Dear Dr. Komaroff: I have a friend with epilepsy. Can you explain what happens in her brain?

Dear Reader: Epilepsy causes repeated seizures. These seizures are caused by sudden, brief changes in the brain’s electrical activity. Our brains have hundreds of billions of cells. The ones that do the work – the ones that help us to think, remember, see, hear, smell, feel and cause us to move – talk to each other through electrical and chemical signals.

What happens in the brain when someone has a seizure is an electrical firestorm. Brain cells fire uncontrollably at up to four times their normal rate.

The kind of seizure that you most often see – on television or in movies – is a generalized, grand mal seizure. It’s very dramatic: A person loses consciousness, falls to the ground and temporarily stops breathing. All body muscles tense up at once for a few seconds; the head and shoulders bend backward. Then, just as suddenly, the arms and legs start jerking and sometimes the face starts twitching. After a few minutes, the person wakes up. However, he or she can be confused and “out of it” for several hours thereafter.

But seizures can be more subtle. A person might just stare blankly and blink their eyes. Nothing is getting through; you can’t reach them. Or a person might suddenly have uncontrollable jerking of one side of the body and a brief loss of awareness of the world. After a seizure, a person has no memory of the episode.

For most people, seizures can be controlled with medication. If you are with your friend when she has a seizure, call the doctor. A seizure that lasts more than 20 minutes is a medical emergency.

What causes seizures in the first place? We know, for example, that brain scars, tumors or infections can cause seizures. But how they cause the electrical firestorm remains uncertain.