Page 633 - Concise Pathology for Exam Preparation ( PDFDrive )

618 SECTION II Diseases of Organ Systems

Q. Write briefly on viral encephalitis.

Ans. Viral encephalitis is a viral infection of the brain parenchyma, which is invariably
associated with meningeal inflammation.

Characteristic histological features:
• Perivascular and parenchymal mononuclear cell infiltrate

• Multiple foci of necrosis; in particular, single cell necrosis with phagocytosis of the debris

(neuronophagia)
• Formation of glial nodules (due to glial proliferation)
Diagnosis:
• Direct evidence: Presence of inclusion bodies or demonstration of organism
• Indirect evidence: Occurrence of congenital malformations (due to intrauterine viral
infections) and postencephalitis Parkinsonism
Types:
Arthropod
1. borne viral encephalitis:
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Geographic distribution:
• Eastern and Western equine, Venezuelan and St. Louis encephalitis (seen in Western

hemisphere)
• Japanese B encephalitis (seen in Far East)

• Tick-borne encephalitis (seen in Russian and Eastern European regions)
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Clinical presentation:

• Generalized neurological deficit
• Seizures
• Confusion and/or delusions
• Stupor and coma
Pathology:
• Colourless CSF with increased pressure
• Initially, neutrophilic pleocytosis followed by lymphocytosis
• Increased CSF protein
• Normal CSF sugar
Herpes
2. simplex virus-1-associated viral encephalitis
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Salient features:
• Affects children and young adults
• Ten percent patients have history of prior herpes labialis
• Causes encephalitis with mainly temporal lobe involvement
Pathology:
• Necrosis and haemorrhage
• Perivascular inflammation
• Cowdry Type A intranuclear viral inclusions found in both neurons and glia
3 . simplex virus-2 (HSV-2) herpes genitalis–associated viral encephalitis
Herpes
r
o
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• Causes viral meningitis and encephalitis
• Seen in 50% neonates born by vaginal delivery to women with active primary HSV
infection
4. � zoster–associated viral encephalitis
Varicella

Causes granulomatous arteritis and acute encephalitis
5 .
Cytomegalovirus (CMV) associated viral encephalitis: Two patient populations
affected:
• Fetal: Severe periventricular necrosis, brain damage, microcephaly and periventricu-
lar calcification
• Immunosuppressed adults: Subacute encephalitis
Rabies-associated
6. � viral encephalitis

Salient features:
• Transmitted by the bite of a rabid animal usually a dog
• Virus enters CNS from the wound site via peripheral nerves
• Incubation period: 1–3 months
• Nonspecific symptoms like malaise, headache and fever

• Paraesthesias around wound, extraordinary CNS excitability, violent motor responses

(convulsions), contracture of pharyngeal muscles, meningismus and flaccid paralysis

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