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NCC0316_Encephalitis_Yogesh.inddEncephalitis
in adults Outcomes in critical care By Vincent M. Vacca, Jr.,
MSN, RN, CCRN, SCRN
Abstract: Encephalitis is defined as inflammation of brain tissue leading to alterations in level of consciousness, cognition, and behavior. Encephalitis can range from mild with full recovery to fulminant leading to death in 4% to 30% of those affected. Approximately one-half of encephalitis survivors have permanent neurologic deficits and require long-term care. Keywords: bacteria, cerebrospinal fluid, encephalitis, inflammation, virus
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Encephalitis is an inflammation of brain tissue that leads to alterations in level of consciousness (LOC), cognition, and behavior. It can also cause fever, headache, seizures, cranial nerve disorders, and motor def- icits, including paralysis. Encephalitis results from various identifiable etiologies, including viruses, bacteria, fungi, parasites, and autoimmune disorders; however, the specific cause remains undetermined in more than 50% of cases.1-5
This article reviews the types, causes, presentation, diagnostics, and treatment of encephalitis with a focus on nursing assessment in the critical care setting.
A global health concern Encephalitis is a major public health concern worldwide. From 1998 to 2010, an estimated 263,352 encephalitis-associated hospitalizations occurred in the United States, and the annual incidence of encephalitis worldwide is estimated to be 0.07 to 12.6 cases per 100,000 people.6-10
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Encephalitis in adults: Outcomes in critical care
Currently, over 20,000 encephalitis-associated hospitalizations occur in the United States each year. However, this number is likely to be signifi- cantly higher because of undiagnosed cases. Encephalitis can range from mild (leading to full recovery) to severe (resulting in permanent disabili- ty) to fulminant (leading to death in 4% to 30% of individuals affected). Approximately one-half of encephalitis survivors will have permanent neuro- logic deficits and require long-term care, which is estimated to cost as much as $3 million per patient over the rest of their lives. The cost to provide care to all individuals in the United States with enceph- alitis-associated hospitalizations in 2010 was approximately $2 billion.6-10
Causes of encephalitis Encephalitis can occur from noninfectious, infec- tious, or postinfectious causes (see Etiologies of infec- tious and noninfectious encephalitis). The most com- mon causes of encephalitis are from viral infections and autoimmune disorders such as Hashimoto encephalopathy.11 Encephalitis can be transmitted: • via airborne droplets from infected persons to noninfected persons • person to person through oral contact • by eating or drinking contaminated food or bever- ages (including water) • via mosquito or tick bites or infected animal bites.12
Regardless of cause, prompt diagnosis and initia- tion of appropriate treatments can improve patient outcomes.4,5,13
Clinical presentation Encephalitis is characterized by inflammation of brain tissue and is almost always accompanied by meningoencephalitis (see Defining terms). Presence of normal brain function is the important distin- guishing feature between encephalitis and meningitis.12 Patients with meningitis may be uncomfortable, lethargic, or distracted by a head- ache, but they retain normal neurologic func- tion.5,12 Encephalopathy may occur with or with- out inflammation of brain tissue. Encephalopathy without inflammation can be triggered by a number of metabolic or toxic conditions such as acute toxic-metabolic encephalopathy.12
Other signs and symptoms secondary to encepha- litis include altered mental status, sensory deficits, behavior and personality changes, and speech or movement disorders. Nuchal rigidity and seizures may also be present. Motor and sensory effects associated with encephalitis may include paresthe- sia and spastic or flaccid paralysis. Patients may also exhibit signs and symptoms such as oliguria, weight gain, hyponatremia, and hypo-osmolality. The lasting effects of encephalitis can include sig- nificant neurologic, motor, sensory, and cognitive deficits.4,5,12
Encephalitis can cause brain tissue edema, resulting in increased intracranial pressure (ICP). Increased ICP can cause brain tissue to shift with- in the skull, resulting in herniation. If severe, her- niation can cause cardiopulmonary dysfunction, which can lead to death. Other complications associated with encephalitis include systemic
Etiologies of infectious and noninfectious encephalitis2,3,5,20,23
Viruses Bacteria Fungi Protozoa Noninfectious
HSV Haemophilus Cryptococcus Plasmodium Allergic reactions infl uenzae neoformans falciparum to vaccinations
WNV Neisseria meningitidis Cryptococcus gattii Acanthamoeba Cancer
JEV Streptococcus Blastomycosis Naegleria Prior exposure pneumoniae to JEV
EEE Mycobacterium Coccidioidomycosis Toxoplasma Chemical exposure tuberculosis gondii including alcohol and
drugs
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disorders that can affect brain function, such as hypoglycemia, fever, and fluid and electrolyte abnormalities. Systemic infections must be consid- ered because they can also be associated with, cause, or worsen encephalitis. An altered LOC can lead to impaired airway protection reflexes that can result in aspiration pneumonia, causing hypoxia. Seizures are common in patients with encephalitis, and status epilepticus associated with encephalitis is present in approximately 15% of patients.13 Mild encephalitis lasts for 7 to 10 days after which a gradual recovery is seen with or without sequelae. Fulminate encephalitis can result in death in 2 to 4 days.2,4,5
Most common types of encephalitis Viral encephalitis. Many viruses are transmitted to humans by arthropods, such as mosquitoes and ticks, and are called arthropod-borne viruses, or arboviruses. Arboviruses include Japanese enceph- alitis virus (JEV), West Nile virus (WNV), Eastern equine encephalitis virus (EEEV), St. Louis encephalitis virus (SLEV), chikungunya virus (CKNV), and others.2 Arbovirus infections such as WNV, EEEV, and SLEV are designated by the Council of State and Territorial Epidemiologists and the CDC as nationally notifiable infectious diseases.4,14
