Acute encephalitis is an inflammation of the brain that can be caused by a variety of viruses, bacteria, and other pathogens. Common causes include enteroviruses, arboviruses like Japanese encephalitis virus, and herpes viruses. Clinical features depend on the area of brain involved but often include fever, headache, seizures, and altered mental status. Diagnosis involves examination of cerebrospinal fluid and blood tests. Management focuses on supportive care, monitoring for complications, and treating any underlying infection. Prevention strategies target reducing exposure to pathogens like mosquitoes that transmit certain viruses.

1. ACUTE ENCEPHALITIS
DR. P. SOUNDARARAJAN,
PROFESSOR OF PEDIATRICS,
MGMCRI.

2. Terms to understand
• Encephalitis
• Encephalopathy
• Meningitis
• Meningism
• Myelitis

3. Meningoencephalitis
• Acute inflammation of meninges & brain
tissue
• CSF – pleocytosis
• Gram stain & culture negative
• Changes in MRI brain
• Mostly self limiting

4. Etiology
• Enterovirus; coxsackie, polio, echo
• Arbovirus; JEV, WNV, Dengue
• Herpes virus; HSV1&2, VZ, EBV, CMV.
• Others; mumps, measles, rabies, adenoV.
• Bacteria; TB, mycoplasma, rickettsiae
• Protozoa; acanthameba, toxoplasma

6. JEV

7. JEV

8. • Annual incidence : 16/100 000 in children
[4-8 /100 000 in adults]

9. • HSV; 22%
• VZV; 21%
• Adeno V; 4%
• JBE in asia; 35000 – 50000 cases / year.
1/3 die , june to september.

10. JEV
• Flavivirus
• Spread by culex
• Single stranded RNAV
• 1955 in pondicherry; 1st case
• 2005; 1400 deaths in UP & Bihar
• 2014; WB, UP, assam; ~ 300deaths

12. Pathogenesis
• Direct invasion & destruction by virus
• Host reaction to viral antigens
• Meningeal congestion
• Mononuclear infiltration
• Neuronal disruption
• Neuronophagia, vasculitis
• Demyelination [ADEM]

13. Structures affected
• HSV; temporal lobe
• Arbovirus; entire brain
• Rabies; basal parts
• Varicella; cerebellum

14. 4 stages
• 0-3d ; prodrome
• 4-7d; acute
• 8-10d; subacute
• 1-4wk; recovery

15. Clinical features
• Depends on parenchymal involvement
• Preceding mild febrile illness & exantheme
• Acute onset of high fever, headache, irritability,
lethargy, nausea, myalgia
• Convulsions, stupor, coma
• Fluctuating FND, emotional outburst
• Ant.horn cell injuryflaccid paralysis [west nile,
entero virus]

16. Clues in history
• Travel to endemic places

17. Clues in examination
• Cranial N palsy; HSV, EBV, TB.
• Ataxia; VZV,
• AFP; polio, enteroV, tick borne.
• Rash; VZV, typhus, mycoplasma
• Parotitis; mumps,
• LN; HIV, EBV, CMV, Rubella.
• Hydrophobia; rabies.

18. Diagnosis
CSF: lymphocytic predominance
 Protein: normal, high in HSV
 Glucose: normal, low in mumps
 Hemorrhagic; measles
 Viral antigen by PCR
Blood:
 Culture from NP swab, vesicle, feces, urine
 IgM, IgG titre

20. EEG in HSV

24. Bilateral asymmetric
thalamic hyper intensity

25. Substantia nigra involvement

28. Management in ICU

29. Management
• Monitor GCS
• ABC
• Restrict IVF
• Anticovulsants, antipyresis ,
• Treat ICT
• Moitor; glucose, BUN, elect, ABG, LFT,

30. Infant < 1 yr Child 1-4 yrs > 4 years
EYES
4 Open Open Open
3 To voice To voice To voice
2 To pain To pain To pain
1 No response No response No response
VERBAL
5 Coos, babbles Oriented, speaks,
interacts, social
Oriented and Alert
4 Irritable cry,
consolable
Confused speech,
disoriented, consolable
Disoriented
3 Cries persistently to
pain
Inappropriate words,
inconsolable
Nonsensical speech
2 Moans to pain Incomprehensible,
agitated
Moans, unintelligible
1 No response No response No response
MOTOR
6 Normal spontaneous
movement
Normal spontaneous
movement
Follows commands
5 Withdraws to touch Localizes pain Localizes pain
4 Withdraws to pain Withdraws to pain Withdraws to pain
3 Decorticate flexion Decorticate flexion Decorticate flexion
2 Decerebrate extension Decerebrate extension Decerebrate extension
1 No response No response No response

31. Bad Prognosis
• <3 yrs
• GCS <6 for 4days
• Hyponatremia
• 50-60% sequalae

32. Prevention