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Johns Hopkins Symptoms and Remedies

Johns Hopkins Medicine

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Encephalitis

What is it?

Encephalitis, a rare disorder, is inflammation of the brain, almost always due to a viral infection. In most cases a virus attacks the brain directly after it is contracted from the bite of an infected mosquito or, less often, a tick. Encephalitis may occur as an isolated case or in epidemics. Most cases occur during the summer and early fall, although infection is possible year-round in warm regions. Depending on the specific virus involved, the onset of symptoms may be sudden or may take over a week to develop. In some cases a flu-like illness with symptoms of fever, head- ache, muscle aches, and fatigue may be present for several days before more severe symptoms of vomiting, stiff neck, confusion, extreme drowsiness, or seizures develop; in other cases severe symptoms may appear immediately. In addition, symptoms may vary among different age groups. In infants, a swelling in the soft spot of the skull (fontanel) and a stiff neck may be pronounced; children may complain of a headache and exhibit a sensitivity to light; in adults, neurological disturbances—both physical and mental—may be prominent. Although most cases of encephalitis are mild and may be mistaken for a cold or flu, in some cases (especially among the very young and very old) encephalitis is life-threatening. The outlook is good for those who survive the first two weeks of the infection; however, neurological symptoms may take many months to subside fully. Severe attacks bear the risk of permanent brain damage or epilepsy. Chemotherapy is available only for infections with the herpes simplex virus. In other cases treatment is aimed at relieving the severity and duration of symptoms.

What Causes It?

  • Viral infection causes encephalitis. Most commonly, mosquitoes or ticks acquire an arbovirus from infected domestic animals (especially horses) or wild or domestic birds (such as crows) and may then transfer the virus to humans.
  • Occasionally, infections with herpes simplex virus may spread to the brain.
  • Human immunodeficiency virus (HIV) infection, mumps, measles, chicken pox, and infectious mononucleosis may rarely cause encephalitis.
  • Rarely, an adverse reaction to a vaccine may lead to encephalitis.

Prevention

  • Prevent insect bites by using insect repellent containing DEET (diethyltoluamide) during outdoor summer activities. Apply repellent to clothing; use sparingly on skin.
  • Cover exposed skin when in grassy, wooded, or swampy areas where mosquitoes and ticks may be present. Tuck long pants into socks, wear shoes instead of sandals, and wear long-sleeved shirts. Light-colored clothing makes ticks more visible.
  • During a more widespread encephalitis outbreak, limit outdoor exposure during times of greatest mosquito activity: early morning, late afternoon, and early evening.
  • Use fine-tipped, curved tweezers to remove a tick attached to your skin (see Lyme Disease for more information about tick removal). Do not use petroleum jelly, kerosene, or a lit cigarette to remove a tick; these removal methods are ineffective and may increase the likelihood of infection.
  • If possible, avoid areas where there is an outbreak of encephalitis.

Diagnosis

  • Lumbar puncture (spinal tap).
  • Blood tests.
  • Electroencephalogram (EEG).
  • CT (computed tomography) scans or MRI (magnetic resonance imaging).
  • In severe cases a brain biopsy may be required to determine the underlying cause and thus guide further treatment. Under general anesthetic, a tiny hole is drilled in the skull, and a needle is used to extract a sample of the affected brain tissue.

How to Treat It

  • The antiviral drug acyclovir may be administered intravenously to treat encephalitis due to the herpes simplex type 1 or type 2 viruses.
  • Corticosteroid drugs, such as dexamethasone, may be administered to reduce any inflammation of the brain.
  • Anticonvulsant drugs, such as phenytoin, may be given to prevent seizures.
  • Sedatives may be recommended to calm the patient.
  • Pain relievers like aspirin, acetaminophen, ibuprofen, or naproxen may be administered to reduce pain and fever. Aspirin should not be given to children with viral infections, owing to the risk of side effects (see Reye's Syndrome for more information).
  • Fluids and electrolytes (such as sodium and potassium) may be administered intravenously to prevent dehydration during treatment, and liquid nutrients may be given through a tube placed in the stomach via the nose.
  • A mechanical respirator may be required to aid breathing.
  • Antibiotics may be administered to treat an associated bacterial infection.
  • Speech, physical, and occupational therapy may be necessary during recovery in cases where a patient has suffered lasting brain damage.

When to Call a Doctor

  • Call a doctor immediately if you or your child develops nausea, severe headache, and a stiff neck, with or without a preceding flu-like illness or fever.
  • EMERGENCY Call an ambulance immediately if someone loses consciousness.