JEV is the leading cause of encephalitis, with an estimated 67,900 annual cases worldwide. The Advisory Committee on Immunization Practices (ACIP) recommends JEV vaccination for all travel- ers who plan to spend 1 month or more in JEV- endemic regions (Asia) during the transmission sea- son (in temperate regions of China, Japan, the Korean peninsula, and eastern parts of Russia, transmission occurs mainly during the summer and fall; it may take place year-round in southeast Asia).15 Since a JEV vaccine was licensed in the United States in 1992, only eight cases of JEV have been reported among U.S. travelers.16 The ACIP also recommends that the JEV vaccine be consid- ered for short-term (less than 1 month) travelers going to rural areas of affected regions whose itiner- aries or activities place them at increased risk for JEV exposure. ACIP also recommends vaccination for short-term travelers going to areas with known outbreaks, and short-term travelers who are unsure of their itineraries.2,17
Defi ning terms Encephalitis: inflammation of brain tissue that leads to alterations in level of consciousness, cognition, and behavior
Encephalopathy: a clinical state of altered mental status, manifesting as confusion, disorientation, behavioral changes, or other cognitive impairments
Meningitis: an inflammatory process limited to the meninges
Meningoencephalitis: inflammation of the brain tissue and adjacent meninges
WNV continues to pose a significant disease bur- den in human populations, with new emerging or reemerging strains. Between 1999 and 2013, more than 39,000 cases of clinical WNV were reported to the CDC. In 2012, the CDC reported the highest number of human WNV cases in the United States since 2003. The majority of individuals present with signs and symptoms such as fatigue, fever, and headache. They may also present with myalgia, muscle weakness, rash, difficulty concentrating, neck pain, arthralgia, gastrointestinal symptoms, photophobia, and maculopapular or morbilliform rash involving the neck, trunk, arms, or legs.18
Approximately 75% of individuals infected with WNV remain asymptomatic. Those who progress to WNV encephalitis present for clinical care with a prolonged altered mental status greater than 24 hours, seizures, and/or focal neurologic abnormalities.4,5
Of the 5,674 cases of WNV reported to the CDC in 2012, 51% were determined to be West Nile neu- roinvasive disease (WNND), amounting to the high- est number of human neuroinvasive cases caused by a mosquito-borne or arbovirus in U.S. history. Prior to 2012, WNND accounted for less than 1% of symptomatic cases per year. WNND is character- ized by meningitis, encephalitis, and/or acute flaccid paralysis, and occurs in 1 in 150 WNV-infected indi- viduals. In 2012, 286 deaths occurred from WNV/ WNND, the most WNV-associated fatalities on record in the United States. Among patients who meet clinical criteria for WNND, acute case fatality is 5% to 10%.13,18-21
Herpes simplex virus type 1 (HSV-1), varicella- zoster virus (VZV), and enterovirus are three of the most commonly identified etiologic agents
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Encephalitis in adults: Outcomes in critical care
associated with acute encephalitis. Herpes is the most common cause of sporadic encephalitis in western countries, with an incidence of approxi- mately two to four cases per million per year. Herpes simplex virus encephalitis (HSE) is the most common nonepidemic form of viral encepha- litis in Western countries.22 Affecting the limbic structures of the brain, HSE causes fever, altera- tions in LOC, personality change, memory dys- function, seizures, and focal neurologic deficits. The most common focal neurologic findings include aphasia, ataxia, involuntary movements including myoclonus, and cranial nerve dysfunc- tion. However, HSV-1 can cause severe necrotizing encephalitis with a high mortality approaching 70% without treatment.19 Clinical presentation, brain imaging such as magnetic resonance imaging (MRI) and cerebral spinal fluid (CSF) analysis, are necessary for the diagnosis of HSE. Unilateral or bilateral temporal lobe involvement is the classic finding of HSE seen on MRI.1,23,24
Because HSV, VZV, and enterovirus are three of the most commonly identified etiologic agents in acute encephalitis, they should be routinely screened for in CSF analysis. If HSE is still suspect- ed despite negative testing from the first CSF analysis, a second CSF analysis should be repeated within 3 to 7 days.13
The prevalence of HSE is not increased in immu- nocompromised hosts, but the presentation may be subacute or atypical in these patients. HSE has a bimodal distribution by age, with the first peak occurring in patients under age 20 and a second peak occurring in patients over age 50. HSE in younger patients usually represents primary infec- tion, whereas HSE in older patients typically reflects reactivation of latent infection. Untreated HSE is progressive and often fatal in 7 to 14 days. Even with treatment, permanent neurologic deficits are com- mon, affecting more than 50% of survivors.8,23,25
Bacterial encephalitis. Rates of bacterial encephali- tis in the United States have declined in the last decade due in large part to highly effective vaccina- tion programs. Because of vaccination, the inci- dence of bacterial encephalitis fell from 0.44 cases per 100,000 between 1998 and 1999 to 0.19 cases between 2006 and 2007.22
Autoimmune encephalitis. Anti-N-methyl-d- aspartate receptor (NMDAR) encephalitis is a severe
but treatable autoimmune disorder defined by the presence of immunoglobulin G in serum and CSF. Anti-NMDAR syndrome is characterized by a promi- nent change in behavior, memory deficits, psychosis, autonomic dysfunction, seizures, abnormal move- ments, and coma. Some patients, mainly young women, harbor an underlying teratoma (germ cell tumors composed of multiple cell types derived from one or more of the three germ layers), usually in the ovary.26 In others, the triggering factor for the NMDAR antibody production is unknown. Prodromal symptoms such as headache, fever, diar- rhea, or upper respiratory symptoms such as hypoventilation requiring mechanical ventilation are frequently reported.17,27
In a large group of patients in whom both CSF and serum were tested for NMDAR antibodies, approximately 15% had positive CSF antibodies in the absence of serum antibodies. Thus, CSF testing by lumbar puncture (LP) is recommended in patients with a compatible clinical picture and neg- ative serum antibodies. Recent evidence has linked the development of antibodies to NMDAR with pre- ceding or concurrent HSE. These reports suggest that patients who experience a neurologic decline following treatment for HSE should also be tested for NMDAR antibodies.17,22,23
Diagnosing encephalitis A thorough health and travel history can help iden- tify potential causes of encephalitis and should include a review of all recent travel, infections, and vaccinations. The history should also include any report of a recent bite from a potentially rabid ani- mal or exposure to mosquitoes, ticks, or rodents. In addition, the season in which illness occurs, and the disease currently prevalent in the community, may provide clues to the diagnosis. (See Encephalitis: Diagnostic criteria.)
