Clinical Reasoning: Encephalopathy in a 10-year-old boy

Abstract

A 10-year-old, right-handed boy with a several-day history of fever and upper respiratory symptoms presented with acute onset headache, emesis, progressive mental status change, and right-sided focal seizures. Symptoms developed over approximately 3 hours. There was no history of recent toxic or medication exposures, travel, immunizations, sick contacts, insect bites, or animal exposures. The general review of systems was negative. ### Question for consideration: 1. What is your initial differential diagnosis based on this information? Initial differential diagnosis should include infection (encephalitis or meningitis), inflammation (connective tissue disease/autoimmune disease, primary or secondary vasculitis, antineuronal antibody mediated encephalopathy), demyelination (e.g., acute disseminated encephalomyelitis), a vascular event (ischemic or hemorrhage), and a malignancy such as a glioma or lymphoma. The patient was loaded with phenytoin and treated empirically with acyclovir and antibiotics while further history was obtained. He was the product of a normal pregnancy and term delivery. His developmental history was normal. Two years prior, he had a similar episode of fever and encephalopathy, which was associated with left-sided focal seizures and left hemiparesis. CT at that time demonstrated swelling of the right temporal lobe. He was presumptively diagnosed with herpes encephalitis, and received a full course of acyclovir. CSF herpes simplex virus (HSV) PCR was negative on 2 occasions. At his …