- WHAT IS ENCEPHALITIS?
Encephalitis is an inflammation of the brain. It is caused either by an infection invading the brain (infectious encephalitis) or through the immune system attacking the brain in error (post-infectious or autoimmune encephalitis).
Anyone at any age can get encephalitis. There are up to 6,000 cases in the UK each year and potentially hundreds of thousands worldwide. In the USA there were approximately 250,000 patients admitted to hospital with a diagnosis of encephalitis in the last decade.
- CAUSES OF ENCEPHALITIS?
The inflammation is caused either by an infection invading the brain (infectious encephalitis) or through the immune system attacking the brain in error (post-infectious or autoimmune encephalitis). Viruses are the most frequently identified cause of infectious encephalitis (e.g. herpes viruses, enteroviruses, West Nile, Japanese encephalitis, La Crosse, St. Louis, Western equine, Eastern equine viruses and tick-borne viruses). Any virus has the potential to produce encephalitis, but not everybody who is infected with these viruses will develop encephalitis. Very rarely, bacteria, fungus or parasites can also cause encephalitis.
Some types of autoimmune encephalitis such as acute disseminated encephalomyelitis (ADEM) are caused by infection in which case the term ‘post-infectious encephalitis’ is used. Other forms of autoimmune encephalitis are associated with finding specific antibodies in blood such as VGKC complex (anti-LGI1 and Caspr2), NMDA receptor, GAD, AMPAR and GABA antibodies. Antibodies, also called immunoglobulins, are large Y-shaped proteins which identify and help remove foreign antigens such as viruses and bacteria. The reason why these antibodies are produced by the immune system in people with autoimmune encephalitis is not known in most cases. Sometimes a tumour (benign or cancerous) may generate the antibody.
- SYMPTOMS OF ENCEPHALITIS
Infectious encephalitis usually begins with a ‘flu-like illness’ or headache. Typically more serious symptoms follow hours to days, or sometimes weeks later. The most serious finding is an alteration in the level of consciousness. This can range from mild confusion or drowsiness, to loss of consciousness and coma. Other symptoms include a high temperature, seizures (fits), aversion to bright lights, inability to speak or control movement, sensory changes, neck stiffness or uncharacteristic behaviour.
Autoimmune encephalitis often has a longer onset. Symptoms will vary depending on the type of encephalitis related antibody but may include: confusion, altered personality or behaviour, psychosis, movement disorders, seizures, hallucinations, memory loss, or sleep disturbances.
- DIAGNOSIS OF ENCEPHALITIS
Symptoms alone often do not allow sufficient ability to distinguish between the many diseases that can mimic encephalitis. Therefore, doctors perform a variety of hospital tests such as spinal tap (lumbar puncture), brain scans (computerised tomography -CT or magnetic resonance imaging - MRI), electroencephalogram (EEG) and various blood tests. Sometimes, some of the tests cannot be taken immediately because of the patient’s medical state (e.g. patient is agitated). Nevertheless, it is important that investigations are carried out as soon as possible as prompt diagnosis reduces mortality and improves the outcomes.
- TREATMENT FOR ENCEPHALITIS
Treatment of patients with encephalitis has two aims. Firstly, the patient will receive specific treatment for the cause of their encephalitis: antivirals for viral types of encephalitis (aciclovir for herpes simplex encephalitis); antibiotics for bacterial types and immunomodulatory drugs for autoimmune encephalitis (e.g. steroids, intravenous immunoglobulin, plasma exchange). For more information about the treatment in autoimmune encephalitis please download