What you need to know about Neurally Mediated
Hypotension and Chronic Fatigue Syndrome

Q: What is neurally mediated hypotension??

A: Neurally mediated hypotension (NMH) is a condition in which the body has difficulty regulating the blood pressure, especially when one is upright. There seems to be a misconnection between the brain and the nerves that control the blood pressure and heart rate. The reason is unknown.

Q: What happens in this condition??

A: People with this condition experience spells in which the blood pressure drops suddenly, leading to weakness, lightheadedness or dizziness, sweating, vision disturbance and a feeling of fainting or near-fainting. During an episode, some people may get an irresisible urge to sit or lie down or a feeling that something bad may happen if they remain standing.

Q: What is the result of such a spell of low blood pressure??

A: A person suffering spells like this may have prolonged fatigue, weakness, and difficulty with thought, concentration and memory.

Q: Do only people with CFS get NMH??

A: No. It may be seen in people who have no fatigue. And NMH is not seen in all CFS cases, either.

Q: What exactly happens in a spell of NMH??

A: It's a complicated set of events, but basically here's what happens: First, the blood pressure starts to fall. Normally, that would cause the heart to speed up and the blood vessels in the legs to tighten (constrict), leading to a rise in the blood pressure. In people suffering NMH, the fall in the blood pressure causes the heart to slow down and the blood vessels in the legs to loosen (dilate). The result is a much greater fall in the blood pressure. The blood flow to the brain then is sharply reduced and fainting or near-fainting results.

Q: Why do the heart and blood vessels respond improperly??

A: The cause is not currently known.

Q: Is NMH the cause of CFS??

A: Some researchers have claimed that CFS is caused by NMH. However, many physicians who specialize in the treatment of CFS believe that this blood pressure regulation is simply another body system knocked out of kilter by CFS. Although it appears that many CFS patients have NMH, clearly there are many others that do not. More research is needed to clear up this point.

Q: How is NMH diagnosed??

A: Unfortunately, it cannot be diagnosed with simple blood pressure measurements. This condition is not the same as the common momentary dizziness that even many well people get when they arise from a chair or from a bed too quickly. The diagnosis requires a "tilt table test".

Q: What is a tilt table test??

A: Under the supervision of a physician, the patient rests motionlessly on a special table that slow tilts upward to a near-standing position. The patient then remains standing on a footrest with a safety belt in place. Blood pressure and pulse rates are continually monitored by a machine. A positive test occurs if the blood pressure falls along with a sudden drop in the pulse rate.

If this blood pressure does not fall during this phase of the test, a medication to raise the pulse rate is given intravenoulsy. If the blood pressure and the pulse rate fall during this stage of the test, then the test is considered positive as well.

Q: How is NMH treated??

A: Treatment consists of medication that prevents the heartbeat from slowing when it should be speeding up, medication to boost the blood pressure and sometimes a change in the diet to include more sodium (salt). Treatment must be individualized for each patient; there is no standard "one size fits all" dose.

Q: Is treatment always effective??

A: Unfortunately, no. Quite a few patients will feel better overall and some will feel great. In perhaps a third of the patients with this condition, treatment doesn't seem to help at all. Side effects are often a problem to CFS patients (who are ordinarily more sensitive to medications).

Q: Should I just start on a high-salt diet??

A: No. High-salt diets may not be helpful and even *dangerous* for some patients. Proper diagnosis is necessary before such diet modifications are made.

Q: Should every CFS patient get a tilt table test now??

A: No. The research that has been published is limited and we can't draw too many conclusions from it. We are not recommending the test for every CFS patient. We are trying to screen patients based on their medical history and their answers to certain questions. At some point in the future, the tilt table test may possibly become a standard test for CFS but currently it is considered a "special circumstances" test.

Q: Is there any special preparation for a tilt table test??

A: Certain medications may affect the results and should be discontinued under the physicians supervision one to two days before the test. These medications include amitriptyline and other tricyclic antidepressants, beta-blockers, and certain muscle relaxants.

1996, Inter I.D., Tulsa, OK


Johns Hopkins Hospital Report

Blair P. Grubb M.D.


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