Autonomic Disorders Consortium

Information for Patients and Families

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Neurally Mediated Syncope (NMS)

What is Neurally Mediated Syncope (NMS)?

Syncope (described as “fainting” or “passing out”) is a common problem, accounting for approximately 3% of emergency room visits. Neurally mediated syncope (NMS) is also called neurocardiogenic, vasovagal, vasodepressor or reflex mediated syncope.

Repeated episodes of NMS may be caused by a wide variety of medical problems, and require diagnosis and treatment. It is important to distinguish syncope from “dizziness”, which generally refers to an alteration in balance, vision, or perception of the environment, without the loss of consciousness.

What causes NMS?

Neurally mediated syncope occurs when the part of the nervous system that regulates heart rate and blood pressure malfunctions, often in response to a trigger. The heart rate slows, and the blood vessels in the legs widen. This allows blood to pool in the legs, which lowers blood pressure. The drop in blood pressure and slowed heart rate quickly cause diminished blood flow to the brain, causing fainting.

How is NMS diagnosed?

The diagnosis of neurally mediated syncope often focuses on ruling out other potential causes of fainting - particularly heart-related problems. Tests may include:

What is the treatment for NMS?

In many cases, education about ways to avoid “triggers” may be enough to control NMS.

Treatment may require medications, therapies to increase blood pressure or decrease pooling of blood in the legs or the use of an electrical pace maker to regulate heartbeat. Other therapies include using compression stockings, sleeping with the head of the bed slightly elevated, and mild aerobic conditioning (especially in the water).