DRG Category: 98
Mean LOS: 7.1 days
Description: Medical: Non-Bacterial Infections of Nervous System Except Viral Meningitis With Complication or Comorbidity
Encephalitis, or inflammation of the brain, usually occurs when the cerebral hemispheres, brainstem, or cerebellum is infected by a microorganism. Approximately 2,000 cases of encephalitis are reported each year in the United States, but this is probably only a fraction of the cases. Most forms have mortality rates of less than 10%, with the exception of eastern equine encephalitis (EEE), for which mortality is as high as 50%. Determining the true incidence is impossible because reporting policies are neither standardized nor rigorously enforced.
When the virus invades the brain, it enters neural cells, which leads to interrupted function of the cells, congestion, hemorrhage, and an inflammatory response. When the brain becomes inflamed, lymphocytes infiltrate brain tissue and the meninges of the brain. Cerebral edema results, and ultimately, brain cells can degenerate, leading to widespread nerve cell destruction.
Encephalitis has two forms: primary and postinfectious (or para-infectious). The primary form of the disease occurs when a virus invades and replicates within the brain. Postinfectious encephalitis describes brain inflammation that develops in combination with other viral illnesses or following the administration of vaccines such as measles, mumps, and rubella. In that case, encephalitis occurs because of a hypersensitivity reaction that leads to demyelination of nerves. Complications from encephalitis can be short term or lifelong. Bronchial pneumonia and respiratory tract infections may complicate the course of encephalitis. Patients may go into a coma and experience all the complications of immobility, such as contractures and pressure ulcers. Other complications include epilepsy, parkinsonism, behavioral and personality changes, syndrome of inappropriate antidiuretic hormone secretion, and mental retardation. A comatose state may last for days, weeks, or months after the acute infectious state.
Most cases of encephalitis are related to viruses, and the most common cause is herpes simplex virus-1 (HSV-1) in adults. HSV-2 is more common in neonates and may be transmitted from a mother infected with genital herpes during childbirth. Herpes encephalitis has a range of clinical presentations and can be transmitted during birth, through the blood, or by neuronal transmission. Neuronal transmission often occurs from the peripheral neuron in retrograde fashion to the brain. Arboviruses are also common causes of encephalitis; although most people bitten by arbovirus-infected insects do not develop the disease, approximately 10% have overt symptoms. Transmission of arboviruses requires an insect vector and usually occurs in the Northern Hemisphere between June and October. The two most common arboviruses cause La Crosse encephalitis and St. Louis encephalitis. In the United States, most cases of nonepidemic encephalitis are caused by the La Crosse virus, are most common in rural areas of the Midwest, and affect children. Epidemics of both St. Louis encephalitis (found mostly in the East and Midwest) and western equine encephalitis (WEE; found across North America) have contributed a large number of the total cases since 1955. Many sources cite the St. Louis encephalitis virus as the most common form in this country, although many forms of the disease exist.
Although relatively uncommon, the deadliest arbovirus is EEE, which is mostly encountered in the New England region. Other viruses include WEE (most common in rural communities west of the Mississippi River), Powassan (POW) virus, the only arbovirus known to be transmitted by ticks, Epstein-Barr virus, and cytomegalovirus. Encephalitis has also been associated with many other diseases, including Creutzfeldt-Jakob disease, HSV (specifically HSV-1), kuru, malaria, mononucleosis, rabies, trichinosis, and typhus.
Heritable immune responses could be protective or increase susceptibility. Susceptibility to herpes simplex encephalitis is linked to mutations in TLR3 and UNC93B1.
Encephalitis may occur at any age. However, people at the extremes of age (the very old and the very young) are most at risk as are people with weak immune systems. Encephalitis caused by HSV-1 is most common in children and young adults. La Crosse encephalitis is most common in children from age 5 to 10 years. EEE commonly occurs in children younger than age 10 years and in older adults, whereas WEE occurs in infants under a year old and in older adults. St. Louis encephalitis is seen most often in adults older than age 35 years.
