Encephalitis
What is Encephalitis ?
Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. It can be caused by viral or bacterial infections, or by immune cells mistakenly attacking the brain. Viruses that can lead to encephalitis can be spread by insects such as mosquitos and ticks.
When inflammation is caused by an infection in the brain, it’s known as infectious encephalitis. And when it’s caused by the immune system attacking the brain, it’s known as autoimmune encephalitis. Sometimes there is no known cause. Encephalitis can sometimes lead to death. Getting diagnosed and treated right away is important because it’s hard to predict how encephalitis may affect each person.
Symptoms
- Headache
- Fever
- Aches in muscles or joints
- Fatigue or weakness
- Stiff neck
- Confusion, agitation or hallucinations
- Seizures
- Irregular movements
- Muscle weakness
- Trouble with speech or hearing
- Loss of consciousness, including coma
- Nausea and vomiting
Cause
In about half of the patients, the exact cause of encephalitis is not known. In those for whom a cause is found, there are two main types of encephalitis. Infectious encephalitis. This condition usually occurs when a virus infects the brain. The infection may affect one area or be widespread. Viruses are the most common causes of infectious encephalitis, including some that can be passed by mosquitoes or ticks. Very rarely, encephalitis may be caused by bacteria, fungi, or parasites. Autoimmune encephalitis. This condition occurs when your immune cells mistakenly attack the brain or make antibodies targeting proteins and receptors in the brain. The exact reason why this happens is not completely understood. Sometimes, autoimmune encephalitis can be triggered by cancerous or noncancerous tumors, known as paraneoplastic syndromes of the nervous system. Other types of autoimmune encephalitis, such as acute disseminated encephalomyelitis (ADEM), can be triggered by an infection in the body. This is known as post-infectious autoimmune encephalitis. In many instances, no trigger for the immune response is found.
Risk Factors
Anyone can develop encephalitis. Factors that may increase the risk include, Age. Some types of encephalitis are more common or more serious in certain age groups. In general, young children and older adults are at greater risk of most types of viral encephalitis. Similarly, some forms of autoimmune encephalitis are more common in children and young adults, whereas others are more common in older adults. Weakened immune system. People who have HIV/AIDS, take immune-suppressing medicines or have another condition causing a weakened immune system are at increased risk of encephalitis. Geographical regions. Mosquito- or tick-borne viruses are common in particular geographical regions. Season of the year. Mosquito- and tick-borne diseases tend to be more common in summer in many areas of the United States. Autoimmune disease. People who already have an autoimmune condition may be more prone to develop autoimmune encephalitis. Smoking. Smoking increases the chances of developing lung cancer, which in turn increases the risk of developing paraneoplastic syndromes including encephalitis.
When to see a Doctor
Get medical care right away if you experience any of the more-serious symptoms associated with encephalitis. A bad headache, fever and change in consciousness require urgent care. Infants and young children with any symptoms of encephalitis also need urgent care.