Viral encephalitis

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Viral encephalitis
ICD-10	A83-A86, B94.1, G05
ICD-9	323
DiseasesDB	22543
MeSH	D004660

Template:Encephalitis Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Risk Factors

Encephalitis may be caused by a variety of afflictions. One such affliction is rabies.

Diagnosis

Adult patients with encephalitis present with acute onset of fever, headache, confusion, and sometimes seizures. Younger children or infants may present with irritability, anorexia and fever.

Lab Tests

Neurological examinations usually reveal a drowsy or confused patient. Stiff neck, due to the irritation of the meninges covering the brain, indicates that the patient has either meningitis or meningeoncephalitis. Examination of the cerebrospinal fluid obtained by a lumbar puncture procedure usually reveals increased amounts of protein and white blood cells with normal glucose, though in a significant percentage of patients, the cerebrospinal fluid may be normal. CT scan often is not helpful, as cerebral abscess is uncommon. Cerebral abscess is more common in patients with meningitis than encephalitis. Bleeding is also uncommon except in patients with herpes simplex type 1 encephalitis. Magnetic resonance imaging offers better resolution. In patients with herpes simplex encephalitis, electroencephalograph may show sharp waves in one or both of the temporal lobes. Lumbar puncture procedure is performed only after the possibility of prominent brain swelling is excluded by a CT scan examination. Diagnosis is often made with detection of antibodies against specific viral agent (such as herpes simplex virus) or by polymerase chain reaction that amplifies the RNA or DNA of the virus responsible.

Pathophysiology

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Medical Therapy

Treatment is usually symptomatic. Reliably tested specific antiviral agents are available only for a few viral agents (e.g. acyclovir for herpes simplex virus) and are used with limited success for most infection except herpes simplex encephalitis. In patients who are very sick, supportive treatment, such as mechanical ventilation, is equally important.

Encephalitis lethargica

Main article: Encephalitis lethargica

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 either a bacterial agent or an autoimmune response following infection.

Limbic system encephalitis

In a small number of cases, called limbic encephalitis, the pathogens responsible for encephalitis attack primarily the limbic system (a collection of structures at the base of the brain responsible for basic autonomic functions).

See also

• Granulomatous amoebic encephalitis
• Japanese Encephalitis
• St. Louis Encephalitis
• Equine Encephalitis
• Rasmussen's encephalitis
• La Crosse encephalitis
• Murray Valley encephalitis virus
• California encephalitis virus
• meningoencephalitis
• Tick-borne meningoencephalitis
• Herpes simplex