Department of Neurology

EEG and seizures during menstrual periods

Q: I have had 2 normal EEG's in the past 2 years. However,once I was weaned off of my medication (1000mg of Tegritol) I experienced another seizure. Looking back in retrospect we have realized that every seizure I have experienced have been during my period or a day or two before. In the two normal EEG's that I had, I was in the middle of my cycle and not near a period. Do you think that there is a possible connection?

A: The electroencephalogram, or EEG, is a very useful tool for your doctors to help verify epilepsy, and determine which medications can be used. However, a normal EEG does not exclude epilepsy, and an abnormal one does not necessarily mean you have epilepsy. Since an EEG only records about 45 min of brain activity, it is common for persons with epilepsy to have a normal EEG. Sometimes the only abnormalities are seen during an actual seizure.

Many women note that their seizures are worsened or occur only during their menstrual period. This has been termed "catamenial epilepsy." In addition to seizure medicines, hormonal therapy is sometimes used for persons who do not respond well to seizure medications, with varying degrees of success.

Unfortunately, the EEG is not entirely predictive of whether someone can come off of medications. Most epileptologists feel more secure about reducing medications in a person who has been seizure free when the EEG is normal. However, as you have experienced, a normal EEG does not guarantee a successful wean from medication.

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