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| Herpes Encephalitis |
Overview
 | caused by Herpes simplex virus (HSV-1) |
| Two thousand cases occur each year in the United States |
| Adult HSV encephalitis can reflect primary infection, reinfection, or
reactivation of latent agent |
| Can affect any age group, but most common in those under 20 and over 40. |
| Exposure to infected saliva or respiratory secretions, ascend along the
olfactory nerve into the limbic lobe, or from reactivation of virus from Trigeminal
ganglion |
| 90% of patients show evidence of temporal lobe involvement |
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Symptoms
| Fever & headache for several days |
| Followed by behavioral changes, seizures (40%), hemiparesis (33%), and
depressed level of consciousness. |
| Atypical cases include patients without focal features, and patients who
show a slowly progressive course. |
| It has been suggested that up to 20% of HSV encephalitis cases may take
this atypical form. This has led to the recommendation that CSF PCR studies for HSV (both
types 1 and 2) be carried out in any febrile, encephalopathic patient with an unclear
etiology for their syndrome. |
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Tests
| EEG often abnormal:
 | Diffuse slowing or |
| Uni or bilateral temporal periodic discharges or |
| Slow wave complexes at 2-3/second interval. |
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| CT/MRI: abnormal mass lesion at temporal lobe |
| CSF: WBC 50-500, predominantly lymphocytes, elevated protein, normal
glucose |
| May not be able to do Lumbar puncture if there is severe mass effect |
| Brain biopsy: preferably by open biopsy, higher false negative with
Stereotatic biopsy |
| Diagnostic test of choice is CSF PCR
| Sensitivity rates as high as 98-99%. |
| Remain positive at least several days into treatment. |
| Quantitative PCR indicate that higher viral loads in CSF appear to have a
worse prognosis. |
| Intrathecal antibody production takes at least one week to develop, but
can be a useful late confirmatory measure. |
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| CSF
Polymerase chain reaction analysis may be more specific and sensitive - PubMed |
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| Differential diagnosis
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Treatment
| Acyclovir 10mg/kg q8h iv (30mg/kg/day), infuse each dose over 1
hour, treat for 10-14 days |
| May cause transient renal insufficiency, provide adequate hydration |
| Treat seizures with anticonvulsant |
| Treat increased intracranial pressure |
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Prognosis
| untreated: mortality > 70% |
| treated: mortality 19%. 38% return to normal function |
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| Further Reading
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Neuro infection info center
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