Encephalitis

Encephalitis: Excerpt from The 5-Minute Pediatric Consult

A. G. Christina Bergqvist, MD

Encephalitis - BASICS

Encephalitis - description

Inflammation of the brain parenchyma owing to infection. Meningoencephalitis is inflammation of the brain and the meninges.

Encephalitis - general prevention

• Completion of routine immunizations (varicella) and routine hygiene (hand washing) are the best preventive measures.
• Other measures should be taken according to the infection (e.g., insect repellent, skin testing contacts in cases of tuberculosis).
• Isolation of hospitalized patient:
  • Depends on organism suspected
  • Airborne, droplet, and contact precautions are frequently used together during the 1st 24 hours, pending a more specific diagnosis from cultures.
  • The hospital infectious disease department determines isolation procedures and whether family members need to be treated.

Encephalitis - epidemiology

Encephalitis - incidence

Varies with age, geographic location, and season

Encephalitis - pathophysiology

• Direct or delayed (postinfectious) reaction by the immune system to a virus, bacteria, fungus, or parasite
• Organisms enter the CNS via the systemic circulation, direct inoculation (trauma), or neural pathways (rabies, herpes simplex virus [HSV]).
• Infiltration/activation of inflammatory cells in the CNS with release of cytokines
• Inclusion bodies (intranuclear, HSV, subacute sclerosing panencephalitis [SSPE], viral, intracytoplasmic, rabies); CSF; and serological changes

Encephalitis - etiology

• The most common causes of encephalitis are viruses:
  • Summer (enteroviruses)
  • Summer and fall (western and eastern equine, St. Louis, La Crosse, and West Nile encephalitis)
  • Winter (varicella)
• Nonviral causes (tuberculosis, Lyme disease, toxoplasmosis, cat scratch disease, rickettsial disease, tick-borne infections) are sometimes associated with specific environmental or geographic exposure.
• The most common cause of sporadic encephalitis is HSV (rabies and HIV also occur in all seasons).

Encephalitis - DIAGNOSIS

Encephalitis - signs & symptoms

Encephalitis - history

• Ask about a viral prodrome with symptoms such as upper respiratory infection, cough, coryza, malaise, anorexia, decreased enteral intake, diarrhea, nausea, and vomiting.
• Encephalitis is often heralded by headaches, photophobia, a stiff neck, increased sleeping, change in mental status, irritability, confusion, hallucinations, seizures.
• Prodromal symptoms can range from hours to weeks; seizures or sudden lapse of consciousness are uncommon as initial symptoms of encephalitis.
• Inquire about recent travel history, pets, and tick or mosquito bites.

Encephalitis - physical exam

• Hypertension, bradycardia, or apnea may suggest impending herniation owing to brain swelling.
• Neck: Meningismus, Kernig/Brudzinski signs
• Adenopathy (Mycobacterium, cat scratch encephalitis [Bartonella])
• Chest: Signs of pneumonia, rales, rhonchi (especially with Mycobacterium and Mycoplasma infections and influenza)
• Abdomen: Hepatosplenomegaly (Epstein–Barr virus [EBV], Ehrlichia)
• Skin: May show various types of rashes, from petechial (rickettsial infection, meningococcemia) to erythematous or papular (especially with Lyme disease, Enterovirus infection)
• Neurologic exam: Mental status ranging from mild confusion to delirium with hallucinations to stupor and coma
• Aphasia (suggestive of herpes) is distinguished from psychomotor slowing by prominence of grammatical errors and dysarthria with normal alertness.
• Cranial nerves-facial palsy, papilledema, nystagmus
• Increased muscle tone, pathologic deep tendon reflexes, Babinski sign, clonus, or ataxia (especially with varicella)
• Flaccid paralysis or a poliolike syndrome: Seen with West Nile virus

Encephalitis - tests

• Testing strategies depend on the severity of symptoms.
• EEG:
  • Particularly if HSV is suspected
  • Periodic lateralizing epileptiform discharges (PLEDs) are suggestive but not diagnostic of herpes.
  • Continuous monitoring for comatose patients with known seizures

Encephalitis - lab

• Blood electrolytes, glucose, BUN, creatinine
• Liver enzymes, calcium, magnesium, phosphorus
• Blood count with differential
• Blood and urine culture
• Serological testing (usually sent out to a specialized virology lab)
• Toxicology screen
• Purified protein derivative (PPD) if CSF or other signs suggest the possibility of Mycobacterium

Encephalitis - imaging

CT or MRI of the brain with and without contrast medium:

• Perform urgently to rule out surgically remediable conditions (empyema, abscess).
• Typical changes in encephalitis include parenchymal, meningeal, and focal or diffuse enhancement of the brain. (HSV has a preference for the medial temporal lobe.)
• Hydrocephalus, obstructive or communicating, may occur weeks following the encephalitis.

