HISTORY. Obtain a history of recent illnesses, which may include an upper respiratory infection or a minor systemic illness that caused headache, muscle ache, malaise, sore throat, and runny nose. Note if the patient has other sites of infection, such as a recent skull fracture or head injury, middle ear infection, or sinus infection. Ask if the patient has had a recent immunization, exposure to mumps or HSV, animal bites, recent travel, or exposure to epidemic outbreaks or mononucleosis. Ask if a child has been playing in a rural area where exposure to ticks or mosquitoes was possible.

316 Encephalitis

Encephalitis typically has an abrupt onset. The patient, parents, or family may describe altered respiratory patterns, fever, headache, nuchal (neck) rigidity, and vomiting. Neurological symptoms generally follow 24 to 48 hours after the initial onset; often, a seizure is the initial presenting symptom. The patient and family may describe other symptoms such as facial palsies, difficulty speaking, and decreased movement and sensation of the extremities.

PHYSICAL EXAMINATION. The patient appears acutely ill with an altered mental status that may range from mild confusion to delirium and coma. The patient may have tremors, cranial nerve palsies, and absent superficial or exaggerated deep tendon reflexes. There may be a decrease in sensation, along with weakness or even paralysis of the extremities. The patient may have no sense of taste or smell and may have difficulty speaking and swallowing. Heart and respiratory rates may be rapid. The patient's skin is often warm because of fever.

PSYCHOSOCIAL. Encephalitis can be life-threatening and lead to permanent disability; therefore, determine the patient's and family's ability to cope with sudden illness, anxiety, and stress, as well as disability. If the patient is a child, the parents may be excessively anxious. Analyze the family structure, the number of children, the financial resources, and the role of parental support systems to determine the extent of the problem.

Diagnostic Highlights


Normal Result

Abnormality with Condition


Lumbar puncture and cerebral spinal fluid (CSF) analysis

Pressure: 70-180 mm H2O Glucose: 45-80 mg/dL

Protein: 15-45 mg/mL

Slight to moderate increase in proteins and white blood cells in the CSF; normal glucose level. CSF pressure is often normal or slightly increased. If the patient has herpes simplex virus, the CSF may contain red blood cells

Encephalitis is usually caused by viral infections rather than bacterial, hence the normal CSF glucose

Polymerase chain reaction (PCR)

Negative for herpes simplex virus (HSV)

Positive for HSV

Produces relatively large numbers of copies of DNA from a source to determine if HSV is present in the sample; negative PCR does not completely rule out HSV encephalitis

Other Tests: Electroencephalogram (EEG), computed tomography (CT) scan, magnetic resonance imaging (MRI), cerebrospinal fluid (CSF) cultures, and radionuclide scans

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