Herpesvirus

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  • i. Herpesviruses include herpes simplex virus type 1 and 2, EBV, and CMV
  • ii. Herpes simplex encephalitis
    • 1. commonest form of acute necrotizing encephalitis
    • 2. causes congestion and hemorrhagic necrosis of the temporal lobes and/or frontal cortex
    • 3. spread by direct contact with infected secretions
    • 4. may enter brain through olfactory bulbs but etiology is uncertain
    • 5. microscopically see scanty parenchymal inflammation with moderate numbers of lymphocytes and macrophages overlying the meninges
      • a. affected neurons, glia, and endothelial cells tend to have eosinophlic cytoplasm with inclusions
  • iii. neonatal herpes encephalitis
    • 1. mostly due to HSV-2; acquired during delivery from contact between the fetus and infected maternal genital lesions
    • 2. treat with acyclovir which reduces mortality to 15% and allows 50% to develop normally
    • 3. similar histologic pattern as adults
  • iv. herpes zoster
    • 1. due to upper respiratory infection with secondary activation causing shingles after living in the dorsal root ganglia of spinal or cranial nerves; same agent that causes chicken pox
    • 2. Cowdry type A inclusions are NOT present in herpes zoster
    • 3. may cause transient meningitis but rarely is it symptomatic
    • 4. herpes zoster has not been associated with serologic evidence of activation in Bell’s palsy, trigeminal neuralgia and intercostals neuralgia but Bell’s palsy has been associated with herpes simplex virus
      • a. pain and herpetic eruption due to herpes zoster infection of the Gasserian ganglion and the peripheral and central pathways of the trigeminal nerve are practically always limited to the first division with eruption 4-5 days after the onset of pain; treatment: vidarabine and acyclovir but pain may become intractable – in these patients add antidepressant such as amitriptyline or fluoxetine; rhizotomy should be avoided since they usually result in diffuse refractory dysesthesia
      • b. herpes zoster involvement of CN 5 most commonly affects CN 4 because it shares its nerve sheath with the ophthalmic division of the trigmeninal nerve
    • 5. Ramsay Hunt syndrome is an eruption of herpes virus in the external auditory canal along with a facial palsy due to herpes infection
      • a. Other herpes zoster associations: encephalitis causing acute cerebellar ataxia, aseptic meningitis, polyneuritis
  • v. CMV
    • 1. may cause a low grade encephalitis with CMV inclusion cells with ventricular dilation, seizures, chorioretinitis, optic atrophy, microcephaly and periventriuclar calcification
    • 2. CMV is also associated with ascending polyradiculopathy with sensorimotor involvement with early onset of bowel and bladder impairment
    • 3. treatment : ganciclovir or foscarnet; ganciclovir is effective at treating the retinitis of CMV infection
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