In Netflix's new movie, Brain on Fire, Susannah Cahalan (Chloë Grace Moretz) is a writer who suddenly begins to go through a series of strange experiences — hallucinations, erratic behavior, being in a trance — until she suffers a seizure and ends up in the hospital, waking up with no memory of the previous month. It sounds like something out of a soap opera, but it's a true story, based on the memoir of the same name by Cahalan herself, chronicling what she went through when she was diagnosed with a condition called anti-NMDA receptor encephalitis.
It's a complicated name for an equally complicated illness, but in simple terms, think of your brain as a big computer, with one of the switches in that computer being the NMDA receptor.
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"Everybody’s brain has billions of these things, and [each receptor] functions in order for you to think, learn, and to control your emotions," says Eric Lancaster, MD, PhD, assistant professor of neurology at the University of Pennsylvania.
Anti-NMDA receptor encephalitis, then, happens when an otherwise healthy person's immune system makes a mistake, and starts making antibodies that affect this receptor. In other words, the immune system recognizes an infection and tries to fight it off, but in working overtime to fight that infection, reacts with proteins in the body that attack the brain.
Though Dr. Lancaster says it's an extremely rare disease (there's not much data on how many people actually suffer from it), when it does happen, it often occurs in young women in their teens and early twenties who have an ovarian tumor.
"In about half of patients, there's a tumor on the ovaries called the ovarian teratoma that has NMDA receptors in it, and seems to be the thing that aggravates the immune system," he says. And, when the immune system tries to attack the cells in the tumor, then, it goes into overdrive.
"The body is recognizing that something’s wrong, so it'll start to attack the cells, but unfortunately the body’s now gotten into the habit of attacking the cells, and the antibodies attacking the tumor might actually cross react with certain parts of the body like the brain," says Scott Hirsch, MD, professor of neurology, psychiatry, and child and adolescent psychiatry at NYU Langone Health.
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That being said, young women aren't the only ones who suffer from anti-NDMA receptor encephalitis — men and boys and anyone without ovarian tumors can also get it, though Dr. Lancaster says that doctors aren't 100% certain why.
When someone does get it, Dr. Hirsch says they might start experiencing flu-like symptoms like feeling sick and sluggish. Then, they might develop psychological symptoms like hallucinations, delusions, and agitation, and eventually, epileptic seizures. Because the initial symptoms could be attributed to the flu, or later on, mental health problems, anti-NDMA receptor encephalitis can be hard to pin down at first.
"It can be difficult to diagnose because it looks like other things," he says. "It’s really when the neurological signs develop over the next few weeks that it’s diagnosed. We don’t expect people who have depression to suddenly start having epileptic seizures or become so confused that they can't do their usual functioning. It may be hard for them to get out of bed, but they should be able to do math, let’s say."
However, once the condition is identified, most patients have a big success rate in treatment, which usually involves immune therapies that get the immune system to stop making the antibodies that attack the brain.
"Most patients improve considerably on treatment," Dr. Lancaster says. "The disease has a couple percent mortality rate because it’s dangerous to have bad seizures, to be in the ICU, to stop breathing potentially in a situation where [the patient is] not monitored. There certainly are a few patients who don’t improve despite our best efforts, but the average patient improves a great deal slowly over months. "