Other relevant history that can provide clues to diagnosis include drug and alcohol use, occupa- tional or recreational exposure to rural or outdoor settings (farmers, hunters, campers, forest work- ers), and the immune status of the patient. Although pathologic examination and testing of brain tissue is considered to be the diagnostic gold standard for encephalitis, it is rarely done due to potential morbidity associated with an invasive neurosurgical procedure. In the absence
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of pathologic brain tissue confirmation, encephali- tis is diagnosed on the basis of selected clinical, lab, electroencephalography (EEG), and neuroim- aging features.2 In addition to brain imaging, CSF polymerase chain reaction (PCR) analysis is con- sidered a standard diagnostic study for HSE. The benefit of PCR is that replication of viral DNA can result in both a rapid and specific diagnosis that can facilitate targeted therapies early.3
An LP is the most common approach to access CSF for pressure measurement and sample analy- sis. Prior to performing an LP, evidence of a space- occupying brain lesion causing suspected or known increased ICP should first be ruled out because removal of CSF could precipitate cerebral bleeding or brain herniation.28
Because the spinal cord terminates at the L-2 level, the spinal needle used for an LP enters or punctures the L4-5 intervertebral space to avoid damage to the spinal cord. The subarachnoid space of the lumbar cistern is punctured and accessed. This location is used to both measure spinal fluid opening and closing pressure, and to remove CSF for analysis.29,30
The spinal fluid is normally clear and opening pressure is normally 10 to 20 cm H2O. Elevated opening pressure may contribute to the neurologic dysfunction in encephalitis and must be managed as part of the treatment plan.25
Acute management and goals of care The immediate goals of care are to ensure patient safety along with rapid and accurate diagnosis and appropriate treatment. Assessment and support of airway, breathing, and circulation are an essential first step. The inability to maintain a patent airway and evidence of hypoxemia and/or hypercarbia may necessitate endotracheal intubation with mechanical ventilatory support.6,7
Fever can increase cerebral metabolism, oxygen demand, and accumulation of leukocytes, which also increases with temperature. These changes in inflammatory processes could worsen neurologic condition by disrupting the blood-brain barrier leading to brain tissue edema. Inflammation also increases the viscosity of CSF, which can interfere with absorption, leading to increased ICP, cerebral edema, and hydrocephalus.5,13,31,32 Concerns for ICP elevation and cerebral mass effect due to brain
Encephalitis: Diagnostic criteria3-5,33
Major diagnostic criteria (required):
Altered mental status ≥ 24 hours duration such as altered LOC, lethargy, or personality change
Minor diagnostic criteria (2 required for possible; ≥ 3
required for probable or confi rmed)
• Fever ≥ 38.0° C (100.4° F) within 72 hours before or after presentation
• Generalized or partial seizures not attributable to pre- existing seizure disorder
• New onset of focal neurologic fi ndings • CSF leukocyte count ≥ 5 cells/microL • Abnormality of brain parenchyma on brain imaging
suggestive of encephalitis that is either new or acute • Abnormality on EEG consistent with encephalitis and
not attributable to another cause.
tissue edema from inflammation should prompt rapid bedside assessment and immediate neurolog- ic imaging such as a noncontrast head computed tomography (CT) scan. Rapidly evolving hydro- cephalus, seen on CT scan, typically requires the placement of a ventriculostomy for CSF drainage and ICP monitoring.13
Altered LOC associated with unilateral or bilateral pupillary dilation and sluggish reaction or nonreactivity to light may indicate a neurologic emergency such as transtentorial brain tissue herniation from increased ICP.
A recent review addressed interventions designed to manage acute brain tissue hernia- tion.13 Normal oxygenation (oxygen saturation greater than 90%) and hyperventilation to a PaCO2 of 30 ± 2 mm Hg (normal 35 to 45 mm Hg) and mean arterial pressure of at least 60 mm Hg are recommended. Hyperosmolar therapy with I.V. mannitol or hypertonic saline may also be indicat- ed. When administering I.V. mannitol, it is impor- tant to anticipate and correct subsequent diuresis with 0.9% sodium chloride solution to avoid dehy- dration.13 Head-of-bed elevation to greater than or equal to 30 degrees can be effective in reducing or controlling increased ICP.5,33 Despite interven- tions, brain tissue edema, ICP elevation, and herniation may progress. Initiation of a pharmaco- logic-induced barbiturate coma with endotracheal intubation and mechanical ventilation, if not
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Encephalitis in adults: Outcomes in critical care
already done, or a surgical hemi- craniectomy to relieve global ICP, may be necessary.13
Encephalitis-associated seizure activity can worsen the patient’s neurologic status and should be recognized and treated immedi- ately. EEG monitoring is essen- tial, and continuous EEG (cEEG) is recommended to improve diagnosis and to monitor the effect of antiepileptic drugs (AEDs) in real time.13
For individuals with suspected or diagnosed seizures, first-line benzodiazepine agents such as lorazepam or midazolam are administered. Second-line AEDs, such as fosphenytoin, levetirace- tam, or valproic acid, can be tailored to the specific clinical situation.13
For patients who progress to medically refractory seizures, a third-line AED with anesthetic properties, such as barbiturates including pentobarbital or phenobarbital, or other agents such as propofol or ketamine, may be necessary. Depending on individual response to AEDs, it may be necessary to temporarily induce a pharmacologic burst-suppression pattern on EEG using third-line agents as therapeutic serum levels of second-line AEDs are reached. Burst sup- pression, although not a specific treatment for long-term control of medically refractory seizures, can be beneficial to help recovery after brain inju- ries and to treat epilepsy that is refractory to con- ventional drug therapies.34 On cEEG, burst sup- pression is characterized by alternating patterns of generalized electrical silence, seen as a flat EEG pattern, which is interrupted by generalized bursts of chaotic electrical activity seen as spikes and waves. The goal of burst suppression on cEEG is from one to three bursts every 10 seconds.35
Aggressive seizure treatment and management requires ICU support due to potential complica- tions from the seizure activity or the medications administered to control seizures such as hypoten- sion, loss of protective airway reflexes, and impaired respiratory drive.13
Encephalitis is diagnosed on the basis of selected clinical, lab, EEG, and neuroimaging
features.
