PLE-4824

A 3-year-old girl has a 2-week history of fever associated with headache, lethargy, and vomiting. She has a history of perioral cyanosis and dyspnea with exertion ever since she was an infant. She suddenly has a 10-minute tonic-clonic seizure. The child is obtunded afterwards, with a temperature of 38.2C, PR 118/min, BP of 100/70. Perioral cyanosis is noted at rest. A harsh pan-systolic murmur is heard along the left sternal border. Fundoscopy reveals papilledema. She is also noted to have right-sided weakness. What is the most likely cause of her hemiparesis?