Adult presentation of a vein of Galen malformation as cognitive decline in a 47-year-old multiparous female: illustrative case.

backgroundVein of Galen malformations (VOGMs) are congenital arteriovenous shunts that typically present in neonates and infants. Symptomatic neonates have a poor prognosis and face high mortality without dedicated neonatal intensive care and pediatric neurointervention in specialized centers. OBSERVATIONS: The authors present the case of a 47-year-old Puerto Rican female with a history of chronically compensated heart failure, progressive cognitive decline, and new-onset seizures. On presentation, the patient had a Glasgow Coma Scale score of 6, and CT imaging revealed intraventricular hemorrhage, extensive parenchymal calcifications, and hydrocephalus. An external ventricular drain was urgently placed, and further workup at the authors' institution, including CT angiography and digital subtraction angiography, led to the diagnosis of a choroidal VOGM. The patient's family opted for withdrawal of care without pursuing further neurosurgical intervention. LESSONS: The presentation of a choroidal VOGM at this advanced age is exceptionally rare. This case highlights the importance of understanding the presentations and consequences of this life-threatening condition, as well as considering endovascular or microsurgical intervention. Specifically, workup for cerebrovascular abnormalities should be strongly considered in patients with neurodegenerative presentations at atypical ages without a clear cause, as early diagnosis and management can significantly impact patient outcomes. https://thejns.org/doi/10.3171/CASE25684.