Treating encephalitis At time of presentation, it is important to consider empiric and broad-spectrum management for common etiologies of encephalitis. Foremost consideration is for HSV and the need to start I.V. antiviral medication (acyclovir) as early as possible. A delay in I.V. acyclovir treatment in individuals with sus- pected or known HSV-1 infection can result in increased risk of severe permanent disability and death.13
Any suspicion of bacterial infection may necessitate broad- er coverage with appropriate antibiotics and corticosteroids.13
In addition, results of the diag- nostic evaluation may prompt administration of other appropri- ate antibacterial or antifungal agents.
For individuals with an autoimmune etiology, appropriate strategies for immune modulation are indicated. First-line immunotherapies for acute immune-mediated encephalitis generally include corticosteroids, I.V. immunoglobulin (IVIG), and plasmapheresis, either alone or in combination. Response to these agents is typically monitored over several weeks and, if suboptimal, second-line treatments, including cyclophosphamide or ritux- imab, are recommended.10
For anti-NMDAR encephalitis, identification and resection of the offending teratoma is necessary for achieving control of brain tissue inflammation. 13
Empiric immunosuppressive therapy may be con- sidered in patients with encephalitis of unknown etiology. Clinical and/or radiologic deterioration in these patients should prompt consideration of a brain biopsy.10,12,13,17
Nursing considerations Encephalitis and its many potential complications require comprehensive nursing assessment and care. Evaluation of neurologic status using a stan- dardized assessment scale, such as the Glasgow Coma Scale, can provide a baseline to rapidly identify changes. Assess for signs and symptoms
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of increasing ICP such as decreased LOC, dilated pupils, widening pulse pressure, or respiratory pattern irregularity. Prepare patients for diagnostic procedures including LP and neuroimaging studies such as a CT scan, MRI, or neurosurgery.
Notify the healthcare provider of any signs of dete- rioration in clinical status such as fever, mental status changes, seizure activity, or altered respirations. Ensure airway patency and adequate gas exchange. Avoid dehydration and fluid volume overload by assessment of daily weights, intake and output, and central venous pressure measurements, if indicated. Maintain normothermia and manage fever with tem- perature management interventions including anti- pyretics, an external cooling device, or chilled I.V. solutions.
Assess for pain using a standardized pain assess- ment scale appropriate for the patient’s clinical sta- tus. Use a combination of pharmacologic and non- pharmacologic interventions to control pain to a level that is acceptable to the patient. Avoid or limit the use of analgesic or sedative agents that may mask neurologic changes. Darken the room if the patient is experiencing photophobia. Assist with positioning to promote comfort and relief for neck stiffness or pain. Maintain the patient’s head and neck in neutral alignment.
Promote patient safety to decrease the risk of harm or injury. Offer reassurance, redirection, and reorientation. Modify the patient’s surroundings for safety and therapeutic benefit.
Promote nutrition management by assisting with and providing a balanced dietary intake of foods and fluids. Assess the patient’s swallowing ability and consider enteral feedings, if indicat- ed, due to dysphagia and aspiration risk. Encourage active or perform passive range-of- motion exercises and promote early and ongoing mobility progression.
Utilize a standard assessment scale to identify and manage the patient’s risk of pressure ulcers. Maintain skin and mucous membrane integrity. Minimize pressure to body parts through protective body and device positioning.
Provide patient and family education about encephalitis as appropriate. Enforce transmission- based precautions as directed by infection control experts as well as strict hand hygiene for all staff and visitors. Report cases of encephalitis to the
department of public health and the CDC as indicated.4-7
Conclusion Encephalitis remains an important public health issue. Although knowledge of encephalitis has increased substantially, mortality has changed lit- tle across the past two decades. Outcomes of encephalitis vary according to the etiology, timeli- ness of diagnosis, and comorbidities. Viral causes account for the majority of cases in which an etiol- ogy is identified, with a substantial proportion of cases being associated with other specified, pre- dominantly autoimmune, causes. Despite advances in technology and pharmacology, encephalitis remains challenging to diagnose and difficult to treat. The main indicators of poor outcomes asso- ciated with encephalitis include advanced age (age 65 and older) or immunocompromised state (such as from medications, coma, and ICU admission), especially if the patient requires mechanical venti- lation. A specific etiologic agent or process is iden- tified in approximately 50% of encephalitis cases, which points to the need for further research. The mortality of encephalitis is relatively low and near- ly two-thirds of patients achieve a good outcome upon post- hospitalization follow-up. Therefore, aggressive treatment should be pursued even in patients with severe presentation and poor prog- nostic indicators because of the possibility of favorable recovery.1,4,36
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8. Backman R, Foy R, Diggle PJ, et al. The evaluation of a tailored intervention to improve the management of suspected viral enceph- alitis: protocol for a cluster randomised controlled trial. Implement Sci. 2015;10:14.
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17. Höftberger R, Armangue T, Leypoldt F, Graus F, Dalmau J. Clinical Neuropathology practice guide 4-2013: post-herpes simplex encephalitis: N-methyl-Daspartate receptor antibodies are part of the problem. Clin Neuropathol. 2013;32(4):251-254.
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19. Deshpande BR, Rao SR, Jentes ES, et al. Use of Japanese en- cephalitis vaccine in US travel medicine practices in Global TravE- piNet. Am J Trop Med Hyg. 2014;91(4):694-698.
