Encephalitis Overview
Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. It can be caused by several factors, including viral infection, autoimmune inflammation, bacterial infection, insect bites, and others. When caused by an infection in the brain, it's known as infectious encephalitis, and when caused by the immune system attacking the brain, it's known as autoimmune encephalitis. In some cases, the cause of encephalitis is unknown.
Symptoms:
Encephalitis may lead to various symptoms, including confusion, personality changes, seizures, problems with movement, changes in sight, or hearing.
Most people with infectious encephalitis experience flu-like symptoms initially, such as headache, fever, muscle or joint aches, fatigue, or weakness. These symptoms are usually followed by more severe symptoms over time, such as stiff neck, confusion, agitation, hallucinations, seizures, muscle weakness, problems with speech or hearing, and even loss of consciousness or coma. In infants and young children, additional signs may include bulging in the soft spots of the skull, nausea, vomiting, stiffness affecting the whole body, poor feeding, and irritability.
For autoimmune encephalitis, symptoms may develop more slowly over several weeks, with changes in personality, memory loss, psychosis, hallucinations, seizures, vision changes, sleep problems, muscle weakness, problems with walking, abnormal movements, bladder and bowel problems, among others.
When to see a doctor:
Seek immediate medical care if you experience any severe symptoms associated with encephalitis, such as a severe headache, fever, or changes in consciousness.
Infants and young children with signs or symptoms of encephalitis should receive urgent care.
Causes:
In about half of patients, the exact cause of encephalitis remains unknown. For those in whom a cause is identified, there are two main types: infectious encephalitis and autoimmune encephalitis.
Infectious encephalitis occurs when a virus or other agent directly infects the brain. Viruses are the most common causes, including herpes simplex virus (HSV), Epstein-Barr virus, varicella-zoster virus, enteroviruses, mosquito-borne viruses (e.g., West Nile, La Crosse), tick-borne viruses (e.g., Powassan), and rabies virus (rarely).
Autoimmune encephalitis occurs when the immune system mistakenly attacks the brain or produces antibodies targeting brain proteins and receptors. The reason for this abnormal immune response is not entirely understood. Sometimes, it can be triggered by tumors (paraneoplastic and autoimmune encephalitis) or infections (post-infectious autoimmune encephalitis), while in many cases, no definitive trigger is identified.
Risk factors:
Encephalitis can affect anyone, but certain factors may increase the risk, such as age (young children and older adults are at greater risk), a weakened immune system (e.g., HIV/AIDS, immune-suppressing medicines), geographical regions (where mosquito- or tick-borne viruses are prevalent), season of the year (more common in summer), presence of autoimmune disease, and smoking (increases the risk of paraneoplastic autoimmune encephalitis due to lung cancer).
Complications:
The complications of encephalitis vary depending on factors like age, cause of infection, severity of the initial illness, and time from disease onset to treatment. Severe cases may result in coma or death due to brain inflammation and injury. Other complications can last for months or be permanent and may include persistent fatigue, muscle coordination problems, personality changes, memory problems, hearing or vision defects, and speech impairments.
Prevention:
The best way to prevent viral encephalitis is to avoid exposure to viruses that can cause the disease. Practicing good hygiene, not sharing utensils, teaching children good habits, and staying up to date with vaccinations are essential preventive measures.
To minimize exposure to mosquitoes and ticks, dressing to protect yourself, applying mosquito repellent, using insecticide, avoiding mosquito-prone areas, and getting rid of standing water sources outside your home are recommended. Additional protection for young children includes using mosquito netting for infants and using repellents with 10% to 30% DEET for older infants and children.