Neurosurgery notes/Infection/Cranial infection/Viruses/Herpes encephalitis

Herpes encephalitis

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Viruses

Cytomegalovirus (CMV)

General

  • The largest herpesvirus. It is commonly found in all body fluids.
  • CMV is the most frequent congenital CNS infection.
    • Intrauterine infections cause congenital malformations such as microcephaly, hydrocephalus, chorioretinitis, and microphthalmia
  • It causes migration disorders during the first or early second trimester.
  • Transmission is transplacental.

Numbers

  • 75% of women have serum CMV antibodies (which are protective),
  • 1% of newborns have CMV detected in the urine, and
  • 10% of these have CNS infection.

Pathology

  • It affects the brain, heart, liver, and spleen.
  • The virus has an affinity for the germinal matrix and causes perivascular necrosis and calcifications.
  • Premature infants may have hepatosplenomegaly, jaundice, thrombocytopenia, chorioretinitis, seizures, mental retardation, optic atrophy, impaired hearing, and hydrocephalus.
  • CMV ventriculitis and encephalitis where ventricular surface is necrotic and discoloured
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Diagnosis

  • Cultures,
  • Immunoglobulin levels,
  • Intracellular (intranuclear and intracytoplasmic) inclusions on biopsy specimens.
      • Owl eye - Cowdry type A intranuclear inclusions are characteristic of CMV, but these are also found with other infections.
      notion image

Radiographs may demonstrate microcephaly and periventricular eggshell calcifications.

Varicella zoster

  • The primary infection is varicella after which the virus becomes latent in the DRG.
  • A reactivation is zoster (shingles) that mainly affects the elderly and immunocompromised.
  • 2/3 of cases are levels T5–T9, and 15% of cases involve CN V1 (trigeminal ophthalmic branch).
  • Pathology
    • Intranuclear inclusions in the DRG and the posterior horn gray matter, posterior roots, and meninges
  • Treatment
    • Skin lotions (calamine), capsaicin,
    • Acyclovir (must be given within 48 hours of rash formation to decrease the duration of disease, use
      • 7-day oral course or
      • 10-day IV course for immunocompromised patients or if >3 dermatomes involved)
    • Topical acyclovir for the eye with a V1 infection.
    • Postherpetic pain is treated (although it responds poorly) with amitriptyline, carbamazepine, gabapentin, pregabalin, and time.