If you’ve never heard of catamenial epilepsy¹, you certainly aren’t alone. This is condition is a gender-specific type of epilepsy that occurs only in women and is associated with the menstrual cycle.
Catamenial epilepsy is not a new phenomenon, yet it has not been studied enough for us to determine exactly why it occurs and how to treat it.
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The official and technical definition of catamenial epilepsy² is “a pattern of seizures that changes in severity during particular phases of the menstrual cycle, wherein estrogens are proconvulsant, and progesterone is anticonvulsant”.
What this rather convoluted definition means is a woman with epilepsy experiences changes in severity according to the hormones associated with the menstrual cycle.
Phases of the menstrual cycle with high estrogen mean a person with catamenial epilepsy is more prone to seizures. However, during phases with high progesterone, they are less likely to experience seizures.
Catamenial seizures are actually quite common, affecting between 10% and 70% of fertile women. The reason for this disparity is simple: researchers do not agree on how to define the association between seizures and the menstrual cycle.
Generally, to be diagnosed with catamenial epilepsy, a person has to keep track of their seizures and menstrual cycle. If they’ve been officially diagnosed with epilepsy (often through electroencephalogram (EEG)³, their doctor may then study their menstrual cycle to identify a link between their cycle and the severity of their seizures.
However, a large number of epileptic patients simply do not know what causes their seizures. As such, finding out whether the seizures are associated with the menstrual cycle or with another coincidental factor can often be difficult.
To add another layer of difficulty, diagnosis relies on patients keeping excellent records of their menstrual cycles and epileptic seizures without accidentally changing or biasing their observations. Unfortunately, this isn’t always the most reliable system.
These factors mean that it’s very difficult to determine what percentage of fertile women experience catamenial seizures. We simply don’t have a reliable way to test for this condition, despite it being around since ancient times.
The current diagnostic criteria⁴ require the combined seizure/menstruation diary to show that the number or severity of seizures at least doubles during one phase of the menstrual cycle for two consecutive menstrual cycles. Only then can catamenial epilepsy be suspected.
Seizures in catamenial epilepsy are no different from seizures in other forms of epilepsy, except that the frequency and severity of the seizures are associated with a particular phase of the menstrual cycle.
Catamenial seizures⁵ can be generalized, which means they affect both sides of the brain and cause jerking and loss of consciousness, or focal (partial), meaning that they occur in one spot in the brain and present as vacant staring or sudden confusion.
This pattern of catamenial epilepsy is associated with the perimenstrual period, which sees an increase in the number of and severity of seizures during the menstrual phase. This is thought to be caused by a sudden loss of progesterone and estrogen.
Seizures can become more common in the ovulatory phase of the menstrual cycle. These seizures are thought to be associated with high levels of estrogen and low levels of progesterone. As estrogen is pro-seizure and progesterone is anti-seizure, the changes in their levels increase the frequency and severity of seizures in ovulating women.
Seizures can also occur in the luteal phase of the menstrual period. When seizures increase in number and severity during this period, it’s thought to be because low levels of anti-seizure progesterone are circulating, increasing the frequency and severity of seizures in some women.
Currently, treatment options for catamenial epilepsy are lacking because we don’t know enough about this condition. As you can imagine, this can be quite difficult to study as a large enough group of people who are willing to participate and who routinely have seizures that increase in frequency and severity during menstruation can be hard to find.
Many catamenial seizures can’t be treated with medicine. They’re either drug-resistant or incurable, so attempted treatments often lead to a worse quality of life for the women involved. The most common treatment for these seizures is hormone therapy, which only controls the underlying cause.
The cause of catamenial seizures is the menstrual cycle. These seizures aren’t caused by conditions like stroke, or brain injury, which can cause epilepsy in some people. Rather, catamenial seizures are a result of the changes in hormones that occur over the menstrual cycle.
During a woman's menstrual cycle, the hormones that cause a period can also cause changes in their brain. This is because the hormones that cause a menstrual cycle are known as neuroactive hormones, meaning they impact the brain.
The two main hormones involved in menstruation are estrogen and progesterone. We don’t know very much about how estrogen and progesterone work in the brain, although both of these hormones have been widely studied as part of the menstrual cycle. Therefore, researchers remain uncertain as to how to prevent seizures in women with catamenial epilepsy.
It seems reasonable to believe that if a menstrual period is responsible for catamenial epilepsy, then menopause⁶, or the loss of menstruation, would cure catamenial epilepsy. The hormones controlling menopause are also complex, and researchers simply haven’t studied these hormones enough to say. Therefore, this theory remains unproven.
Catamenial seizures are caused by hormonal activity during the menstrual cycle. Hormones including estrogen and progesterone can cause either generalized or focal seizures that are generally resistant to anti-seizure medications.
Therefore, the most common treatment for catamenial seizures is hormone therapy. However, there is still much to learn about the condition, and research continues.
Catamenial epilepsy | Cedars Sinai
Basics about catamenial epilepsy | Epilepsy Foundation