Pediatric anti-NMDA receptor encephalitis

What is pediatric anti-NMDA receptor encephalitis?

In this form of encephalitis, the body makes antibodies that bind to proteins on the NMDA receptor. NMDA receptors are located on the outer surfaces of cells called neurons and are important to brain function.

This misdirected immune response causes inflammation and swelling in the brain (encephalitis). The NMDA receptors help neurons communicate. An immune response directed at these receptors can affect thinking, memory, mood, consciousness and breathing. These symptoms can be very serious and get worse over time.

Risk factors

This form of encephalitis affects about one in 1.5 million people. It affects females and males but is more common in females.

What are the signs and symptoms of pediatric anti-NMDA receptor encephalitis?

Symptoms can depend on factors such as a child’s age and which parts of the nervous system are affected. At first, a child may experience milder symptoms, including a fever and subtle changes to mood or thinking. Later, they may develop more severe symptoms such as seizures and lethargy and need to be hospitalized.

Your child may experience:

• Flu-like symptoms

• Seizures

• Changes in thinking (cognition), speech and memory, including confusion and short-term memory loss

• Behavior changes, including irritability, aggression and sleep disorders

• Movement disorders, including rhythmic movements of arms and legs and unusual motions of the mouth and face

• Psychiatric symptoms, including hallucinations and psychosis

How is pediatric anti-NMDA receptor encephalitis diagnosed?

The diagnosis for this encephalitis is confirmed by a blood or spinal-fluid test, or both. These tests can detect the antibodies that attack the NMDA receptors. It can take several weeks for doctors to receive your child’s test results.

Starting treatment early makes a big difference in how a child recovers from this disease. While we wait for the test results, we will try to rule out other conditions, such as infections, metabolic diseases, psychiatric disorders and other inflammation in the brain.

We will also use other tools to try and diagnose your child so we can start treating them as soon as possible.

Our diagnostic approaches could include:

• MRI (magnetic resonance imaging) - Looks for changes in their brain

• Neurologist - Physical exam

• EEG (electroencephalogram) - Monitors the electrical activity in your child’s brain

What are the causes of pediatric anti-NMDA receptor encephalitis?

This type of encephalitis was identified fairly recently, and doctors still aren’t completely sure what causes it. There likely are a variety of genetic and environmental triggers. Doctors and researchers are working hard to understand what they might be. In some cases, an infection or a tumor can set off an immune response that mistakenly attacks the NMDA receptors.

How is pediatric anti-NMDA receptor encephalitis treated?

We see children with this type of encephalitis every year, giving us the experience to recognize and treat this condition. We will use different therapies to suppress the immune system and limit the damage that encephalitis can cause.

In the beginning, therapies usually include:

• High-dose steroids reduces inflammation

• Plasma exchange/plasmapheresis (PLEX) is the most effective treatment in a hospital setting. Like dialysis, this process can clean your child’s blood of the antibodies it carries. Children’s Health has the specialized equipment to treat your child with PLEX, and we often administer it more quickly than other hospitals. This may give your child the opportunity to get better faster.

• Intravenous immunoglobulin (IVIG) consists of antibodies from the purified blood plasma of healthy donors. IVIG can reduce inflammation and affect the creation and destruction of the disease-causing antibodies.

• Surgery removes the tumor in children whose encephalitis was triggered by a tumor.

For children who do not respond to the initial treatment or need longer-term treatment, therapies include:

• Rituximab® targets the antibody-producing cells and is often used in other autoimmune diseases.

• Cyclophosphamide works by slowing or stopping the immune cell response and is often used in cancer therapy.