ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

What is Encephalitis?

Updated on April 28, 2011

Encephalitis is an inflammation of the brain occurring in man as well as in other animals. It is often accompanied by inflammation of the spinal cord (encephalomyelitis) or the meninges, the membranes covering the brain (meningoencephalitis). A wide variety of bacteria, spirochetes, fungi, and parasites may invade the central nervous system and cause an inflammation, but the term "encephalitis" is usually restricted to those inflammations caused by viral infections or allergic reactions that may follow viral infections.

The signs and symptoms of encephalitis vary according to the part of the brain or spinal cord involved. They include convulsions, confusion, stupor, or coma; speech difficulties, such as aphasia or mutism; muscular weakness on one side of the body; involuntary movements, muscular incoordination, and jerky motions; nystagmus (rapid involuntary movements of the eyeballs) and facial weakness. Signs of meningeal involvement include fever, headache, stiff neck, and an increase in the number of white blood cells in the spinal fluid.


Types of Encephalitis

A large number of viruses may invade the nervous system, but relatively few occur frequently enough to be of importance. The major group consists of the arthropod-borne viruses, which are transmitted by mosquitoes and other arthropods. These infections tend to occur during specific seasons and in certain geographic locations. Mosquito-borne infections, such as western equine encephalitis, St. Louis encephalitis, Japanese B. encephalitis, and eastern equine encephalitis, occur in late summer and early fall. They are acute, devastating diseases of the cerebrum and are often fatal. Those who survive are usually left with neurological damage. Tick-borne infections, such as Russian spring-summer encephalitis, are very similar to those borne by mosquitoes.

Acute inclusion cell encephalitis, which is caused by the herpes simplex virus (the cold sore virus), occurs throughout the world at all times of the year. It is fatal in about one third of all cases, and many patients who survive are left with seizures, impairment of mental function, and a type of psychosis in which memory is impaired. Subacute inclusion cell encephalitis, also called subacute sclerosing panencephalitis, chiefly affects children and is probably caused by the measles virus. It is characterized by chronic, progressive mental deterioration, muscular incoordination, and jerky movements. Rarer forms of encephalitis are caused by the viruses that cause rabies, mumps, and polio.

Acute disseminated encephalomyelitis is a disorder of the brain and spinal cord characterized by widespread inflammation and other changes in the nerve tissue around small veins. These changes may occur as complications of measles, chicken pox, or smallpox or rabies vaccinations. They are not caused by a direct invasion of the nerve tissue by the viruses but by an altered immune response on the part of the nervous system to the preceding viral invasion.

An epidemic of encephalitis called encephalitis lethargica followed World War I and was prevalent for about the next 10 years. The causative virus was never identified, and the disease seems to have disappeared, but the symptoms caused by this disease are still observed.


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)