Herpes Simplex Virus (HSV) is a DNA virus. 

Pathologically characterized by a necrotizing microencephalitis associated with oedema, haemorrhage, and encephalomalacia

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. 

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

Headache, fever, personality changes, alteration of consciousness

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

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%).