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Vincent M. Vacca, Jr., is a clinical nurse educator, Neuroscience Intensive Care Unit, Brigham & Women’s Hospital, Boston, Mass. He is also a member of the Editorial Advisory Board of Nursing2016 Critical Care.
The author has disclosed that he has no financial relationships related to this article.
DOI-10.1097/01.CCN.0000480745.92978.ea
in adults Outcomes in critical care By Vincent M. Vacca, Jr.,
MSN, RN, CCRN, SCRN
Abstract: Encephalitis is defined as inflammation of brain tissue leading to alterations in level of consciousness, cognition, and behavior. Encephalitis can range from mild with full recovery to fulminant leading to death in 4% to 30% of those affected. Approximately one-half of encephalitis survivors have permanent neurologic deficits and require long-term care. Keywords: bacteria, cerebrospinal fluid, encephalitis, inflammation, virus
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Encephalitis is an inflammation of brain tissue that leads to alterations in level of consciousness (LOC), cognition, and behavior. It can also cause fever, headache, seizures, cranial nerve disorders, and motor def- icits, including paralysis. Encephalitis results from various identifiable etiologies, including viruses, bacteria, fungi, parasites, and autoimmune disorders; however, the specific cause remains undetermined in more than 50% of cases.1-5
This article reviews the types, causes, presentation, diagnostics, and treatment of encephalitis with a focus on nursing assessment in the critical care setting.
A global health concern Encephalitis is a major public health concern worldwide. From 1998 to 2010, an estimated 263,352 encephalitis-associated hospitalizations occurred in the United States, and the annual incidence of encephalitis worldwide is estimated to be 0.07 to 12.6 cases per 100,000 people.6-10
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Encephalitis in adults: Outcomes in critical care
Currently, over 20,000 encephalitis-associated hospitalizations occur in the United States each year. However, this number is likely to be signifi- cantly higher because of undiagnosed cases. Encephalitis can range from mild (leading to full recovery) to severe (resulting in permanent disabili- ty) to fulminant (leading to death in 4% to 30% of individuals affected). Approximately one-half of encephalitis survivors will have permanent neuro- logic deficits and require long-term care, which is estimated to cost as much as $3 million per patient over the rest of their lives. The cost to provide care to all individuals in the United States with enceph- alitis-associated hospitalizations in 2010 was approximately $2 billion.6-10
Causes of encephalitis Encephalitis can occur from noninfectious, infec- tious, or postinfectious causes (see Etiologies of infec- tious and noninfectious encephalitis). The most com- mon causes of encephalitis are from viral infections and autoimmune disorders such as Hashimoto encephalopathy.11 Encephalitis can be transmitted: • via airborne droplets from infected persons to noninfected persons • person to person through oral contact • by eating or drinking contaminated food or bever- ages (including water) • via mosquito or tick bites or infected animal bites.12
Regardless of cause, prompt diagnosis and initia- tion of appropriate treatments can improve patient outcomes.4,5,13
Clinical presentation Encephalitis is characterized by inflammation of brain tissue and is almost always accompanied by meningoencephalitis (see Defining terms). Presence of normal brain function is the important distin- guishing feature between encephalitis and meningitis.12 Patients with meningitis may be uncomfortable, lethargic, or distracted by a head- ache, but they retain normal neurologic func- tion.5,12 Encephalopathy may occur with or with- out inflammation of brain tissue. Encephalopathy without inflammation can be triggered by a number of metabolic or toxic conditions such as acute toxic-metabolic encephalopathy.12
Other signs and symptoms secondary to encepha- litis include altered mental status, sensory deficits, behavior and personality changes, and speech or movement disorders. Nuchal rigidity and seizures may also be present. Motor and sensory effects associated with encephalitis may include paresthe- sia and spastic or flaccid paralysis. Patients may also exhibit signs and symptoms such as oliguria, weight gain, hyponatremia, and hypo-osmolality. The lasting effects of encephalitis can include sig- nificant neurologic, motor, sensory, and cognitive deficits.4,5,12
Encephalitis can cause brain tissue edema, resulting in increased intracranial pressure (ICP). Increased ICP can cause brain tissue to shift with- in the skull, resulting in herniation. If severe, her- niation can cause cardiopulmonary dysfunction, which can lead to death. Other complications associated with encephalitis include systemic
Etiologies of infectious and noninfectious encephalitis2,3,5,20,23
Viruses Bacteria Fungi Protozoa Noninfectious
HSV Haemophilus Cryptococcus Plasmodium Allergic reactions infl uenzae neoformans falciparum to vaccinations
WNV Neisseria meningitidis Cryptococcus gattii Acanthamoeba Cancer
JEV Streptococcus Blastomycosis Naegleria Prior exposure pneumoniae to JEV
EEE Mycobacterium Coccidioidomycosis Toxoplasma Chemical exposure tuberculosis gondii including alcohol and
drugs
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disorders that can affect brain function, such as hypoglycemia, fever, and fluid and electrolyte abnormalities. Systemic infections must be consid- ered because they can also be associated with, cause, or worsen encephalitis. An altered LOC can lead to impaired airway protection reflexes that can result in aspiration pneumonia, causing hypoxia. Seizures are common in patients with encephalitis, and status epilepticus associated with encephalitis is present in approximately 15% of patients.13 Mild encephalitis lasts for 7 to 10 days after which a gradual recovery is seen with or without sequelae. Fulminate encephalitis can result in death in 2 to 4 days.2,4,5
Most common types of encephalitis Viral encephalitis. Many viruses are transmitted to humans by arthropods, such as mosquitoes and ticks, and are called arthropod-borne viruses, or arboviruses. Arboviruses include Japanese enceph- alitis virus (JEV), West Nile virus (WNV), Eastern equine encephalitis virus (EEEV), St. Louis encephalitis virus (SLEV), chikungunya virus (CKNV), and others.2 Arbovirus infections such as WNV, EEEV, and SLEV are designated by the Council of State and Territorial Epidemiologists and the CDC as nationally notifiable infectious diseases.4,14
