Encephalitis

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Encephalitis is sudden inflammation (swelling) in the brain. It is usually caused by viruses, bacteria, or other pathogens. As the brain swells, it can get damaged when it gets crushed against the skull. Encephalitis can cause serious symptoms, like seizures and strokes, and can be fatal.[1] In 2013, encephalitis killed about 77,000 people in the world.[2]

Signs and symptoms[change | change source]

Usually, adults with encephalitis have a fever that starts suddenly, a headache, confusion, and sometimes seizures. Younger children or infants may be irritable (easily upset), not want to eat, and have a fever. Usually, patients are either very tired or confused.[3]

A stiff neck is a sign that the person has either meningitis (inflammation of the meninges, which cover the brain) or meningoencephalitis (swelling of both the meninges and the brain).[4]

Causes[change | change source]

Viruses[change | change source]

Viral encephalitis can happen when a virus infects the brain. The most common causes are the rabies virus, Human Papillomavirus (HPV), the polio virus, and the measles virus.[5] Viral encephalitis can also be caused by a latent virus - a virus that hides from the body's immune system the brain's nerve cells. Two examples of viruses that cause latent infection are the varicella-zoster viruses, which can hide in the brain after causing chicken pox, and the herpes simplex virus.[6]

About 100 different viruses can infect the brain.[7] Other examples include West Nile virus, Chikungunya virus, and Japanese encephalitis virus.[8]

Bacteria[change | change source]

Encephalitis can happen when a person gets a bacterial infection, like bacterial meningitis.[9] It can also be a complication of an infectious disease that a person already has, like syphilis. This is called "secondary encephalitis."[10]

Examples of other bacteria which can cause encephalitis are Staphylococcus aureus, which causes toxic shock syndrome; Bordetella pertussis, which causes pertussis (whooping cough); and types of Borellia bacteria, which cause Lyme disease.

Parasites[change | change source]

Some parasites can infect the brain, especially in people who have weak immune systems. Examples include Toxoplasma gondii, which causes toxoplasmosis; two parasites from the species Trypanosoma brucei, which cause African trypanosomiasis (African sleeping sickness); and Plasmodium parasites, which cause malaria.

Autoimmune diseases[change | change source]

Autoimmune diseases can cause encephalitis if the body's immune system attacks the brain, the spinal cord, and their nerves. Two examples are autoimmune encephalitis and acute disseminated encephalitis. [11][12]

Illustration showing what happens during a lumbar puncture

Diagnosis[change | change source]

Encephalitis can be diagnosed in a few different ways:[13]

  • An MRI (brain scan) can show brain swelling, and also show whether there are other brain problems causing a patient's symptoms
  • An EEG (a picture of the brain's electrical activity) will show signals that are not normal
  • A lumbar puncture (spinal tap) will show whether there is an infection in the cerebrospinal fluid (which bathes the brain and spinal cord)
  • Blood tests or urine tests may show whether a person has encephalitis, or if they have another illness instead

Treatment[change | change source]

Some treatments for encephalitis depend on the cause:[14]

Other treatments are "supportive" - they treat the symptoms of encephalitis. For example:[14][1]

A child gets a polio vaccine

Prevention[change | change source]

Vaccines have made encephalitis from some diseases much less common. These diseases include measles, mumps, rubella (German measles), polio, varicella (chicken pox), and pertussis (whooping cough).[14] There are also vaccines for rabies, bacterial meningitis, Japanese encephalitis, Human Papillomavirus (HPV), and some other diseases that can cause encephalitis.[15]

People can protect themselves from diseases that are spread by insects, like Lyme disease and malaria, by avoiding insect bites. For example, they can use bug spray; wear long sleeves and long pants; sleep under a mosquito net; and make sure they have good window and door screens.[16]


References[change | change source]

