Vasovagal response
| Vasovagal syncope | |
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| Synonyms | Vasovagal episode, vasovagal response, neurocardiogenic syncope |
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| Vagus nerve | |
| Specialty | Neurology, cardiovascular |
| Classification | |
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| External resources |
Vasovagal syncope is loss of consciousness mediated by the vagus nerve. Vasovagal syncope is the most common type of fainting. Vasovagal syncope is most commonly found in adolescents and in older adults.
There are different syncope syndromes which fall under the umbrella of vasovagal syncope. The common element among these conditions is the central mechanism which may lead to the loss of consciousness. The differences among them are in the factors that trigger this mechanism.
Episodes of vasovagal syncope are typically recurrent and usually occur when the predisposed person is exposed to a specific trigger. Prior to losing consciousness, the individual frequently experiences early signs or symptoms such as lightheadedness, nausea, the feeling of being extremely hot or cold (accompanied by sweating), ringing in the ears (tinnitus), an uncomfortable feeling in the heart, fuzzy thoughts, confusion, a slight inability to speak or form words (sometimes combined with mild stuttering), weakness and visual disturbances such as lights seeming too bright, fuzzy or tunnel vision, black cloud-like spots in vision, and a feeling of nervousness can occur as well. The symptoms last for a few seconds before the loss of consciousness (if it is lost), which typically happens when the person is sitting up or standing.
When sufferers pass out, they fall down (unless prevented from doing so) and, when in this position, effective blood flow to the brain is immediately restored, allowing the person to regain consciousness. If the person does not fall into a fully flat, supine position, and the head remains elevated above the trunk, a state similar to a seizure may result from the blood's inability to return quickly to the brain, and the neurons in the body will fire off and generally cause muscles to twitch very slightly but mostly remain very tense. Fainting occurs with a loss of oxygen to the brain.
The autonomic nervous system's physiological state (see below) leading to loss of consciousness may persist for several minutes, so
Vasovagal syncope occurs in response to a trigger, with a corresponding malfunction in the parts of the nervous system that regulate heart rate and blood pressure. When heart rate slows, blood pressure drops, and the resulting lack of blood to the brain causes fainting and confusion.
Typical triggers for vasovagal episodes include:
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