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HSV Encephalitis MRI — SCE Infectious Diseases MCQ

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EasyCNS InfectionHSV Encephalitis MRISCE Infectious Diseases

A 35-year-old man presents with acute-onset severe headache, neck stiffness, and photophobia. CSF shows: WCC 520/µL (60% lymphocytes, 40% neutrophils), protein 1.8 g/L, glucose 2.5 mmol/L (serum 5.2). Gram stain is negative. He recently had a cold sore on his lip. CSF HSV PCR is positive. What is the expected MRI finding?

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Correct answer: A — Temporal lobe hyperintensity (characteristically asymmetric) on T2/FLAIR sequences

HSV encephalitis characteristically affects the temporal lobes (due to viral tropism for the limbic system via the olfactory and trigeminal nerves). MRI shows asymmetric T2/FLAIR hyperintensity in the medial temporal lobes, insular cortex, and orbitofrontal regions, often with haemorrhagic components. Diffusion-weighted imaging (DWI) may show early restriction. MRI is more sensitive than CT for detecting these changes. The temporal lobe predilection is highly characteristic and helps distinguish HSV from other viral encephalitides.

Reference: NICE CG102 2010 – Encephalitis; RCR 2024 – Neuroimaging in encephalitis