Encephalitis - diag proced-surgery

Lumbar puncture:

• Defer until airway, gas exchange, and circulation have been stabilized.
• Thereafter, defer if there is papilledema or if imaging shows subfalcine herniation (left-to-right shift of lateral ventricles), cerebral edema, obstructive hydrocephalus (lateral ventricles large, fourth ventricle relatively small), or central herniation (asymmetry or effacement of fourth ventricle/basilar cistern).
• Perform if there is no papilledema or radiologic evidence for increased intracranial pressure:
  • Opening pressure is frequently elevated.
  • Pleocytosis is lymphocytic if viral and usually neutrophilic if bacterial.
  • Protein will be increased, glucose will be variably decreased, and red blood cells (RBCs) may be present (particularly in HSV).
  • Send CSF for bacterial and viral culture; fungal culture if suspected.
  • If HSV is suspected, obtain polymerase chain reaction (PCR) assay. Other PCR-based tests on CSF, including assays for the Lyme spirochete, enteroviruses, and West Nile virus, may be considered.
  • Order Gram stain and acid–fast bacillus, cryptococcal antigen, and yeast tests.
  • State and local departments of health are often helpful in planning and handling extended virologic studies.

• A CSF sample without any RBCs does not rule out HSV.
• Never assume that a CSF pleocytosis is secondary to seizures. Institute antiviral and/or antibacterial therapy promptly; it can always be discontinued after an organism is identified or cultures are negative.
• Children with immunodeficiency are at higher risk for fungal meningoencephalitis, which may be missed unless appropriate studies are sent.
• Amebic infection of the brain should be considered in children with exposure to fresh water sources.
• Cysticercosis is common in tropical and underdeveloped areas. Ring-enhancing lesions may point to this diagnosis or to toxoplasmosis.

Encephalitis - differencial diagnosis

Several toxic, metabolic, vascular, and epileptic syndromes may resemble encephalitis. Diagnosis of specific causes of true encephalitis depends on geographic location, age, and clinical and associated laboratory findings:

• Ingestions
• Hypothyroid crisis
• Acute electrolyte disturbance, especially hyponatremia
• Reye syndrome
• Noninfectious encephalitides triggered by immunization or infection include acute hemorrhagic leukoencephalitis and acute disseminated encephalomyelitis (associated Mycoplasma, EBV, or other infection), in context of acute rheumatic fever (rare).
• Intracranial hemorrhage
• Pituitary infarction
• Acute obstructive hydrocephalus or ventriculoperitoneal shunt obstruction
• Sinus thrombosis
• Subdural empyema
• Cerebral vasculitis, stroke, or septic embolization (endocarditis)
• Brain abscess or subdural empyema
• Malignant hyperthermia
• Status epilepticus
• Meningitis:
  • Bacterial (Neisseria meningitidis, Haemophilus influenzae type b, group B streptococcus in the neonate, Escherichia coli in the neonate)
  • May cause secondary parenchymal inflammation of the brain
  • Mental status changes are more prominent in primary encephalitis than in meningitis.
• Microbes to consider:
  • Herpesviruses (in the child and adult, herpes has preference for the medial temporal lobe)
  • Lyme disease; possible coinfection with Ehrlichia, Babesia
  • Varicella (postinfectious or primary varicella infection)
  • Cat scratch and rickettsial diseases
  • Leptospirosis
  • Tuberculosis
  • Fungal (cryptosporidiosis)
  • Parasitic (Amoeba, Toxoplasma, Schistosoma, cysticercosis)

Encephalitis - TREATMENT

Encephalitis - initial stabilization

Patients frequently require ICU care with cardiorespiratory support. Minidose subcutaneous heparin is standard for prophylaxis of intravascular thrombosis in acutely ill adults, but is untested in the pediatric age group. Early involvement of physical and occupational therapy is important.

Encephalitis - general measures

• Treatment of intracranial hypertension includes mannitol and hyperventilation, usually with assistance from intensivists or neurology/neurosurgery consultants; these measures should be reserved for situations in which vital or neurologic signs indicate impending herniation. Intracranial pressure monitoring is not routinely indicated.
• Consultation with an infectious disease specialist, neurologist, or neurosurgeon may be helpful.

Encephalitis - special therapy

Encephalitis - iv fluids

• Avoid fluid overload, which may exacerbate cerebral edema.
• Requires strict attention to fluid/osmotic balance
• Normal saline is preferred.
• Closely monitor electrolytes, anticipating possible syndrome of inappropriate antidiuretic hormone or diabetes insipidus.