Ethnicity and race have no known effect on the risk for encephalitis. People who have infections with HIV are immunosuppressed and are more at risk for encephalitis than people with normal immune systems.
The Japanese virus encephalitis is the most common cause of encephalitis worldwide outside the United States. It is a common infection in Japan, China, Southeast Asia, and India.
PLANNING AND IMPLEMENTATION
Collaborative
To maintain a patent airway, many patients require endotracheal intubation, oxygen therapy, and mechanical ventilation if gas exchange is impaired. One of the most important roles of the nurse and physician is ongoing neurological assessment. Using serial assessments, the healthcare team documents changes in the patient's condition and initiates proper care immediately. Pupil size and reaction, level of consciousness, strength and motion of the extremities, and the patient's response to noxious stimuli are all essential for patient assessment and management. Intracranial pressure monitoring may be necessary to manage severe encephalitis. Collect all laboratory samples prior to the start of antiviral agents. Management of fever, pain, and complications such as hypotension, shock, hypoxemia, and seizures is important for recovery.
| Medication or Drug Class | Dosage | Description | Rationale |
|---|
| Antiviral agents | Adults: Acyclovir 10 mg/kg q 8 hr; infuse IV over at least 1 hr for 7–10 days; children: 250 mg/m2 q 8 hr; infuse IV over at least 1 hr for 7–10 days; vidarabine (ARA-A) 15 mg/kg per day infused IV over 12 hr | Interferes with DNA synthesis and viral | Combat herpes simplex encephalitis |
Other Drugs: Foscarnet, an antiviral, may be considered for HIV-positive patients. Patients may receive corticosteroids such as dexamethasone or diuretics such as furosemide to manage brain inflammation, but little data support their use in this situation.
Independent
The maintenance of airway, breathing, and circulation is the foremost concern for the patient with encephalitis. If the patient is unable to clear secretions or maintain a patent airway as the disease progresses, notify the physician immediately and prepare for endotracheal intubation. The family is likely to be anxious and need a great deal of support should intubation and mechanical ventilation be necessary. Once the airway is in place, maintaining an open airway with suctioning as needed is a primary nursing responsibility.
Always take into account patient safety and weigh it against the possibility of the patient's further increase in intracranial pressure. Manage fever and pain to reduce the effects of increased intracranial pressure. Alterations can occur in thought processes when intracranial pressure begins to increase and the level of consciousness begins to decrease. Elevate the head of the bed, keep the neck in appropriate alignment, and perform serial neurological assessments, including pupillary responses. Reorient the patient to time, place, and person as needed. Keep familiar objects or pictures around the patient. Implement measures to limit the effects of immobility, such as skin care, range-of-motion exercises, and a turning and positioning schedule. Note the effect of position changes on intracranial pressure and space activities as necessary.
The patient and significant others need assistance in learning about the disease process and treatments. The patient's behavioral and communication changes are often the most difficult to face and understand. Allow visitation of significant others. Establish alternative means of communication if the patient is unable to maintain verbal contact (e.g., the patient who needs intubation).
Evidence-Based Practice and Health Policy
McKnight, C., Kelly, A., Petrou, M., Nidecker, A., Lorincz, M., Altaee, D., Gebarski, S., & Foerster, B. (2017). A simplified approach to encephalitis and its mimics: Key clinical decision points in the setting of specific imaging abnormalities. Academic Radiology, 24, 667–676.
- The authors aimed to develop a systematic approach that considers both the clinical manifestations and the imaging findings of infectious encephalitis and the diseases it resembles. They sought to determine if the approach can contribute to more accurate and timely diagnosis. They examined their hospital imaging database to generate a list of adult and pediatric patients who had imaging to evaluate possible cases of encephalitis. They combined clinical and imaging findings to generate useful flowcharts, and key imaging features were placed in the context of the flowcharts.
- Four flowcharts based on the primary anatomic site of imaging were created and used to demonstrate similarities and key differences. The authors proposed that the flowcharts could enable clinicians and radiologists to differentiate encephalitis from diseases that mimic the disease, thereby improving patient care.