JEV is the leading cause of encephalitis, with an estimated 67,900 annual cases worldwide. The Advisory Committee on Immunization Practices (ACIP) recommends JEV vaccination for all travel- ers who plan to spend 1 month or more in JEV- endemic regions (Asia) during the transmission sea- son (in temperate regions of China, Japan, the Korean peninsula, and eastern parts of Russia, transmission occurs mainly during the summer and fall; it may take place year-round in southeast Asia).15 Since a JEV vaccine was licensed in the United States in 1992, only eight cases of JEV have been reported among U.S. travelers.16 The ACIP also recommends that the JEV vaccine be consid- ered for short-term (less than 1 month) travelers going to rural areas of affected regions whose itiner- aries or activities place them at increased risk for JEV exposure. ACIP also recommends vaccination for short-term travelers going to areas with known outbreaks, and short-term travelers who are unsure of their itineraries.2,17
Defi ning terms Encephalitis: inflammation of brain tissue that leads to alterations in level of consciousness, cognition, and behavior
Encephalopathy: a clinical state of altered mental status, manifesting as confusion, disorientation, behavioral changes, or other cognitive impairments
Meningitis: an inflammatory process limited to the meninges
Meningoencephalitis: inflammation of the brain tissue and adjacent meninges
WNV continues to pose a significant disease bur- den in human populations, with new emerging or reemerging strains. Between 1999 and 2013, more than 39,000 cases of clinical WNV were reported to the CDC. In 2012, the CDC reported the highest number of human WNV cases in the United States since 2003. The majority of individuals present with signs and symptoms such as fatigue, fever, and headache. They may also present with myalgia, muscle weakness, rash, difficulty concentrating, neck pain, arthralgia, gastrointestinal symptoms, photophobia, and maculopapular or morbilliform rash involving the neck, trunk, arms, or legs.18
Approximately 75% of individuals infected with WNV remain asymptomatic. Those who progress to WNV encephalitis present for clinical care with a prolonged altered mental status greater than 24 hours, seizures, and/or focal neurologic abnormalities.4,5
Of the 5,674 cases of WNV reported to the CDC in 2012, 51% were determined to be West Nile neu- roinvasive disease (WNND), amounting to the high- est number of human neuroinvasive cases caused by a mosquito-borne or arbovirus in U.S. history. Prior to 2012, WNND accounted for less than 1% of symptomatic cases per year. WNND is character- ized by meningitis, encephalitis, and/or acute flaccid paralysis, and occurs in 1 in 150 WNV-infected indi- viduals. In 2012, 286 deaths occurred from WNV/ WNND, the most WNV-associated fatalities on record in the United States. Among patients who meet clinical criteria for WNND, acute case fatality is 5% to 10%.13,18-21
Herpes simplex virus type 1 (HSV-1), varicella- zoster virus (VZV), and enterovirus are three of the most commonly identified etiologic agents
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Encephalitis in adults: Outcomes in critical care
associated with acute encephalitis. Herpes is the most common cause of sporadic encephalitis in western countries, with an incidence of approxi- mately two to four cases per million per year. Herpes simplex virus encephalitis (HSE) is the most common nonepidemic form of viral encepha- litis in Western countries.22 Affecting the limbic structures of the brain, HSE causes fever, altera- tions in LOC, personality change, memory dys- function, seizures, and focal neurologic deficits. The most common focal neurologic findings include aphasia, ataxia, involuntary movements including myoclonus, and cranial nerve dysfunc- tion. However, HSV-1 can cause severe necrotizing encephalitis with a high mortality approaching 70% without treatment.19 Clinical presentation, brain imaging such as magnetic resonance imaging (MRI) and cerebral spinal fluid (CSF) analysis, are necessary for the diagnosis of HSE. Unilateral or bilateral temporal lobe involvement is the classic finding of HSE seen on MRI.1,23,24
Because HSV, VZV, and enterovirus are three of the most commonly identified etiologic agents in acute encephalitis, they should be routinely screened for in CSF analysis. If HSE is still suspect- ed despite negative testing from the first CSF analysis, a second CSF analysis should be repeated within 3 to 7 days.13
The prevalence of HSE is not increased in immu- nocompromised hosts, but the presentation may be subacute or atypical in these patients. HSE has a bimodal distribution by age, with the first peak occurring in patients under age 20 and a second peak occurring in patients over age 50. HSE in younger patients usually represents primary infec- tion, whereas HSE in older patients typically reflects reactivation of latent infection. Untreated HSE is progressive and often fatal in 7 to 14 days. Even with treatment, permanent neurologic deficits are com- mon, affecting more than 50% of survivors.8,23,25
Bacterial encephalitis. Rates of bacterial encephali- tis in the United States have declined in the last decade due in large part to highly effective vaccina- tion programs. Because of vaccination, the inci- dence of bacterial encephalitis fell from 0.44 cases per 100,000 between 1998 and 1999 to 0.19 cases between 2006 and 2007.22
Autoimmune encephalitis. Anti-N-methyl-d- aspartate receptor (NMDAR) encephalitis is a severe
but treatable autoimmune disorder defined by the presence of immunoglobulin G in serum and CSF. Anti-NMDAR syndrome is characterized by a promi- nent change in behavior, memory deficits, psychosis, autonomic dysfunction, seizures, abnormal move- ments, and coma. Some patients, mainly young women, harbor an underlying teratoma (germ cell tumors composed of multiple cell types derived from one or more of the three germ layers), usually in the ovary.26 In others, the triggering factor for the NMDAR antibody production is unknown. Prodromal symptoms such as headache, fever, diar- rhea, or upper respiratory symptoms such as hypoventilation requiring mechanical ventilation are frequently reported.17,27
In a large group of patients in whom both CSF and serum were tested for NMDAR antibodies, approximately 15% had positive CSF antibodies in the absence of serum antibodies. Thus, CSF testing by lumbar puncture (LP) is recommended in patients with a compatible clinical picture and neg- ative serum antibodies. Recent evidence has linked the development of antibodies to NMDAR with pre- ceding or concurrent HSE. These reports suggest that patients who experience a neurologic decline following treatment for HSE should also be tested for NMDAR antibodies.17,22,23
Diagnosing encephalitis A thorough health and travel history can help iden- tify potential causes of encephalitis and should include a review of all recent travel, infections, and vaccinations. The history should also include any report of a recent bite from a potentially rabid ani- mal or exposure to mosquitoes, ticks, or rodents. In addition, the season in which illness occurs, and the disease currently prevalent in the community, may provide clues to the diagnosis. (See Encephalitis: Diagnostic criteria.)
