Malignant cerebral edema secondary to herpes simplex virus encephalitis requiring decompressive hemicraniectomy.

Herpes simplex encephalitis (HSE) is a severe viral infection of the central nervous system that most commonly affects the temporal lobes and limbic structures. Although most cases are managed medically with intravenous acyclovir, rare cases can rapidly progress to malignant cerebral edema, mass effect, and neurologic deterioration requiring surgical intervention. We report the case of a 57-year-old woman presenting with altered mental status, headache, vomiting, myalgias, and focal neurologic deficits. Initial computed tomography (CT) and CT angiography of the head and neck were unremarkable, but magnetic resonance imaging (MRI) demonstrated diffusion restriction involving the right mesial temporal lobe and insular cortex. Cerebrospinal fluid testing later confirmed HSE. Despite treatment with intravenous acyclovir, the patient developed worsening right hemispheric edema with progressive midline shift, requiring external ventricular drain placement followed by emergent right decompressive hemicraniectomy. She subsequently improved without persistent focal neurologic deficits and later underwent cranioplasty. Our case highlights the importance of early recognition with neuroimaging, close neurologic monitoring, repeat imaging, and timely neurosurgical intervention in severe herpes simplex encephalitis complicated by malignant cerebral edema.