eMedicine Specialties > Neurology > Neurological Infections

Viral Encephalitis: Follow-up

Author: Francisco de Assis Aquino Gondim, MD, MSc, PhD, Professor Adjunto III, Departments of Physiology and Pharmacology, Neurology Residency Program Director, Faculdade de Medicina, Universidade Federal do Ceará, Brazil
Coauthor(s): Gisele Oliveira, MD, Staff Physician, Department of Neurology, Saint Louis University School of Medicine; Florian P Thomas, MD, MA, PhD, Drmed, Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University
Contributor Information and Disclosures

Updated: Oct 4, 2008

Follow-up

Further Inpatient Care

  • A multidisciplinary approach must be instituted as early as possible to start physical and cognitive rehabilitation and to minimize cognitive problems and long-term sequelae.
  • Care in an ICU setting may be required, especially if seizure activity or increased intracranial pressure is present.

Further Outpatient Care

Outpatient care should be focused on improvement of physical and neurological sequelae.

Inpatient & Outpatient Medications

Patients may need long-term anticonvulsant therapy if seizure activity persists after the acute phase. Accordingly, additional therapy may be necessary for extrapyramidal, motor, and behavioral complications.

Deterrence/Prevention

  • Surveillance is important to predict outbreaks of arboviral infections. Mosquitoes can be sampled to estimate infection rates in mosquito pools. Protective clothing and repellents are useful in the prevention of arthropod bites. Avoidance of outdoor activities is also useful. Prompt removal of ticks may decrease the risk of transmission of a tick-borne virus. Effective preventive measures include removing water-holding containers and discarded tires. Insecticides may be useful in the emergency control of infected mosquitoes. Control of the mosquito vector has been used with apparently good results in several recent epidemics.
  • Vaccines are available for eastern equine encephalitis, western equine encephalitis, and Venezuelan equine encephalitis in horses. A live attenuated vaccine (TC-83) has been used to protect laboratory and field workers from the virus that causes Venezuelan equine encephalitis. Vaccines have also been developed for Japanese B encephalitis and tick-borne encephalitis.
  • Killed virus vaccines have been produced experimentally for several arboviruses. A live-attenuated Japanese B vaccine (SA 14-14-2) has been used widely in Asia. Since 1989, 120 million children have been immunized, and a recent report has demonstrated the efficacy of a single dose in preventing Japanese B encephalitis when administered only days or weeks before exposure to infection. The only internationally licensed Japanese B encephalitis virus vaccine is a formalin-inactivated vaccine. Limited use (eg, in exposed laboratory workers) has been made of vaccines for Venezuelan equine encephalitis and tick-borne viral encephalitis. Passive immunization of laboratory workers exposed to a known virus in a laboratory accident has been accomplished with immune (human) serum or gamma globulin.
  • Despite control efforts and disease surveillance, the 1999 outbreak of West Nile virus in New York, with subsequent spread to other states in the United States, showed that different viruses may be spread in the western hemisphere because of increased international travel and trade. Massive culling of pigs in Malaysia decreased the incidence of Nipah virus infection.

Complications

  • Secondary bacterial infections of the respiratory and urinary tracts are major complications of encephalitis. Complications depend on the severity of the encephalitis and generally decline in importance as the acute illness passes.
  • With recovery from acute viral encephalitis, evidence of neuronal injury and death becomes apparent as residual neurological defects, impairment of intelligence, and psychiatric disturbances. The severity of these sequelae varies according to the causative virus.
  • Sequelae occur in 30-40% of patients aged 5-40 years and include extrapyramidal features (especially dystonia and occasionally parkinsonism), weakness, and seizure disorders. Sequelae are reported in only 3-10% of cases of Japanese B encephalitis in Japan. Yet, 25-30% of young adult males serving in the armed forces of the United States during World War II had sequelae (including neuroses) 6 months after infection. In addition, 10 of 25 individuals who had Japanese B encephalitis in Guam in 1948 had neurological or intellectual defects 10 years later.
  • Hyponatremia due to inappropriate secretion of antidiuretic hormone may be frequent in St. Louis encephalitis. Dehydration, respiratory complications, nosocomial infections, and decubitus ulcers may also occur.
  • See Tables 2-4 for further details on the complications of each viral group.

