Autoimmune Encephalitis (AE)

Autoimmune encephalitis (AE) is a type of brain inflammation caused by the immune system attacking healthy brain cells. Unlike infectious encephalitis, which is triggered by viruses or bacteria, autoimmune encephalitis happens when the body’s defense system mistakenly targets the brain. This can lead to a range of symptoms, from memory loss to changes in behavior.

AE can present in several different ways and may mimic other diseases. Some of the most common forms can present like:

• Rapid unexplained psychiatric decline
• Rapid and severe onset of dementia or Parkinson-like symptoms
• Unexplained and severe refractory seizures

Symptoms often begin suddenly and generally worsen over days to weeks. Early signs may include confusion, memory problems or changes in mood and behavior. Some people notice anxiety, depression, hallucinations or unusual thoughts. Seizures may develop. Limbic encephalitis often causes memory loss and personality change. Movement problems and sleep issues are common.

Symptoms may include:

• Memory loss or confusion
• Sudden changes in mood or personality
• Hallucinations or unusual thoughts
• Seizures
• Trouble moving or walking
• Difficulty speaking or finding words
• Severe body stiffness or rigidity

Keep a simple symptom log (date, what happened, how long it lasted, any triggers or new medicines) and bring it to your visit. This can help your care team see patterns quickly.

Call 911 or go to the nearest emergency department if someone has a seizure lasting more than 5 minutes, repeated seizures without recovery, severe trouble breathing, very high fever or rapidly worsening confusion.

Autoimmune encephalitis happens when antibodies from the immune system target proteins in the brain, causing inflammation. Examples include anti‑NMDA receptor, LGI1 and GAD-65 antibodies. Sometimes a tumor (for example, an ovarian teratoma) or a prior infection can trigger the immune system. Autoimmune encephalitis is not spread from person to person. Most people do not have a family history.

When to seek care

Get prompt medical attention if you notice new confusion, sudden behavior changes, new seizures or rapid mood shifts without a clear cause. These symptoms can be mistaken for mental health issues but may be autoimmune encephalitis.

How it’s diagnosed

Your team looks for autoimmune encephalitis and rules out other causes. Tests may include:

• Neurologic exam: checks memory, thinking, movement and reflexes
• MRI of the brain: looks for inflammation
• Lumbar puncture (spinal tap): checks spinal fluid for inflammation and AE‑related antibodies
• PET scan: evaluates brain metabolism
• EEG: looks for seizures or unusual brain activity
• Blood tests: may also check for autoimmune encephalitis‑related antibodies
• Cancer screening: when a subtype suggests higher risk

Treatment calms the immune system and reduces inflammation. At UC Health and UC Garner Neuroscience Institute, plans are tailored to each patient.

Common treatments include:

• Corticosteroids (reduce inflammation)
• Intravenous immunoglobulin (IVIG)
• Therapeutic plasma exchange (PLEX) to remove harmful antibodies
• If needed: medicines such as rituximab or cyclophosphamide
• Seizure medicines and support for symptoms
• If a tumor is found, treatment is a part of the care

Recovery and living with autoimmune encephalitis

Recovery is often gradual. Many people improve over months, and gains can continue for a year or longer. Some have ongoing challenges with attention, memory or mood.

Care that can help:

• Cognitive rehabilitation to support memory and attention
• Speech and occupational therapy for communication and daily activities
• Physical therapy for balance, coordination and strength
• Mental health care for anxiety, depression and sleep issues
• Regular follow‑up to watch for relapse and adjust treatment

Paraneoplastic neurological syndrome (PNS)

Paraneoplastic neurological syndromes are often misdiagnosed because they mimic other brain or nerve conditions. But spotting the link between new, unexplained neurological problems and cancer can lead to earlier detection and better outcomes.

PNS usually signals the presence of an underlying cancer—most often small cell lung cancer, breast cancer, ovarian cancer or lymphoma. Timely treatment of the cancer and the immune reaction can slow or stop the neurological damage.

Most Common Associated Cancers

• Small cell lung cancer: the most frequent trigger of PNS
• Breast cancer
• Ovarian cancer
• Testicular cancer
• Lymphoma or thymoma

Not everyone with these cancers develops PNS. It occurs in fewer than 1 out of 100 cancer patients, but when it does, the symptoms can develop quickly and be severe.

Treatment options

Treating paraneoplastic neurological syndrome focuses on two goals:

1. Stopping the immune attack on the nervous system.
2. Treating the underlying cancer. The sooner treatment begins, the better the chance of preventing permanent nerve damage.

At the UC Gardner Neuroscience Institute, you’ll find expertise in autoimmune encephalitis and related disorders, fast access to MRI, EEG, lumbar puncture and advanced antibody testing, and coordinated care across neurology, epilepsy, rehabilitation and behavioral health. Our team also includes a dedicated psychiatrist with specific training and expertise in autoimmune encephalitis.

Clinical trials may be available for eligible patients.

If you or a loved one needs answers, ask your doctor for a referral or contact our team to schedule an evaluation by calling 513-475-8730.