Neuro

Herpes Simplex Encephalitis

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Pathology

Herpes Simplex Virus (HSV) is a DNA virus. 
Pathologically characterized by a necrotizing microencephalitis associated with oedema, haemorrhage, and encephalomalacia

Aetiology

HSV-1 is associated with orofacial infection
HSV-2 is associated with genital infections. 
Herpes simplex encephalitis should be strongly suspected when there are focal features clinically or radiologically suggestive of temporal lobe or orbitofrontal cortex involvement. 

Signs

Seizures, focal deficits such as dysphasia, hemiparesis, visual field defects, loss of sense of smell.

Symptoms

Headache, fever, personality changes, alteration of consciousness

Investigations

Imaging: MRI brain - Temporal/orbitofrontal lobe high signal changes
Lumbar Puncture: Lymphocytosis with elevated protein and normal glucose
Viral PCR for HSV is usually positive
EEG: Focal changes in temporofrontal areas

Treatment

Medical IV acyclovir for 14-21 days, antiepileptic drugs may be required.

Prognosis

Early suspicion and commencement of antiviral therapy is vital for good prognosis. If untreated, mortality can be as high as 70%. Complete recovery is only seen in a very small percentage of patients (2.5%). 
Long term neurological sequelae such as cognitive impairment and seizures

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Key References

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