RESUMEN
Occipital lobe infarction secondary to tentorial herniation is a rare but well-recognized complication of posterior cerebral artery interruption during acute hydrocephalus; however, a similar event in which tonsillar herniation leads to symptomatic occlusion of the anterior spinal arteries (ASAs) has not been reported. The authors present the case of a third ventricular colloid cyst in a previously healthy 24-year-old man who presented with symptoms and signs of critically raised intracranial pressure. He subsequently survived the ictus of insults following emergency external cerebrospinal fluid drainage and definitive resection of the colloid cyst, but he sustained occipital lobe and spinal cord infarction despite the absence of systematic hypotension. The presence of watershed cervicothoracic cord infarction on magnetic resonance imaging suggested that the most likely causes were compromise of ASAs during the period of acute hydrocephalus and the accompanying downward brain herniation. To the authors' knowledge, this is the first report to provide evidence that acute hydrocephalus may lead to ASA syndrome.