For the first time, scientists report an instance of a brain seizure making someone believe they underwent a sex transformation.

The case in question involved a 37-year-old woman admitted to an epilepsy center in Germany for seizures in 2006. In addition to instances of nausea, fear, and sometime déjà vu several times a week, she reported occasionally also perceiving the following delusion:

"I'm no longer feeling to be a female," the scientists reported her saying. "I have the impression to transform into a male. My voice, for example, sounds like a male voice that moment. One time, when I looked down to my arms during this episode, these looked like male arms including male hair growth."

Even stranger, this delusion was not limited to only herself. She also saw nearby women as becoming men too. "One time another woman, a friend of mine, was in the same room, I perceived also her as becoming a male person including changing sound of her voice," the scientists reported her saying.

Prior to these delusions, the woman was completely healthy with no history of any other mental disorders, other than symptoms of depression in her later adulthood. "The patient never experienced a similar phenomenon outside the seizures," explained researcher Burkhard Kasper, a neuroscientist at the University of Erlangen in Germany. Anticonvulsive drugs later relieved her of these delusions and most of her other symptoms.

MRI scans revealed a tumor in the woman's brain that was apparently linked with the seizures. The kind of tumor in question, a ganglioglioma, is generally considered benign. "We expect her to have a long life," Kasper said.

The tumor is located in the right amygdala, with irregular activity seen in the surrounding right temporal lobe. The amygdala seems to play an important role in processing human identity, including aspects like familiarity, emotional state, and sex, and past studies revealed that electrical stimulation of the temporal lobe triggered doubt about sexual identity.

These findings suggest that brain circuits linked with perception of gender exist in the brain.

Although this is so far an isolated case, "neuroscience has learned a lot from single patients," Kasper mentioned, pointing out cases such as "HM," or Henry Molaison, a man whose inability to commit new events to long-term memory after brain surgery for epileptic seizures helped revolutionize science's understanding of how memory works.

In seizure patients, brain surgery is sometimes used to implant electrodes that not only can help monitor and control the disorder, but also can stimulate cells to better understand brain circuits. While it might be ideal to use such electrodes to probe the unusual delusions seen in this woman, surgery of any kind is not called for at the moment, since drugs help keep her seizures well under control, Kasper said.

Instead, the researchers seek to develop tests checking how well a person can distinguish gender, to both analyze this patient and potentially others. Advanced brain imaging techniques might also shed light on these circuits, Kasper added.

The scientists detailed their findings online August 19 in the journal Epilepsy & Behavior.