Vasovagal syncope (also called the simple fainting spell) occurs due to a reflex (often triggered by pain, fright, an upset stomach, or many other things) causing the blood vessels in the legs to dilate. Blood suddenly pools in the legs, the volume of blood returning to the heart is reduced, the blood pressure falls, and the victim loses consciousness. Once he/she becomes supine, gravity allows the blood to return to the heart, and consciousness is rapidly regained. (Here's more information on vasovagal syncope.)
In a 6-year study conducted by investigators at Northwestern University, up to 8% of patients with vasovagal syncope displayed seizure-like activity when they lost consciousness during a tilt table study. These patients underwent extensive neurological evaluations including EEG (electroencephalogram - a study of the electrical signals produced by the brain), CAT scans, and MRI scans, and none proved to have evidence of a true seizure disorder. Their seizure-like movements during syncope are apparently caused by temporary but extremely low blood pressure during the syncopal episode.
Importantly, the investigators noted that many of these patients had inappropriately received the diagnosis of epilepsy prior to tilt table testing. Several had been receiving anti-epilepsy medications (which are ineffective in vasovagal syncope,) and had been given severe driving restrictions based on the incorrect diagnosis of seizure disorder. The study was reported in the September 8, 2003 issue of the Archives of Internal Medicine.
What this means
If you or a loved one has been given a diagnosis of seizure disorder or epilepsy, despite negative EEGs, you should insist on testing for vasovagal syncope. A positive tilt table study may indicate the true diagnosis, and lead to more appropriate treatment.Sources:
Passman R, Horvath G, et al. Clinical spectrum and prevalence of neurological events provoked by tilt table testing. Archives of Internal Medicine . 2003;163:1945-1948.