Prognosis

  • The severity of sequelae apparently varies according to the causative virus.
    • After western equine encephalitis, sequelae are uncommon in adults but are frequent in children. Recurring convulsions with motor or behavioral changes affect more than half of children who are infected when younger than 1 month.
    • With eastern equine encephalitis, most adults older than 40 years who survive (10% mortality rate) do so unscathed; children younger than 5 years have crippling sequelae consisting of mental retardation, convulsions, and paralysis.
    • Permanent sequelae after St. Louis encephalitis are uncommon, except for elderly individuals; the mortality rate is 2% in young adults and 20% in elderly patients.
    • La Crosse virus causes a relatively mild encephalitis with a low fatality rate.
    • Mortality rates are low in Venezuelan equine encephalitis, California encephalitis, and encephalitis due to Colorado tick fever virus. Neurological sequelae in these conditions are not frequent and are usually mild.
    • Japanese B encephalitis has a mortality rate of almost 50% in patients older than 50 years and a mortality rate of less than 20% in children.
    • The Far East form of tick-borne encephalitis is more severe than the Central European form of tick-borne encephalitis, with mortality rates as high as 20% and frequent sequelae. Epilepsia partialis continua may develop during the convalescent period or later. Residual weakness may also be present.
  • The 20-year risk of developing an unprovoked seizure is 22% for patients with viral encephalitis associated with early seizures and 10% for viral encephalitis without early seizures. Of patients with CNS infection, 18-80% develop epilepsy, which is usually refractory to medical treatment. A considerable proportion of such patients develops unilateral mesial temporal lobe epilepsy and can have a good outcome after surgery.
  • The average lifetime cost of the sequelae of encephalitis approaches US $3 million.
  • See Tables 2-4 for further details on the prognosis of each viral group.

Patient Education

Miscellaneous

Medicolegal Pitfalls

  • Delayed diagnosis of HSV encephalitis increases morbidity and mortality rates; failure to diagnose and treat early could result in litigation. With the wide availability of effective therapy, initiating treatment before a definitive diagnosis of HSV encephalitis (ie, during the workup) is now common practice.
  • The belief that HSV-2 lesions initially appear 2 weeks after primary infection can lead to false accusations of infidelity. The physician should emphasize that the initial outbreak of lesions may occur at any time, possibly years, after infection.
 


More on Viral Encephalitis

Overview: Viral Encephalitis
Differential Diagnoses & Workup: Viral Encephalitis
Treatment & Medication: Viral Encephalitis
Follow-up: Viral Encephalitis
References
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Further Reading

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Keywords

encephalitides, herpes simplex virus, HSV, herpesvirus, arbovirus, St Louis encephalitis, eastern equine encephalitis, Japanese B encephalitis, rabies, La Crosse encephalitis, western equine encephalitis, mumps meningoencephalitis, mumps encephalitis, insect vector, mosquito, tick, influenza virus, West Nile virus, dengue fever, enteroviral encephalitis, encephalomyelitis, von Economo encephalitis, encephalitis lethargica, enterovirus 71, rhombencephalitis, Nipah virus, varicella-zoster virus, VZV, lymphocytic choriomeningitis virus, Lassa fever, Venezuelan encephalitis, Far East tick-borne encephalitis, Central European tick-borne encephalitis, Powassan encephalitis, Colorado tick fever, Murray Valley encephalitis, California encephalitis, Jamestown Canyon encephalitis, cytomegalovirus ventriculoencephalitis, CMV

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Contributor Information and Disclosures

Author

Francisco de Assis Aquino Gondim, MD, MSc, PhD, Professor Adjunto III, Departments of Physiology and Pharmacology, Neurology Residency Program Director, Faculdade de Medicina, Universidade Federal do Ceará, Brazil
Francisco de Assis Aquino Gondim, MD, MSc, PhD is a member of the following medical societies: American Academy of Neurology and Movement Disorders Society
Disclosure: Nothing to disclose.

Coauthor(s)

Gisele Oliveira, MD, Staff Physician, Department of Neurology, Saint Louis University School of Medicine
Gisele Oliveira, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.

Florian P Thomas, MD, MA, PhD, Drmed, Director, Spinal Cord Injury Unit, St Louis Veterans Affairs Medical Center; Director, National MS Society Multiple Sclerosis Center; Professor, Department of Neurology and Psychiatry, Associate Professor, Institute for Molecular Virology, and Department of Molecular Microbiology and Immunology, St Louis University
Florian P Thomas, MD, MA, PhD, Drmed is a member of the following medical societies: American Academy of Neurology, American Neurological Association, American Paraplegia Society, and National Multiple Sclerosis Society
Disclosure: Nothing to disclose.

Medical Editor

J Stephen Huff, MD, Associate Professor, Emergency Medicine and Neurology, Department of Emergency Medicine, University of Virginia Health Sciences Center
J Stephen Huff, MD is a member of the following medical societies: American Academy of Emergency Medicine, American Academy of Neurology, American College of Emergency Physicians, and Society for Academic Emergency Medicine
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

James H Halsey, MD, Professor, Department of Neurology, University of Alabama Medical Center
James H Halsey, MD is a member of the following medical societies: American Academy of Neurology, American Heart Association, American Medical Association, American Neurological Association, American Society of Neuroimaging, Medical Association of the State of Alabama, New York Academy of Sciences, Pan American Medical Association, Sigma Xi, Society for Neuroscience, and Southern Medical Association
Disclosure: Nothing to disclose.

CME Editor

Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.

Chief Editor

Nicholas Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.

 
 
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