Overview of Rasmussen's Syndrome and Rasmussen's Encephalitis

A rare seizure disorder

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Rasmussen's syndrome is a multi-stage chronic neurological disease that often includes Rasmussen's encephalitis. Rasmussen's encephalitis is 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 U.S. believed to be living with it. In most, it begins before age 10.


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.

This is a long-lasting medical condition that can persist for years after the most intense stages of inflammation of Rasmussen’s encephalitis. Sometimes Rasmussen’s syndrome can occur even if it is unclear whether Rasmussen’s encephalitis preceded it.

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 for the encephalitis and the syndrome. They include:

  • Seizures that may be hard to control
  • 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, and often predominantly affect one side of the body. The seizures are usually associated with shaking and jerking of one side of the body, often with loss of consciousness or a decrease in consciousness.

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 between the ages of 2-12 years old 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:

  1. An infection that triggers a severe immune reaction
  2. 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 encephalitis. This is because there is not a simple test to confirm this condition.

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 EEG testing and brain 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, and therefore an EEG is not a definitive test, but is used in correlation with your symptoms, your 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, and is considered along with the whole situation in order to reach a conclusion that you have this disease.


The main treatment for Rasmussen’s is anti-seizure medications. 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 poses some challenges.

Reach out to your child's school to see what support and resources may be available to you, as well. 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

Rasmussen's can be scary. You likely want something to keep it from getting worse and return your child to their previous functional levels but have doctors telling you that's not possible.

Rather than focusing on a cure that doesn't exist, educate yourself about the disease and try to have realistic expectations about treating and managing it. That will be far more helpful for you and your child.

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