New guideline: Blood test can help determine type of seizure

Using a blood test to measure the level of the hormone prolactin can help determine, in certain clinical settings, whether an epileptic seizure has occurred, according to a guideline developed by the American Academy of Neurology and published in the September 13, 2005 issue of Neurology. The guideline authors reviewed all of the scientific evidence available on use of the prolactin blood test to diagnose seizures and developed evidence-based recommendations.

The blood test, which must be used within 10 to 20 minutes after a seizure, can identify the types of seizures called generalized tonic-clonic seizures and complex partial seizures in both adults and older children. The level of prolactin in the blood increases after these types of seizures occur.

The release of prolactin from the pituitary gland is controlled by the area of the brain called the hypothalamus. Researchers have hypothesized that epileptic seizures may affect the hypothalamus, altering the release of prolactin.

The test cannot distinguish epileptic seizures from a fainting condition called syncope, because prolactin levels may also increase after syncope, according to guideline authors David K. Chen, MD, Yuen T. So, MD, PhD, and Robert S. Fisher MD, PhD, of Stanford University in Palo Alto, Calif.

The guidelines found that a prolactin test can be useful in differentiating epileptic seizures versus psychogenic seizures, or seizures caused by mental problems.

There was not enough evidence to determine whether the prolactin test is useful in evaluating cases of status epilepticus, repetitive seizures, or neonatal seizures.

The guidelines state that the test is useful as an adjunct test, especially in cases where video EEG (electroencephalography) monitoring is not readily available. Future research needs to be done to determine whether the test is valid for younger children.