This document discusses viral encephalitis, including its epidemiology, causes, pathogenesis, clinical features, diagnosis, and treatment. It notes that viral encephalitis accounts for about 70% of encephalitis cases. Common causes include herpes simplex virus, West Nile virus, Japanese encephalitis virus, and mosquito-borne viruses. Viruses generally spread to the brain via bloodstream and can transmit neuronally. Clinical features include headaches, fever, altered mental status, seizures, and meningismus signs. Diagnosis involves neuroimaging, lumbar puncture for CSF analysis, and PCR testing of CSF. Treatment depends on the underlying cause but may include antivirals for HSV or acyclovir for

2. Introduction
• Conditions involving inflammation of the brain Parenchyma
• It can be due to variety of causes
Epidemiology and risk Factors
• Incidence of viral Encephalitis is ~3.5 – 7.5 per 100,000
• Highest incidence in young and elderly populations
• Increased risk in those immune compromised
• HIV positive, Organ transplant patients
• Exposure to infective vectors in endemic areas (eg: Bats)

3. Causes
• Viruses –( viral encephalitis)
• Most Commonly caused by viral infection
• Accounts for approximately 70% of cases
• Herpes Simplex virus (“Herpes Simplex Encephalitis”)
• West Nile Virus
• Mosquito – borne viruses : Dengue Virus, Equine viruses, St. Louis virus, Zika virus, Japanese
Encephalitis Virus
• Other less common Viral Causes : EV71, Polio virus, Epstein-Barr Virus (EBV),
Cytomegalovirus(CMV), Measles virus, Mumps Virus, Rubella Virus, Rabies virus, Herpes zoster
Virus
• Toxoplasmosis – protozoan
• Cerebral aspergillosis
• T-cell Lymphoma
• Metabolic Encephalopathies
• Anti-NMDA receptor encephalitis (“Brain on Fire”)

4. Pathogenesis
• Hematogenous Spread
• Most viral agents spread
to the central nervous
system via hematogenous
spread i.e. Via Blood
stream
• Neuronal Transmission
• Viral agents transmit via
neuronal transmission
• HSV, Herpes zoster,
Rabies Virus
• HSV resides within
neurons and may
undergo retrograde
transmission
Viruses invade brain tissue, and along with the host inflammatory response, neuronal
activity becomes disrupted or intruded

5. Clinical Features
• Prodrome_ Headaches, Myalgias, Malaise
• Onset of worsening symptoms over hours to days
• Fever
• Altered Mental status
• Seizures, Coma
• Focal Neurological Deficits

6. Other features
• Meningitis signs and symptoms..,
• Nuchal rigidity (“neck stiffness”)
• Brudzinski’s sign
• Kernig’s sign
• Nausea and vomiting
• Photophobia and phonophobia

7. Associated symptoms
• HSV Encephalitis
• May have Previous History of cold sores
• May have memory issues, and/or aphasia
• EBV Encephalitis
• Lymphadenopathy and splenomegaly
• Japanese Encephalitis Virus
• Parkinsonian features
• May mimic Parkinson’s Disease
• Asymmetric Lower limb paralysis
• EV71 Encephalitis
• May cause pulmonary oedema, tremor, Myoclonus
• Anti NMDA receptor Encephalitis
• Symptoms of underlying cancer (ovarian teratoma)

8. Diagnosis
• Clinical diagnosis of underlying causes is extremely
difficult
• Neuroimaging and lumbar puncture(LP)
• CT scan, MRI of Brain
• Low-density lesions within the temporal lobes (may
indicate HSV encephalitis)
• PCR analysis ( for HSV-1 and HSV-2)
• CSF analysis- Normal glucose, elevated proteins,
Moderate Lymphocytosis
• Assess opening pressure on LP
• EEG for the assessment of Japanese Encephalitis
Virus

9. Treatment
• Depend on underlying aetiology
• Most have no specific treatment, but we can treat the symptomatically
• If seizing - Levetiracetam 15-60mg/kg/day
• Lorazepam 0.1mg/kg
• Diazepam 0.15-0.25mg/kg
• Midazolam 0.2mg/kg>>0.05-0.4mg/kg/hr
• HSV Encephalitis, Varicella Zoster Virus Encephalitis – Acyclovir 200-400mg
every 4 hr
• CMV Encephalitis – Ganciclovir 5mg/kg/day q12hr and foscarmet 60mg/kg
q8hr
• Immunocompromised patients
• Steroids prednisolone 20mg/kg
• Increased ICP on serial measurements associated with poor prognosis
• ?Steroids and Mannitol
Supportive treatment like treating Reversible causes.

10. Thank you