In simple terms, Encephalitis means inflammation of Brain. It can be mainly because of either a direct infection of the Brain by some organism or virus or because of immune response to some provocation (infection or without infection also) outside the Brain.
It can be a short fulminant (in that case usually lethal) or a long drawn indolent course of the disease. Brain-related symptoms like Headache/ giddiness/ vomiting are the main and minimum characteristics. Fever may or may not be present and if present – may precede or coincide with the Brain-related symptoms. In a progressive disease the person goes into sleepiness and unconsciousness. Mortality (death) or morbidity (loss of function of body parts) largely depends on the characteristics of the primary infection.
Organisms responsible for encephalitis
Viruses are the most common cause – Mostly virus is not identified! Anyways there is very little specific treatment available against virus. Herpes is the commonest named virus, other viruses like arbovirus (St. Louis encephalitis, West Nile encephalitis virus), bunyavirus (La Crosse strain), arenavirus(lymphocytic choriomeningitis virus), reovirus (Colorado tick virus), and henipaviruses. The Powassan virus is a rare cause.
Acyclovir is one of the most useful medication with uncertain effectiveness.
Bacterial – small percentage of encephalitis may result due to bacterial meningitis progressing to encephalitis. rarely bacterial meningitis may be a direct cause by the bacteria. Toxoplasma, Malaria, primary amoebic encephalitis are other possible causes.
HIV related encephalitis or encephalitis in the HIV patients is important as in generally reduced immunity is the major predisposing factor for lethal encephalitis.
Transmission – is the important perspective. As there is no effective and specific treatment, a transmission which happens mostly through water, mosquito bites or animal contacts needs to be avoided and controlled.
Writer Intro- Dr Manish Kumar is a renowned Neurosurgeon in India as well as in Asia. Presently he is working with Park Hospital, India as a HOD neuro.