Extratemporal herpes encephalitis during natalizumab treatment: A case report.

Herpes simplex virus encephalitis (HSE) is a rare but often fatal disease if left untreated. MRI typically shows the characteristic findings of medial temporal lobe and insular involvement, while diagnosis in confirmed by CSF PCR. In immunocompromised state, HSE may have atypical clinical and radiological features. We report a MS patient under natalizumab treatment with HSE, who presented with MRI lesions exclusively in the right parietal lobe. The patient was timely started on acyclovir resulting in marked improvement. A high index of suspicion for HSE should be maintained when a patient presents with fever and extratemporal lesions, even more in immunocompromised subjects.