Viral encephalitis laboratory findings

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Template:Encephalitis Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, MBBS [2]

Overview

Encephalitis is an acute inflammation of the brain, commonly caused by a viral infection. Sometimes, encephalitis can result from a bacterial infection, such as bacterial meningitis, or it may be a complication of other infectious diseases like rabies (viral) or syphilis (bacterial). Certain parasitic or protozoal infestations, such as toxoplasmosis, malaria, or primary amoebic meningoencephalitis, can also cause encephalitis in people with compromised immune systems. Brain damage occurs as the inflamed brain pushes against the skull, and can lead to death.

Lab tests

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.

Lab tests

  • Complete blood count with differential
  • Coagulation profile
  • Serum electrolyte {helps to rule out syndrome of inappropriate secretion of antidiuretic hormone (SIADH)}
  • Urine electrolyte {helps to rule out syndrome of inappropriate secretion of antidiuretic hormone (SIADH)}
  • Serum glucose (helps to rule out confusion due to hypoglycemia, diabetic ketoacidosis and comparing serum glucose with CSF glucose)
  • Blood urea nitrogen and serum creatinine levels (to rule out confusion due to dehydration)
  • Liver function test (to rule out hepatic involvement
  • Lumbar puncture and CSF examination
  • Culture of cerebrospinal fluid (CSF), blood, or urine (however, this test is rarely useful)
  • Tests that detect antibodies to a virus (serology tests)
  • Test that detects tiny amounts of virus DNA (polymerase chain reaction -- PCR)

See also

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