  1. 1.0 1.1 "Meningitis and Encephalitis Fact Sheet". www.ninds.nih.gov. : National Institute of Neurological Disorders and Stroke (NINDS). http://www.ninds.nih.gov/disorders/encephalitis_meningitis/detail_encephalitis_meningitis.htm. Retrieved February 3, 2016.
  2. Naghavi M; Wang H; et al. 2014. "Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990-2013: A systematic analysis for the Global Burden of Disease Study 2013". The Lancet 385 (9963): 117–71. doi:10.1016/S0140-6736(14)61682-2. PMC 4340604. PMID 25530442.
  3. "Symptoms of encephalitis". NHS Choices. National Health Service of the United Kingdom. December 16, 2014. http://www.nhs.uk/Conditions/Encephalitis/Pages/Symptoms.aspx. Retrieved February 3, 2016.
  4. Shmaefsky, Brian; Babcock, Hilary (January 1, 2010). Meningitis. Infobase Publishing. ISBN 9781438132167. https://books.google.com/books?id=KI5p3pADvSsC&pg=PA90&dq=meningoencephalitis+symptoms+stiff+neck&hl=en&sa=X&ved=0CCsQ6AEwAGoVChMIk7_kzqCSxwIVQYsNCh2nzwvd#v=onepage&q=meningoencephalitis%2520symptoms%2520stiff%2520neck&f=false.
  5. Fisher DL; Defres S; et al. 2015. "Measles-induced encephalitis". QJM 108 (3): 177–182. doi:10.1093/qjmed/hcu113. PMID 24865261.
  6. Rozenberg F; Deback C; et al. 2011. "Herpes simplex encephalitis: From virus to therapy". Infectious Disorders Drug Targets 11 (3): 235–250. doi:10.2174/187152611795768088. PMID 21488834.
  7. van den Pol, AN 2009. "Viral infection leading to brain dysfunction: More prevalent than appreciated?". Neuron (Elsevier) 64 (1): 17-20. doi:10.1016/j.neuron.2009.09.023. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2782954/. Retrieved February 2, 2016.
  8. Kennedy PGE 2004. "Viral Encephalitis: Causes, Differential Diagnosis, and Management". Journal of Neurology, Neurosurgery & Psychiatry 75 (suppl 1): i10-i15. doi:10.1136/jnnp.2003.034280. ISSN 1468-330X. PMC 1765650. PMID 14978145. http://jnnp.bmj.com/content/75/suppl_1/i10.
  9. Ashar, Bimal H.; Miller, Redonda G.; Sisson, Stephen D. (January 1, 2012). Johns Hopkins Internal Medicine Board Review: Certification and Recertification. Elsevier Health Sciences. ISBN 1455706922. https://books.google.com/books?id=KLBZ85zbTeYC&pg=PA113&dq=bacterial+meningitis+inflmation+of+encepha+definition&hl=en&sa=X&ved=0CGAQ6AEwCGoVChMI8PLmjZqSxwIVS6KACh03_QJ_#v=onepage&q=bacterial%2520meningitis%2520inflmation%2520of%2520encepha%2520definition&f=false.
  10. Hama K; Ishiguchi H; et al. 2008. "Neurosyphilis with Mesiotemporal Magnetic Resonance Imaging Abnormalities". Internal Medicine 47 (20): 1813–1817. doi:10.2169/internalmedicine.47.0983. https://www.jstage.jst.go.jp/article/internalmedicine/47/20/47_20_1813/_article.
  11. Howes, David S. (October 12, 2015). "Encephalitis: Practice Essentials, Background, Pathophysiology". Medscape. WebMD LLC. http://emedicine.medscape.com/article/791896-overview#a4. Retrieved February 3, 2016.
  12. Armangue T; Petit-Pedro M; et al. 2012. "Autoimmune Encephalitis in Children". Journal of Child Neurology 27 (11): 1460–1469. doi:10.1177/0883073812448838. ISSN 0883-0738. PMC 3705178. PMID 22935553. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705178/.
  13. "Encephalitis - Diagnosis". NHS Choices. National Health System of the United Kingdom. December 16, 2014. http://www.nhs.uk/Conditions/Encephalitis/Pages/Diagnosis.aspx. Retrieved February 3, 2016.
  14. 14.0 14.1 14.2 Kaneshiro, Neil (August 30, 2014). "Encephalitis". MedlinePlus Medical Encyclopedia. United States National Library of Medicine. http://www.nlm.nih.gov/medlineplus/ency/article/001415.htm. Retrieved February 3, 2015.
  15. "Vaccines and Preventable Diseases". CDC.gov. United States Centers for Disease Control and Prevention. September 3, 2015. http://www.cdc.gov/vaccines/vpd-vac/default.htm. Retrieved February 2, 2016.
  16. "West Nile Virus: Prevention & Control". CDC.gov. United States Centers for Disease Control and Prevention. November 10, 2015. http://www.cdc.gov/westnile/prevention/index.html. Retrieved February 1, 2016.