Encephalitis - medication

• Anti-infective agents:
  • Depending on severity of the illness and clinician’s level of suspicion
  • Initial treatment could include antibacterial and antiviral agents (acyclovir: Monitor renal function) until the cause becomes clear or cultures are negative.
• Confirmed HSV encephalitis: Acyclovir:
  • Infants: 20 mg/kg q8h for 21 days
  • Older children: 10 mg/kg q8h for 10–14 days
• Cytomegalovirus (CMV): Consider ganciclovir or foscarnet.
• HIV encephalitis: Consider zidovudine, didanosine, or ritonavir.
• SSPE (diagnosed by spinal fluid titers): Consider isoprinosine.
• Anticonvulsants:
  • Reserved for clinical or electrographic evidence of seizure/epileptic activity
  • Usual choices include lorazepam, phenytoin, phenobarbital, and carbamazepine.
  • Treatment of PLEDs without associated convulsions is controversial.
  • Consider potential side effects and sedation.

Encephalitis - FOLLOW UP

• Outcome varies greatly and depends on age and degree of CNS involvement.
• Physical and occupational therapists should be consulted early in the course.
• Neuropsychologic testing is helpful to identify cognitive deficits and to maximize the patient’s recovery.

Encephalitis - prognosis

Outcome ranges from complete recovery to coma, persistent vegetative state, and death.

Encephalitis - complications

• Seizure disorders, focal or generalized
• Quadriparesis/hemiparesis
• Ataxia
• Learning disabilities
• Aphasias

Encephalitis - bibliography

1. Chang LY, Huang LM, Gau SS, et al. Neurodevelopment and cognition in children after enterovirus 71 infection. N Engl J Med. 2007;356(12):1226–1234.
2. Elbers JM, Bitnun A, Richardson SE, et al. A 12-year prospective study of childhood herpes simplex encephalitis: Is there a broader spectrum of disease? Pediatrics. 2007;119(2):e399–e407.
3. McGovern LM, Boyce TG, Fischer PR. Congenital infections associated with international travel during pregnancy. J Travel Med. 2007;14(2):117–128.
4. Miravet E, Danchaivijitr N, Basu H, et al. Clinical and radiological features of childhood cerebral infarction following varicella zoster virus infection. Dev Med Child Neurol. 2007;49(6):417–422.
5. Redington J, Tyler K. Viral infections of the nervous system, 2002: Update on diagnosis and treatment. Arch Neurol. 2002;59:712–718.
6. Sampathkumar P. West Nile virus: Epidemiology, clinical presentation, diagnosis, and prevention. Mayo Clin Proc. 2003;78:1137–1144.
7. Silvia MT. Licht DJ. Pediatric central nervous system infections and inflammatory white matter disease. Pediatr Clin North Am. 2005;52:1107–1126.
8. Tenembaum S, Chitnis T, Ness J, et al. International Pediatric MS Study Group. Acute disseminated encephalomyelitis. Neurology. 2007;68:S23–S36.

Encephalitis - CODES

Encephalitis - icd9

323.9 Unspecified cause of encephalitis

Encephalitis - PATIENT TEACHING-MED

• From Boston Children’s Hospital: http://www.childrenshospital.org/az/Site832/mainpageS832P0.html
• National Center for Infectious Diseases. Patient information. Available at: http://www.cdc.gov/ncidod

Encephalitis - FAQ

• Q: My child has been diagnosed with encephalitis; will he be mentally retarded?
• A: The complications following encephalitis vary greatly from severe mental retardation and cerebral palsy to full recovery. There is a correlation between degree of brain destruction and outcome; however, children frequently recover better than adults with a similar degree of illness.

Book Source Details

• Book Title: The 5-Minute Pediatric Consult
• Author(s): M. William Schwartz MD; et al.
• Year of Publication: 2008
• Copyright Details: The 5-Minute Pediatric Consult, Copyright © 2008 Lippincott Williams & Wilkins.

More About Arachnoiditis

• Back to disease: Arachnoiditis: Introduction
• Next Book Extract About Arachnoiditis: Surveys relating to Arachnoiditis
• More Book Extracts: All Online Books for Arachnoiditis

More Medical Textbooks Online about Arachnoiditis

Review other book chapters online related to Arachnoiditis:

Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: The 5-Minute Pediatric Consult Authors: M. William Schwartz MD; et al. Publisher: Lippincott Williams & Wilkins Copyright: 2008 ISBN: 0-7817-7577-9

 » Next page: Surveys relating to Arachnoiditis

Rate This Website

What do you think about the features of this website? Take our user survey and have your say:

Website User Survey

Medical Tools & Articles:

Next articles:

• Surveys relating to Arachnoiditis
• Ask Question about Arachnoiditis

Tools & Services:

• Bookmark this page
• Symptom Search
• Symptom Checker
• Medical Dictionary
• Give your feedback

Medical Articles:

• Disease & Treatments Search
• Misdiagnosis Center
• Full list of interesting articles

Forums & Message Boards

• Ask or answer a question at the Boards:
• I cannot get a diagnosis. Please help.
• Tell us your medical story.
• Share your misdiagnosis story.
• What is the best treatment for my condition?
• See all the Boards.

Enter your search terms Submit search form
Search The Web Search wrongdiagnosis.com

Common Health Mistakes

Symptom
Checker

Search Specialists by State and City