Meningitis Viral and Encephalitis
1.4. Diagnosis
Presence of HSV DNA in CSF detected by PCR is best means to make a diagnosis of
HSV encephalitis. Arboviral infection detected by serum antibody of CSF, culture of CSF
or serum antibody. Enteroviruses can be cultured from CSF, stool, and throat wash.
1.5. Differential Diagnosis
The differential diagnosis requires the exclusion of tumors, vascular malformations, a
fungal or tuberculous process, toxoplasmosis, brain abscess, bacterial meningitis with an
encephalitic component, Lyme disease, syphilis, or lead intoxication.
1.6. Prognosis
In contrast to aseptic meningitis the morbidity and mortality for encephalitis is
considerable. The prognosis depends somewhat on the specific causative agent. For
example, the overall mortality for arboviral encephalitis in the United States between
1955 and 1971 was 50% for Eastern Equine Encephalitis (EEE), 8% for St. Louis
Encephalitis (SLE), 2.9% for Western Equine (WE) and 0.4% California for (CE).
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The mortality for untreated Herpes simplex encephalitis is 70%.With current therapy,
acyclovir, the mortality can be reduced to about 15-20% but there may be considerable
morbidity with long term neurologic sequelae, especially if the onset of treatment is
delayed.
In children with WEE who were < 1 year of age at the onset of infection, 57% developed
either mental retardation, paralysis, seizures, spasticity, speech difficulties, hearing
defects.
The most treatable form of viral encephalitis is Herpes simplex.
There has been the introduction of a new course of viral encephalitis into US from
Middle East-West Nile Encephalitis. It is a flavivious like St. Louis Encephalitis,
Japanese Encephalitis and Dengue. Clinical manifestations similar to other viral
encephalitides except profound weakness, lower motor neuron symptoms common. Most
severe illness in elderly. Expanding pool of virus activity throughout US over 90 deaths
last year.