Autoimmune Encephalitis

Autoimmune encephalitis (AE) is a group of conditions that causes inflammation in the brain. This occurs when the immune system mistakenly attacks healthy brain cells. Symptoms can vary but often include memory loss, changes in thinking, changes in behavior, and seizures.

Autoimmune encephalitis differs from infectious encephalitis, which is caused by viruses or bacteria and requires different treatments. Research suggests the prevalence of autoimmune encephalitis is similar to that of infectious encephalitis.

The exact cause of AE is unknown. In some cases, it may be triggered by cancers, infections, or certain medications. People with an autoimmune disease or a family history of autoimmune disease may be at higher risk. Without treatment, AE can lead to serious complications, including death. However, many people recover fully with treatment, though some may have lasting symptoms.

Symptoms

Symptoms of autoimmune encephalitis can vary but often follow a pattern depending on the type of AE. Common signs include:

• Headache, fever, and other early infection-like symptoms

• Psychiatric symptoms such as anxiety, panic attacks, agitation, hallucinations, delusions, and trouble organizing thoughts

• Memory problems

• Language difficulties, including reduced speech or repetition of words and phrases

• Involuntary movements

• Seizures, which can be severe and require emergency care (status epilepticus)

• Changes in consciousness

• Sleep disturbances, including less sleep initially followed by excess sleep during recovery

The disease course can be progressive, with worsening symptoms over time, or relapsing-remitting, with alternating periods of improvement and decline.

Causes

Autoimmune encephalitis occurs when the immune system produces antibodies that mistakenly attack receptors in the brain, causing inflammation. Possible triggers include:

• Certain cancers, known as paraneoplastic AE

• Infections, such as herpes simplex virus

• Medications, including monoclonal antibodies or immunosuppressants after transplants

People with an autoimmune disease or a strong family history of autoimmune disease are more likely to develop AE.

Types of AE include:

• Anti-NMDA-receptor encephalitis, common in young women and children, causing seizures, facial movements, and psychosis

• Anti-GABA-B receptor encephalitis, often linked to small-cell lung cancer, causing seizures, confusion, and memory loss

• Anti-GABA-A receptor encephalitis, affecting adults and sometimes children, causing seizures, movement disorders, and behavioral changes

• Anti-AMPA receptor encephalitis, usually in women, causing confusion and memory loss

• Anti-LGI1 limbic encephalitis, more common in men, causing memory loss, confusion, and seizures

• Anti-CASPR2 associated encephalitis, affecting men, causing confusion, memory loss, sleep disturbances, nerve pain, and sometimes Morvan syndrome

• Anti-IgLON5 disease, causing abnormal sleep behaviors and movements after falling asleep

Risk factors

Risk factors for AE include:

• Previous occurrence of AE, especially if untreated

• Prior herpes simplex virus encephalitis

• Use of monoclonal antibodies or immunosuppressive medications after transplants

• Presence of tumors, particularly small-cell lung cancer

• Possible genetic predisposition being studied

Complications

Severe autoimmune encephalitis can cause:

• Status epilepticus, prolonged or repeated seizures with unconsciousness

• Respiratory failure requiring mechanical ventilation

• Autonomic dysfunction affecting heart rate, blood pressure, digestion, and urination

• High fevers

• Relapse of the condition, especially in anti-LGI1 or anti-CASPR2 associated AE

Prevention

Autoimmune encephalitis cannot always be prevented. Early cancer detection and treatment may reduce the risk of AE triggered by tumors. Discuss cancer risk and recommended screenings with a healthcare professional to help prevent related cases of AE.