Fever associated with mental confusion, behavioural changes, impaired speech and reduced level of consciousness.
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T2 and FLAIR shows high signal in the left temporal lobe including hippocampal formation and parahippogampal gyrus as well on bilateral insulae gyrus (Involvement is bilateral but asymmetrical). There is slight thickening and meningeal enhancement on left temporal lobe.
Herpes simplex encephalitis is the most common cause of fatal sporadic viral encephalitis and has characteristic imaging findings. Although these abnormalities seen in HSV encephalitis are not unique, more than 90% of patients with proven HSV encephalitis will have magnetic resonance imaging abnormalities involving the temporal lobes.
The patient was transferred from another hospital already being treated with acyclovir. Lumbar puncture shows CSF pleocytosis, but HSV PCR was negative (false negative?).
Negative CSF HSV PCR results should always be interpreted in the context of the timing of specimen collection and the likelihood of disease.
Clinical improvement occurred with treatment.
The diagnosis is presumptive.
- Tyler KL. Update on herpes simplex encephalitis. Rev Neurol Dis. 2006;1 (4): 169-78. Pubmed citation