Isolated thrombosis of the vein of Galen is a rare and serious entity with few cases reported in the literature. We report the case of a previously healthy 18-year-old male who was admitted after developing headache and subsequently worsening mental status, requiring endotracheal intubation for airway protection. During his admission he developed symptoms of severe paroxysmal sympathetic hyperactivity and posturing. The computed tomography and magnetic resonance imaging of the brain showed bilateral thalamic lesions. The magnetic resonance angiography and digital arteriography revealed a thrombosis of the deep cerebral venous system (vein of Galen). We call attention to a case with rapid symptom progression and specific radiological findings, with atypical clinical course, characterized by paroxysmal sympathetic hyperactivity, but with good clinical functional outcome.