An Overview of Rasmussen's Syndrome

The condition often involves Rasmussen's encephalitis

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Rasmussen's syndrome is a multi-stage, chronic neurological disease that often includes Rasmussen's encephalitis—an inflammatory stage that usually affects only one side of the brain. The syndrome itself is a continuation of symptoms even after the inflammation is gone. This disease is rare, with fewer than 2,000 people in the United States believed to be living with it. In most, it begins before age 10.

Symptoms of Rasmussen's Syndrome
Verywell / JR Bee


Rasmussen's syndrome is the term used to describe the condition at any time during the course of the illness. It is believed that Rasmussen's syndrome may sometimes be caused by or preceded by a type of inflammation of the brain called Rasmussen's encephalitis.

Rasmussen's syndrome is a long-lasting medical condition that can persist for years after the most intense stages of this inflammation have subsided. In some cases, Rasmussen’s syndrome can occur without confirmation of Rasmussen’s encephalitis having come before it at all.

In the encephalitis phase, the brain has a very strong autoimmune reaction that causes severe disruption of brain function on one side.

Symptoms are the same regardless of the phase. They include:

  • Seizures, often predominantly affect one side of the body
  • Weakness, usually on one side of the body
  • Language problems
  • Cognitive deficits (thinking and problem-solving difficulties)

Generally, the seizures caused by Rasmussen's encephalitis are difficult to control with medication. The seizures are usually associated with shaking and jerking. A decrease in or loss of consciousness also often occurs.

If you have Rasmussen's encephalitis, you might not remember the seizures in detail, and you might feel exhausted afterward. Weakness, language problems, and cognitive difficulties often start to occur months after the seizures begin, but these symptoms may occur sooner or not at all. In some, they can become severe.


This condition most commonly affects children ages 2 to 12, but can affect people of any age. While it's unclear what the exact cause of Rasmussen’s encephalitis is, the medical community has considered two main possibilities:

  • An infection that triggers a severe immune reaction
  • An autoimmune reaction (the body attacking itself)

As researchers have learned more about this disease, they've found compelling evidence backing up the autoimmune theory. At the very least, research appears to show that Rasmussen's involves at least some autoimmune activity, with specialized immune cells invading and attacking one side of brain.


It may take a long time to get a definitive diagnosis of Rasmussen's. This is because there is no simple test to confirm it.

Rasmussen's encephalitis and Rasmussen's syndrome are diagnosed based on your doctor’s observations of your clinical symptoms over months (or even years) along with electroencephalogram (EEG) and brain magnetic resonance imaging (MRI) testing.

An EEG is expected to show seizure activity on one side of the brain. But this EEG pattern is not unique to Rasmussen’s syndrome, so the test is not definitive. Results are considered in conjunction with your symptoms, other tests, and your doctor’s observations of your condition.

A brain MRI is expected to show a significant difference between the two sides of the brain. Early in the course of the illness, one side of the brain may show an inflammatory pattern that looks like an infection.

Later in the course of the illness, the brain MRI may show atrophy of the affected side, which is actually shrinking of the brain due to the prolonged damage from the inflammation. This brain MRI appearance is not unique to Rasmussen’s encephalitis or Rasmussen’s syndrome either, so this, too, will be considered along with other factors in order to reach a formal diagnosis.


There is no cure for Rasmussen's. The main treatment option is anti-seizure medication. Sometimes, steroids are used to decrease inflammation in the brain. If your medical team has reason to believe that you have a neurological infection (infectious encephalitis), then you may receive medication to target the infection as well.

If you have seizures, weakness, or any other neurological deficit but no evidence of inflammation, then your treatment is largely going to target your seizures and neurological deficit.

Sometimes, the epilepsy of Rasmussen’s syndrome is so severe that you or your child may need to have epilepsy surgery. This surgery could involve removing the affected region of your brain, especially if that region appears to be causing much of the damage.

Often, the surgical procedure causes lasting side effects, such as partial or complete weakness of one side of the body.

Surgical intervention for Rasmussen’s syndrome should be very carefully deliberated, and it is only an option if it is expected to improve your overall quality of life.


Dealing with the changes forced on you and your family by Rasmussen's disease can pose some challenges. Reach out to your child's school to see what support and resources may be available to you. Let them know about any cognitive changes your child may be undergoing and make sure the staff knows how to handle a seizure if one should happen at school.

A support group can be a big help, as well. You might be able to get advice and learn through shared experiences. Plus, it can help just to know other people understand what you're going through.

This disease, especially in a child, can impact the entire family. If you're having trouble dealing with any aspect of it, don't hesitate to see a mental health counselor.

A Word From Verywell

When all you want is to keep something from getting worse and for things to be back to normal, it can be difficult to hear doctors tell you that's not possible. The best things you can do to feel more empowered is to educate yourself about the disease and to try to have realistic expectations about treating and managing it.

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