1485: Herpes Simplex Encephalitis Mimicking a Stroke With Favorable Response to Adjuvant Corticosteroids

Introduction: Herpes simplex virus encephalitis (HSVE) is a life-threatening condition that requires prompt antiviral therapy to reduce mortality and neurological sequelae. Despite the effectiveness of intravenous Acyclovir, a subset of patients may deteriorate due to intense cerebral inflammation, leading to cerebral edema. The role of corticosteroids in such cases remains controversial but may offer therapeutic benefits. Description: A 53-year old woman presented to the emergency department with confusion, slurred speech, and dysphasia following a one-week history of flu-like symptoms. There were no focal neurological deficits on initial examination. The patient had a National Institutes of Health Stroke Scale score of 10. Non-contrast Computed tomography (CT) of the head suggested an acute or subacute infarct in the right middle cerebral artery territory, with an M1 segment thrombus. CT angiography showed no persistent large vessel occlusion she was managed initially as ischemic stroke. Further evaluation with brain MRI revealed swelling and leptomeningeal enhancement of the right temporal lobe, raising suspicion for HSVE. Lumbar puncture was performed, and empirical acyclovir along with broad-spectrum antibiotics was initiated. Despite treatment, the patient’s condition deteriorated over 48 hours. Repeat CT revealed diffuse cerebral edema involving the right temporal and frontal lobes, with subfalcine herniation and a 5.9 mm midline shift. Cerebrospinal fluid analysis revealed pleocytosis, elevated protein, and was positive for HSV-1 PCR, confirming HSVE. Antibiotics were discontinued, and intravenous dexamethasone and hypertonic saline were initiated to manage cerebral edema. By day five the patient exhibited marked clinical improvement despite this, her recovery was complicated by residual cognitive deficits and a prolonged course of rehabilitation. Discussion: This case underscores the diagnostic challenges in HSVE, particularly when it presents with stroke-like features. The initial misdiagnosis of ischemic stroke delayed the initiation of antiviral therapy and the development of cerebral edema. The subsequent use of corticosteroids and hypertonic saline therapy was associated with rapid clinical improvement, suggesting a beneficial role in managing HSVE-related inflammation and edema.