
When the blood pools in the lower parts of the body, the heart tries to compensate by beating more rapidly. But because the blood isn't flowing correctly to the heart and brain, efficiency drops and things get worse. In many cases this leads to a sudden drop in blood pressure, which may cause severe symptoms and even fainting.
The fast heart beat typical of upright posture in COI is called "tachycardia." This is why the condition is often called Postural Tachycardia Syndrome. Low blood pressure is called hypotension.
Most people with COI have normal blood pressure when it is taken in a doctor's office. The sudden drop in pressure typical of NMH can only be detected when it happens--after the person has been standing or sitting quietly for a period of time (several minutes to an hour or more). By the time this happens the person is already feeling sick--dizzy, tired, or in pain--from postural stress.
Many people with severe COI have Chronic Fatigue Syndrome too. And those with CFS frequently (but not always) have COI. I don't know why this is. And nobody knows what causes COI itself (though it does often getting suddenly worse following a viral infection). Other associated conditions are Fibromyalgia, Ehlers-Danlos Syndrome, ovarian and pelvic (internal) varicose veins, varicocele, and Chiari I Malformation and/or cervical stenosis. Information about these conditions can be found in the links just given and in the brief descriptions at the end of page.
If you don't have any of these complicating conditions, you can detect COI yourself, and taken measures to help it. My discussion of this is here.
There are many online resources that discuss these conditions in detail, and about how they can be treated medically. I particularly recommend the description of the experience of COI by the soccer star, Michelle Akers. These links are also useful:
Fainter's United is a social support group for autonomic disorders such as POTS/OI/NMH, NCS, dysautonomia or similar syndromes. The club sponsors regular chats and has a message board.
Postural Orthostatic Tachycardia Syndrome gives an excellent overview of dysautonomia and is particularly strong in explaining cervical stenosis and Chiari Malformation. It has a number of excellent links on these topics.
The National Dysautonomia Foundation
Robyn's Neurally Mediated Hypotension Pages have many other links.
Some Complicating Conditions (there may be others):
Ehlers-Danlos Syndrome is an inherited condition in which many tissues in the body (often including blood vessels) are fragile and overly stretchy. Symptoms are variable and often almost undetectable but people with well defined EDS often can bend their bodies into odd positions, easily dislocate joints, have fragile skin with wide scarring, and have other symptoms.
Chiari I Malformation. Chiari malformation is a narrowing of the base of the skull near where the brainstem and the spinal cord emerge into the cervical spine. This puts pressure on portions of the lower brain, causing a complex symptom picture. Chiari II is seen in spina bifida, a disabling condition present at birth . Chiari I often causes no symptoms and may be unsuspected until adulthood. Symptoms may beginning slowly for no apparent reason, or may come on rapidly following head trauma or injury to the neck. The symptoms may mimic, or be exacerbated by, cervical stenosis (narrowing of the interior of the vertebral column in the region of the neck, which puts pressure on the spinal cord).
Varicocele is enlargement of the veins that drain the testicles. Usually it causes no harm but it can infere with fertility and in a person with marked venous pooling may be very painful.
Ovarian and pelvic varices (varicose veins) often occur in women who have had children, and are frequently the cause of pelvic pain and painful intercourse. Usually they are undetected and the pain is thought to be "psychosomatic." When detected, the condition is often called "pelvic congestion syndrome." In persons with marked venous pooling these varices are often particularly painful.
See above for links to these conditions.
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