When the Immune System Attacks the Brain

What Is Autoimmune Encephalitis?

Published December 2019

Your immune system protects you. It detects germs that could make you sick and attacks them with antibodies. In autoimmune diseases, your immune system attacks a part of your body by mistake. In rheumatoid arthritis, the immune system attacks the joints. In inflammatory bowel disease, the immune system attacks the gastrointestinal tract. In autoimmune encephalitis (AE), the immune system attacks the brain.

“Autoimmune encephalitis is a rare condition that we’re still learning much about,” says Northwestern Medicine Physician Farzaneh A. Sorond, MD, PhD, who specializes in neurocritical care and vascular neurology. “Currently, we know about around 20 antibodies that cause the disease, but the more cases that we see, the more we learn, the more antibodies we discover, and the better we become at diagnosing and treating the disease.”

Symptoms

Common symptoms of AE fall into two categories:

Seizures. This is the most common reason someone with AE will end up in a neurological intensive care unit.
Behavioral issues and cognitive changes, ranging anywhere from memory loss to hallucinations and catatonia.

“Symptoms can be very mild initially, but can quickly progress into seizures that won’t stop,” says Dr. Sorond. “Even 10 years ago, before we knew much about this disease process, mortality rates were very high.”

AE currently has a 6 percent mortality rate.

Neurocritical Care and a Multidisciplinary Approach

“Successful treatment requires a multidisciplinary approach because the way we treat the symptoms of AE, such as seizures, and the potential cause of AE, such as an overactive immune system, often lead to secondary medical complications and co-morbidities,” says Dr. Sorond. “It becomes a fine balance — involving many experts — based on experience, symptoms and the individual we’re treating.”

The brain controls everything. When it’s under attack as it is in AE, it can negatively affect almost every organ system. That’s why AE treatment must involve an array of specialists from neurointensiveists, eplipetologists, infectious disease experts, psychiatrists, immunologists, pulmonologists, hepatologists, rheumatologists and many more.

Treatment is challenging and requires a multidisciplinary approach.

— Farzaneh A. Sorond, MD, PhD

Recovery takes time. A study of 577 patients with one type of AE, who were treated with immunomodulation therapy, reported that 81 percent had a substantial or complete recovery. On average, these patients took roughly 14 months after the acute onset of AE before seeing improvement.

Long-Term Management

Once a patient with AE leaves critical care, they will typically begin rehabilitation to address any cognitive or motor complications — the “sequela of the acute episode,” as Dr. Sorond puts it. Patients will continue to see a neurologist and immunologist, and will likely continue anti-seizure and immunosuppressant medications until they are able to slowly taper off of them.

Roughly 12 percent of patients who recovered from an acute episode of AE had a relapse episode within the next two years, which is why careful management of the disease is vital.

Causes

The causes of most AE cases remain unknown. The following have been linked to AE:

A teratoma, which is a type of tumor that releases antibodies that can trigger AE.
Paraneoplastic syndromes, which occur when antibodies that the body produces in response to cancer mistakenly attack other parts of the nervous system.
Infections of the nervous system.

“Current research is examining a genetic predisposition and an environmental exposure” says Dr. Sorond.