OVERVIEW

What is autoimmune encephalitis?

As the name suggests, autoimmune encephalitis is first and foremost a type of encephalitis. Like other forms of encephalitis, it presents with brain-related symptoms such as cognitive dysfunction, psychiatric and behavioral abnormalities, and seizures. The underlying cause is primarily mediated by autoimmune mechanisms—in simple terms, the patient's immune cells attack their own brain, triggering encephalitis.

Autoimmune encephalitis accounts for 10%–20% of all encephalitis cases. Diagnosis typically involves testing for specific antibodies in the body. Treatment is prolonged, often requiring weeks or even months in intensive care. The disease responds well to immunotherapy, and some cases may show spontaneous remission. The mortality rate is less than 10%.

What are the types of autoimmune encephalitis, and what are their characteristics?

Based on different antibody subtypes, autoimmune encephalitis can be classified into the following types:

• Anti-NMDA receptor encephalitis: The most common type, accounting for 80% of all autoimmune encephalitis cases. No epidemiological assessment has been conducted yet, but reported cases predominantly affect young women and children.
• Anti-LGI1 receptor encephalitis: The second most common type, mainly occurring in elderly men, with an annual incidence of less than one per million.
• Anti-Caspr2 receptor encephalitis: Primarily affects elderly men.
• Anti-AMPA receptor encephalitis: Mostly occurs in middle-aged women.
• Anti-GABA-A receptor encephalitis: More common in children.
• Anti-GABA-B receptor encephalitis: Mainly affects adults.
• Others: Conditions such as anti-IgLON5 encephalopathy, anti-DPPX encephalitis, anti-GlyR encephalitis, anti-mGluR5 encephalitis, anti-mGluR1 encephalitis, anti-neurexin-3 alpha encephalitis, and anti-GFAP antibody encephalitis lack epidemiological studies.

SYMPTOMS

What are the symptoms of autoimmune encephalitis?

Patients with autoimmune encephalitis typically exhibit cognitive dysfunction, memory decline, abnormal mental behavior, epileptic seizures, language disorders, movement disorders (limb stiffness, hyperkinesia, chorea-like movements or unstable posture, etc.), involuntary movements, autonomic dysfunction (blood pressure fluctuations, tachycardia or bradycardia, etc.), varying degrees of impaired consciousness, or even coma. In general, patients often lose the ability to care for themselves during episodes.

• Anti-NMDA receptor encephalitis often presents with prodromal symptoms such as fever and headache, and female patients may have associated ovarian teratomas.
• Anti-LGI1 receptor encephalitis is also associated with hyponatremia.
• Anti-Caspr2 receptor encephalitis manifests with cerebellar symptoms and peripheral nerve hyperexcitability, among others.
• Most patients with anti-AMPA receptor encephalitis have underlying tumors.
• Anti-IgLON5 encephalitis primarily presents with sleep-related issues, such as snoring (obstructive sleep apnea syndrome), insomnia, hypersomnia, as well as gait abnormalities, dysphagia, and drooling.

CAUSES

What causes autoimmune encephalitis?

Currently, it is only known that the disease is related to autoimmunity, with excessive antibodies present in the body. Pathologically, immune cell infiltration (primarily lymphocytes) into the brain parenchyma can be observed, forming perivascular cuff-like changes. However, the deeper mechanisms remain unclear.

Is autoimmune encephalitis hereditary?

It is still unknown. Antibodies from anti-NMDA receptor encephalitis can be transmitted to the fetus through the placenta, but whether this leads to fetal death remains inconclusive.

Is autoimmune encephalitis contagious?

No.

DIAGNOSIS

How is autoimmune encephalitis diagnosed?

Generally, medical history and clinical manifestations of encephalitis can help doctors make a preliminary judgment, but a definitive diagnosis requires the detection of specific antibodies in the patient.

What tests are needed to diagnose autoimmune encephalitis?

• Lumbar puncture: A needle is inserted into the lower back to extract cerebrospinal fluid (CSF) for testing. This can determine the nature of the infection and also reduce intracranial pressure, alleviating symptoms like headaches and vomiting. This test is crucial for diagnosing intracranial infections but is invasive, requiring patient and family consent. The patient must remain still during the procedure, and family members may need to provide comfort. After the puncture, the patient must lie flat without a pillow for some time. The extracted CSF is tested for antibodies to identify autoimmune antibodies. For example, anti-NMDAR encephalitis can be confirmed by detecting IgG antibodies against the GluN1 (also called NR1) subunit of the NMDAR in serum or CSF.
• Blood test: Similar to CSF testing, blood is drawn to check for antibodies.
• Electroencephalogram (EEG): Electrodes are placed on the scalp to monitor brain waves. This is typically used to identify the type of brain wave activity during seizures. For instance, anti-NMDA receptor encephalitis may show a characteristic "extreme delta brush" pattern on EEG.
• Brain MRI: Helps rule out cerebrovascular diseases or metastatic conditions, identifies affected brain regions, and aids in classification (e.g., anti-GABA-A receptor encephalitis may show multifocal FLAIR and T2 signal abnormalities). This procedure takes longer and may require scheduling in advance.

What diseases is autoimmune encephalitis easily confused with? How to differentiate them?

Autoimmune encephalitis is often mistaken for viral encephalitis or metabolic encephalitis. Testing for specific antibodies can help distinguish them. However, conditions like herpes simplex virus encephalitis may later trigger autoimmune encephalitis, though the exact mechanism remains unclear.

TREATMENT

Which department should I visit for autoimmune encephalitis?

Neurology.

Is it necessary to seek medical treatment for autoimmune encephalitis?

Yes. This disease cannot heal on its own.

How should autoimmune encephalitis be treated specifically?

• For autoimmune encephalitis, immunotherapy should be prioritized, such as high-dose methylprednisolone therapy, intravenous immunoglobulin, or plasma exchange.
• For patients with concurrent tumors, tumor resection is recommended when appropriate.
• Symptomatic treatment is also required. For example, antiepileptic drugs should be administered to patients with seizures, and antipsychotic treatment should be given to those with significant psychiatric symptoms.

Can autoimmune encephalitis be cured?

Yes. However, a small number of patients may still suffer from sequelae or even death due to severe illness, delayed treatment, or complications like infections.

DIET & LIFESTYLE

What should patients with autoimmune encephalitis pay attention to in daily life?

Most patients with autoimmune encephalitis lose consciousness during the onset of the disease and require intensive care unit (ICU) treatment. Nursing care should focus on preventing pressure sores and infections, similar to other critically ill patients. After discharge, they can live like normal individuals without special precautions.

Does autoimmune encephalitis affect fertility?

No. However, pregnant women should monitor their antibody levels.

Can patients with autoimmune encephalitis fly, engage in strenuous exercise, or travel to high-altitude areas?

Yes, after the encephalitis is cured.

PREVENTION

Can autoimmune encephalitis be prevented? How to prevent it?

Current research is still unclear, so it cannot be prevented.