Acute Necrotizing Encephalopathy

Acute necrotizing encephalopathy (ANE) is a rare but serious condition that causes brain damage following a viral infection, most often influenza (the flu). ANE primarily affects children and causes inflammation and swelling in the brain, which can lead to severe neurological symptoms and long-term damage, particularly to the thalamus. The thalamus is a key part of the brain involved in sensation and movement.

While inflammation is a normal response to infection, excessive inflammation can damage tissues, including brain cells. In ANE, viruses aren’t found in the brain or spinal cord, so the damage is more likely caused by the body’s immune reaction to the infection rather than the virus itself.

Because ANE can progress quickly, it’s important to recognize and treat it early for the best possible outcomes.

Symptoms of ANE can develop quickly and vary in severity. Early signs often resemble those of the viral infection causing the condition and may include:

• Congestion
• Cough
• Diarrhea
• Fever
• Vomiting

As ANE progresses, more severe symptoms can develop, such as:

• Fainting or loss of consciousness
• Difficulty with movement or coordination
• Seizures
• Trouble breathing
• Liver problems

Although the exact cause of ANE hasn’t been fully determined, doctors do know that it’s usually triggered by a viral infection. People with changes in the RANBP2 gene may be more likely to develop ANE because this gene helps move materials in and out of cells. When altered, the protein it makes doesn’t work correctly, making it harder for brain cells to function — especially when fighting off a virus.

Influenza is the most common virus that triggers ANE, but other viruses, including SARS-CoV-2 (which causes COVID-19), HHV6 (which causes roseola, also known as sixth disease, and is associated with high fever in babies and toddlers), adenoviruses, and enteroviruses, are also linked to the condition.

Diagnosing ANE usually involves:

• A physical exam and medical history review: Your child’s doctor will ask about symptoms and recent infections.
• An MRI to identify areas of brain damage and swelling
• A CT scan to quickly rule out other conditions, especially if an MRI isn’t possible or a faster assessment is needed
• Blood tests to identify infections or signs of inflammation
• A lumbar puncture to test cerebrospinal fluid for infection

Treating ANE mainly focuses on managing symptoms and preventing further brain damage. Common treatments include:

• Antiviral medications if a specific virus is identified
• Steroids or immune-suppressing medications to reduce brain swelling and inflammation
• Seizure medications to control seizures and protect brain function
• Rehabilitation such as physical, occupational, and speech therapies to help your child regain strength and ability

The long-term outlook for children with ANE can vary. Some children fully recover, while others may experience lasting effects, such as:

• Developmental delays
• Seizure disorders
• Difficulty with movement or coordination
• Cognitive or behavioral challenges

The earlier ANE is diagnosed and treated, the better the chances for minimizing long-term effects. While ANE is a serious condition that can be life-threatening, prompt treatment can improve outcomes and reduce complications. A child may need rehabilitation therapy to help recover and adjust to any lasting impacts.

At Boston Children’s Hospital, we take a team-based approach to treating ANE. Our neuroimmunologists, neurologists, infectious disease experts, rehabilitation therapists, and other specialists work together to provide comprehensive and personalized care for your child.

We used advanced diagnostic tools to carefully assess the severity of ANE and develop a tailored treatment plan for your child. Their plan could include immediate care to manage brain inflammation and long-term rehabilitation to help them regain cognitive and physical abilities.

We work closely with you and your child to support their recovery and ensure the best possible outcome.