3. Introduction
• Encephalitis is defined as inflammation of the brain parenchyma
associated with neurologic dysfunction
• Acute encephalitis associated with viral infections includes 2 distinct
clinical-pathological diseases.
ACUTE VIRAL ENCEPHALITIS
Postinfectious encephalomyelitis
• Acute viral encephalitis is due to direct effects of acute infections on
the brain
5. Introduction
WHO Clinical case definition of acute encephalitis syndrome
• Person of any age, at any time of year, with
• Acute onset of fever AND
• Change in mental status (including symptoms such as confusion,
disorientation, coma, or inability to talk) AND/OR
• New onset of seizures (excluding simple febrile seizures)
• Other early clinical findings can include an increase in irritability,
somnolence or abnormal behaviour greater than that seen with usual
febrile illness
6. Epidemiology
• Acute viral encephalitis is of public health concern worldwide because
of its high morbidity and mortality
• Incidence of 5-10 per 100 000/year
• Commoner in children and the elderly
• Slight predominance in males
• Paucity of data in Nigerian
13. Pathogenesis
Immunopathology
• Cytotoxic T cells & phagocytic macrophages act as effectors
• Interferons (α, β, and γ) and their regulatory transacting proteins may
act to limit CNS virus replication
• IL-1β, IL-6, and TNF-α are injurious
14. Pathogenesis
• Specific sites of viral predilection
Temporal and inferior frontal lobes (HSV)
Periventricular areas (CMV)
Limbic system (RV)
Cerebellum (VZV)
Basal ganglia (JEV)
15. Clinical manifestation
• Severity of deficits range from very mild to extreme
• Progressive constellation of symptoms evolves over a period of days
Acute febrile illness
Frequent meningeal involvement (headache, neck stiffness)
Brain parenchymal involvement
18. Case presentation
• A 35-year-old man presented to A/E with 3 days of low-grade fever
• He awoke at 2:00 AM on the fourth day, got dressed, went to the
kitchen, poured cereal onto the kitchen table, added milk, got the car
keys, and promptly packed his car across the garage door. At that
point, his wife immediately took him to A/E
• He had no witnessed seizures
• Temp in A/E was 38.5◦C; he was normotensive
• On neurologic examination, he had an expressive aphasia
• No focal signs of weakness at presentation
19. Case presentation
oComment
• This case is a classic presentation for HS encephalitis
• It is now the responsibility of the A/E physician or neurologist to
define a course of action
• First, a working differential diagnosis must be established
• Numerous diseases mimic HS encephalitis; most are not treatable
• Clearly, the expressive aphasia points to focal neurologic process
24. Investigations/Diagnosis
Diagnostic Criteria for Acute Encephalitis
Major Criterion (required):
Altered mental status (decreased/altered level of consciousness,
lethargy or personality change) ≥24hrs, no alternative cause identified
Minor Criteria
• 2 for possible encephalitis
• ≥3 for probable or confirmed encephalitis
26. Investigations/Diagnosis
Minor Criteria
CSF WBC count ≥5/mm³
Neuroimaging suggestive of encephalitis either new from prior studies
or appears acute in onset
Abnormality on EEG consistent with encephalitis and not attributable
to another cause
28. Treatment
• 3 “Es”: emergent issues, epilepsy, and etiology
Emergent issues
ABC of resuscitation
Consider admission to ICU
Fluid restriction
Avoidance of hypotonic intravenous solutions
Suppression of fever
Management of raised ICP
29. Treatment
Hyperventilation to pCO2 30+/-2mmHg & MAP ≥60mmHg
Mannitol 0.25-1g/kg bolus every 4-6 hours
Hypertonic saline
• Active brain herniation: 23.4% saline (30 mL bolus via CV line)
• Maintenance 2%-3% saline (250-500 mL boluses or continuous
venous infusion; 3% saline via CV line)
30. Treatment
Seizures
Aetiology
• Acyclovir, 10 mg/kg IV q 8 hrs x 14-21 days
• Oral acyclovir, famciclovir, and valacyclovir (efficacy against HSV,
VZV, EBV) have not been evaluated in the treatment of encephalitis
either as primary therapy or as supplemental therapy
• IV ribavirin 15-25 mg/kg/day in divided doses every 8 hrs
36. Conclusion
• Acute viral encephalitis is frequently devastating
• All patients with a febrile illness and altered behaviour or
consciousness should be investigated promptly for viral encephalitis
• Patients suspected need a lumbar puncture as soon as possible
• Early institution of therapy improves prognosis
37. References
• Ftichard T. Johnson, Acute Encephalitis, Clinical Infectious Diseases
1996;23:219-26
• WHO – recommended standards for surveillance of selected vaccine-preventable
diseases. Geneva: WHO; 2006: http://www.who.int/vaccines-
documents/DocsPDF06/843.pdf
• DiseaseM.Saminathan, K. Karuppanasamy, S. Pavulraj, A. Gopalakrishnan and R.
B. Rai Acute Encephalitis Syndrome - A Complex Zoonotic Int. J. Livest. Res.
2013; 3(2): 174-177
• Tom Solomon, Ian J Hart, Nicholas J Beeching; Viral encephalitis: a clinician’s
guide; Practical Neurology 2007;7;288-305
• Allan R. Tunkel et al, The Management of Encephalitis: Clinical Practice
Guidelines by the Infectious Diseases Society of America; Clinical Infectious
Diseases 2008; 47:303–27
• David Schlossberg, Clinical Infectious Disease 2nd Edition; 2015 Chapter 76
38. References
• Dennis L. Kasper et al, Harrison’s Principles of Internal Medicine, 19th
Edition; 2015, p. 893-898
• Venkatesan et al, Case Definitions, Diagnostic Algorithms, and Priorities in
Encephalitis: Consensus Statement of the International Encephalitis
Consortium; Clinical Infectious Diseases 2013;57(8):1114–28
• Sergio Ferrari et al, Viral Encephalitis: Etiology, Clinical Features,
Diagnosis and Management, The Open Infectious Diseases Journal, 2009, 3,
1-12
• Richard J. Whitley, Herpes Simplex Virus Infections of the Central Nervous
System, Continuum (Minneap Minn) 2015;21(6):1704–1713
• T. Solomon et al, Management of suspected viral encephalitis in adults-
Association of British Neurologists and British Infection Association
National Guidelines; Journal of Infection (2012) 64, 347e373