A 53-year-old man was admitted to the emergency department after being found in his home with head injury, reduced alertness, and left hemiplegia. He was last seen well 2 days before. Neurological status was significant for Glasgow Coma Scale 13, left hemiplegia, dysarthria, ataxia, nausea, and vomiting. An unenhanced brain computed tomography (CT) scan found bilateral cerebellar hypodensities compatible with subacute infarcts. A CT angiography of neck and intracranial vessels (Figure, A) showed a linear filling defect in the basilar artery extending the basilar apex with patent bilateral posterior cerebral arteries. The magnetic resonance imaging study confirmed this finding (Figure, B). The patient immediately underwent a digital subtraction angiography (Figure, C), which showed in detail the double lumen of the basilar artery on the longitudinal axis with the confirmation that the main branches of the basilar artery originate from the false lumen (Video). Meanwhile, the right posterior cerebral artery, patent on CT angiography, was occluded. The treatment was conservative (single antiplatelet regimen), and the clinical evolution of the patient was characterized by the appearance of new ischemic lesions in the area of pontine perforating arteries and superior cerebellar arteries and by hemorrhagic transformation of cerebellar ischemia complicated by obstructive hydrocephalus, which required temporary external ventricular drainage. In the short-term neuroimaging follow-up before a fatal outcome, a dilatative or aneurysmatic evolution did not occur.