Encephalitis

Victims are usually exposed to viruses resulting in encephalitis by insect bites or food and drink. The most frequently encountered agents are arboviruses (carried by mosquitoes or ticks) and enteroviruses (coxsackievirus, poliovirus and echovirus). Some of the less frequent agents are measles, rabies, mumps, varicella and herpes simplex viruses.

Patients with encephalitis suffer from fever, headache, vomiting, confusion, drowsiness and photophobia. The symptoms of encephalitis are caused by the brain's defense mechanisms activating to get rid of infection (brain swelling, small bleedings and cell death). Neurologic examination usually reveals a stiff neck due to the irritation of the meninges covering the brain. Examination of the cerebrospinal fluid obtained by a lumbar puncture procedure reveals increased amounts of proteins and white blood cells with normal glucose. A CT scan examination is performed to reveal possible complications of brain swelling, brain abscess or bleeding. Lumbar puncture procedure is performed only after the possibility of a prominent brain swelling is excluded by a CT scan examination.

Treatment is usually symptomatic. Reliably tested specific antiviral agents are available only for a few viral agents (e.g. aciclovir for herpes encephalitis) and are used with limited success.

Encephalitis lethargica is an atypical form of encephalitis which caused an epidemic from 1917 to 1928. There have only been a small number of isolated cases since, though in recent years a few patients have shown very similar symptoms. The cause is now thought to be a bacterial agent. As depicted in the book Awakenings by doctor Oliver Sacks, which was made into the film starring Robin Williams and Robert De Niro, the disease sometimes caused catatonia which could persist for decades.

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