Other relevant history that can provide clues to diagnosis include drug and alcohol use, occupa- tional or recreational exposure to rural or outdoor settings (farmers, hunters, campers, forest work- ers), and the immune status of the patient. Although pathologic examination and testing of brain tissue is considered to be the diagnostic gold standard for encephalitis, it is rarely done due to potential morbidity associated with an invasive neurosurgical procedure. In the absence
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of pathologic brain tissue confirmation, encephali- tis is diagnosed on the basis of selected clinical, lab, electroencephalography (EEG), and neuroim- aging features.2 In addition to brain imaging, CSF polymerase chain reaction (PCR) analysis is con- sidered a standard diagnostic study for HSE. The benefit of PCR is that replication of viral DNA can result in both a rapid and specific diagnosis that can facilitate targeted therapies early.3
An LP is the most common approach to access CSF for pressure measurement and sample analy- sis. Prior to performing an LP, evidence of a space- occupying brain lesion causing suspected or known increased ICP should first be ruled out because removal of CSF could precipitate cerebral bleeding or brain herniation.28
Because the spinal cord terminates at the L-2 level, the spinal needle used for an LP enters or punctures the L4-5 intervertebral space to avoid damage to the spinal cord. The subarachnoid space of the lumbar cistern is punctured and accessed. This location is used to both measure spinal fluid opening and closing pressure, and to remove CSF for analysis.29,30
The spinal fluid is normally clear and opening pressure is normally 10 to 20 cm H2O. Elevated opening pressure may contribute to the neurologic dysfunction in encephalitis and must be managed as part of the treatment plan.25
Acute management and goals of care The immediate goals of care are to ensure patient safety along with rapid and accurate diagnosis and appropriate treatment. Assessment and support of airway, breathing, and circulation are an essential first step. The inability to maintain a patent airway and evidence of hypoxemia and/or hypercarbia may necessitate endotracheal intubation with mechanical ventilatory support.6,7
Fever can increase cerebral metabolism, oxygen demand, and accumulation of leukocytes, which also increases with temperature. These changes in inflammatory processes could worsen neurologic condition by disrupting the blood-brain barrier leading to brain tissue edema. Inflammation also increases the viscosity of CSF, which can interfere with absorption, leading to increased ICP, cerebral edema, and hydrocephalus.5,13,31,32 Concerns for ICP elevation and cerebral mass effect due to brain
Encephalitis: Diagnostic criteria3-5,33
Major diagnostic criteria (required):
Altered mental status ≥ 24 hours duration such as altered LOC, lethargy, or personality change
Minor diagnostic criteria (2 required for possible; ≥ 3
required for probable or confi rmed)
• Fever ≥ 38.0° C (100.4° F) within 72 hours before or after presentation
• Generalized or partial seizures not attributable to pre- existing seizure disorder
• New onset of focal neurologic fi ndings • CSF leukocyte count ≥ 5 cells/microL • Abnormality of brain parenchyma on brain imaging
suggestive of encephalitis that is either new or acute • Abnormality on EEG consistent with encephalitis and
not attributable to another cause.
tissue edema from inflammation should prompt rapid bedside assessment and immediate neurolog- ic imaging such as a noncontrast head computed tomography (CT) scan. Rapidly evolving hydro- cephalus, seen on CT scan, typically requires the placement of a ventriculostomy for CSF drainage and ICP monitoring.13
Altered LOC associated with unilateral or bilateral pupillary dilation and sluggish reaction or nonreactivity to light may indicate a neurologic emergency such as transtentorial brain tissue herniation from increased ICP.
A recent review addressed interventions designed to manage acute brain tissue hernia- tion.13 Normal oxygenation (oxygen saturation greater than 90%) and hyperventilation to a PaCO2 of 30 ± 2 mm Hg (normal 35 to 45 mm Hg) and mean arterial pressure of at least 60 mm Hg are recommended. Hyperosmolar therapy with I.V. mannitol or hypertonic saline may also be indicat- ed. When administering I.V. mannitol, it is impor- tant to anticipate and correct subsequent diuresis with 0.9% sodium chloride solution to avoid dehy- dration.13 Head-of-bed elevation to greater than or equal to 30 degrees can be effective in reducing or controlling increased ICP.5,33 Despite interven- tions, brain tissue edema, ICP elevation, and herniation may progress. Initiation of a pharmaco- logic-induced barbiturate coma with endotracheal intubation and mechanical ventilation, if not
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Encephalitis in adults: Outcomes in critical care
already done, or a surgical hemi- craniectomy to relieve global ICP, may be necessary.13
Encephalitis-associated seizure activity can worsen the patient’s neurologic status and should be recognized and treated immedi- ately. EEG monitoring is essen- tial, and continuous EEG (cEEG) is recommended to improve diagnosis and to monitor the effect of antiepileptic drugs (AEDs) in real time.13
For individuals with suspected or diagnosed seizures, first-line benzodiazepine agents such as lorazepam or midazolam are administered. Second-line AEDs, such as fosphenytoin, levetirace- tam, or valproic acid, can be tailored to the specific clinical situation.13
For patients who progress to medically refractory seizures, a third-line AED with anesthetic properties, such as barbiturates including pentobarbital or phenobarbital, or other agents such as propofol or ketamine, may be necessary. Depending on individual response to AEDs, it may be necessary to temporarily induce a pharmacologic burst-suppression pattern on EEG using third-line agents as therapeutic serum levels of second-line AEDs are reached. Burst sup- pression, although not a specific treatment for long-term control of medically refractory seizures, can be beneficial to help recovery after brain inju- ries and to treat epilepsy that is refractory to con- ventional drug therapies.34 On cEEG, burst sup- pression is characterized by alternating patterns of generalized electrical silence, seen as a flat EEG pattern, which is interrupted by generalized bursts of chaotic electrical activity seen as spikes and waves. The goal of burst suppression on cEEG is from one to three bursts every 10 seconds.35
Aggressive seizure treatment and management requires ICU support due to potential complica- tions from the seizure activity or the medications administered to control seizures such as hypoten- sion, loss of protective airway reflexes, and impaired respiratory drive.13
Encephalitis is diagnosed on the basis of selected clinical, lab, EEG, and neuroimaging
features.
