Closing in on clues to encephalitis

Nursing, Apr 2003 by Wisniewski, Amy

COMBATING INFECTION

CHARACTERIZED BY swelling of brain tissue and surrounding meninges, encephalitis is usually triggered by a viral infection (see Identifying Common Viral Culprits). Less-- common causes include bacterial, fungal, and parasitic infections; cancer; and exposure to toxins or drugs.

The severity of encephalitis depends on the underlying cause, the patient's age and condition, and the duration of illness before treatment. People who are immunocompromised are especially vulnerable.

Primary encephalitis indicates that a pathogen or toxin has directly attacked the brain and spinal cord. Herpes simplex and mosquito-borne viruses are most likely to trigger primary encephalitis. Secondary encephalitis is caused by an infection in another part of the body or by the body's immune response to a foreign substance or toxin. Usually self-limiting, this type tends to be milder than primary encephalitis.

Identifying signs and symptoms

Depending on the type of encephalitis and its severity, signs and symptoms may develop hours to weeks after exposure. Most people with viral encephalitis experience mild symptoms (fever and headache), or no symptoms at all, and recover quickly. Bacterial encephalitis usually causes more severe illness.

Confusion and disorientation are the most common symptoms of encephalitis in adults. Other possible signs and symptoms include headache, photophobia, high fever, lethargy, seizures, hallucinations, aphasia, nuchal rigidity, and coma. Tremor and Parkinsonian-like rigidity are associated with tick-borne viral encephalitis.

Because many of these symptoms are easily confused with stroke or other neurologic disorders, a thorough health history can uncover important diagnostic clues. When taking the patient's history, identify illnesses, animal and insect bites, recent travel, medications, immunocompromised state, and exposure to toxic substances. Examine his skin for bites or rashes.

If the health care provider suspects encephalitis, she'll order magnetic resonance imaging or computed tomography of the head to look for edema, focal lesions, and midline shifts. Other diagnostic tests include an electroencephalogram, cerebrospinal fluid analysis, and blood work. A brain biopsy may be needed for a definitive diagnosis. Until she rules out a bacterial cause, she may order a broad-spectrum antibiotic.

Treatment options

Once the health care provider determines the cause of encephalitis, she'll select a treatment plan. Viral encephalitis caused by herpes simplex is treated with an antiviral medication. Bacterial encephalitis is treated with a narrow-spectrum antibiotic that targets the offending bacteria. Depending on the patient's condition, you may also give anticonvulsants, antipyretics, anti-- inflammatory medications, and analgesics. If you're giving opioids for pain control, carefully monitor the patient's sedation level.

Regardless of the underlying cause of encephalitis, you'll provide supportive treatment, including fluids and nutrition. Initiate seizure precautions and interventions to reduce intracranial pressure. Because syndrome of inappropriate antidiuretic hormone is common, monitor fluid and electrolyte balance closely. Many patients with encephalitis

recover fully, but some experience lingering or permanent problems, such as motor or cognitive deficits, seizure disorders, memory loss, hearing or vision loss, and paralysis. Physical therapy and ongoing support from the health care team can help your patient recover as fully as possible.

BY AMY WISNIEWSKI, RN, BSN

Amy Wisniewski is a case manager for Lehigh Valley Hospital, in Allentown, Pa.