Treating encephalitis At time of presentation, it is important to consider empiric and broad-spectrum management for common etiologies of encephalitis. Foremost consideration is for HSV and the need to start I.V. antiviral medication (acyclovir) as early as possible. A delay in I.V. acyclovir treatment in individuals with sus- pected or known HSV-1 infection can result in increased risk of severe permanent disability and death.13
Any suspicion of bacterial infection may necessitate broad- er coverage with appropriate antibiotics and corticosteroids.13
In addition, results of the diag- nostic evaluation may prompt administration of other appropri- ate antibacterial or antifungal agents.
For individuals with an autoimmune etiology, appropriate strategies for immune modulation are indicated. First-line immunotherapies for acute immune-mediated encephalitis generally include corticosteroids, I.V. immunoglobulin (IVIG), and plasmapheresis, either alone or in combination. Response to these agents is typically monitored over several weeks and, if suboptimal, second-line treatments, including cyclophosphamide or ritux- imab, are recommended.10
For anti-NMDAR encephalitis, identification and resection of the offending teratoma is necessary for achieving control of brain tissue inflammation. 13
Empiric immunosuppressive therapy may be con- sidered in patients with encephalitis of unknown etiology. Clinical and/or radiologic deterioration in these patients should prompt consideration of a brain biopsy.10,12,13,17
Nursing considerations Encephalitis and its many potential complications require comprehensive nursing assessment and care. Evaluation of neurologic status using a stan- dardized assessment scale, such as the Glasgow Coma Scale, can provide a baseline to rapidly identify changes. Assess for signs and symptoms
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of increasing ICP such as decreased LOC, dilated pupils, widening pulse pressure, or respiratory pattern irregularity. Prepare patients for diagnostic procedures including LP and neuroimaging studies such as a CT scan, MRI, or neurosurgery.
Notify the healthcare provider of any signs of dete- rioration in clinical status such as fever, mental status changes, seizure activity, or altered respirations. Ensure airway patency and adequate gas exchange. Avoid dehydration and fluid volume overload by assessment of daily weights, intake and output, and central venous pressure measurements, if indicated. Maintain normothermia and manage fever with tem- perature management interventions including anti- pyretics, an external cooling device, or chilled I.V. solutions.
Assess for pain using a standardized pain assess- ment scale appropriate for the patient’s clinical sta- tus. Use a combination of pharmacologic and non- pharmacologic interventions to control pain to a level that is acceptable to the patient. Avoid or limit the use of analgesic or sedative agents that may mask neurologic changes. Darken the room if the patient is experiencing photophobia. Assist with positioning to promote comfort and relief for neck stiffness or pain. Maintain the patient’s head and neck in neutral alignment.
Promote patient safety to decrease the risk of harm or injury. Offer reassurance, redirection, and reorientation. Modify the patient’s surroundings for safety and therapeutic benefit.
Promote nutrition management by assisting with and providing a balanced dietary intake of foods and fluids. Assess the patient’s swallowing ability and consider enteral feedings, if indicat- ed, due to dysphagia and aspiration risk. Encourage active or perform passive range-of- motion exercises and promote early and ongoing mobility progression.
Utilize a standard assessment scale to identify and manage the patient’s risk of pressure ulcers. Maintain skin and mucous membrane integrity. Minimize pressure to body parts through protective body and device positioning.
Provide patient and family education about encephalitis as appropriate. Enforce transmission- based precautions as directed by infection control experts as well as strict hand hygiene for all staff and visitors. Report cases of encephalitis to the
department of public health and the CDC as indicated.4-7
Conclusion Encephalitis remains an important public health issue. Although knowledge of encephalitis has increased substantially, mortality has changed lit- tle across the past two decades. Outcomes of encephalitis vary according to the etiology, timeli- ness of diagnosis, and comorbidities. Viral causes account for the majority of cases in which an etiol- ogy is identified, with a substantial proportion of cases being associated with other specified, pre- dominantly autoimmune, causes. Despite advances in technology and pharmacology, encephalitis remains challenging to diagnose and difficult to treat. The main indicators of poor outcomes asso- ciated with encephalitis include advanced age (age 65 and older) or immunocompromised state (such as from medications, coma, and ICU admission), especially if the patient requires mechanical venti- lation. A specific etiologic agent or process is iden- tified in approximately 50% of encephalitis cases, which points to the need for further research. The mortality of encephalitis is relatively low and near- ly two-thirds of patients achieve a good outcome upon post- hospitalization follow-up. Therefore, aggressive treatment should be pursued even in patients with severe presentation and poor prog- nostic indicators because of the possibility of favorable recovery.1,4,36
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Vincent M. Vacca, Jr., is a clinical nurse educator, Neuroscience Intensive Care Unit, Brigham & Women’s Hospital, Boston, Mass. He is also a member of the Editorial Advisory Board of Nursing2016 Critical Care.
The author has disclosed that he has no financial relationships related to this article.
DOI-10.1097/01.CCN.0000480745.92978.ea