This study investigated whether adult-onset hydrocephalus is associated with an increased risk of incident epilepsy. 4ConclusionThese findings suggest that adult-onset hydrocephalus is associated with an increased risk of epilepsy that is not fully explained by vascular risk factors, neurodegenerative comorbidities, or shunt-related complications. Evidence on the relationship between adult-onset hydrocephalus and epilepsy is limited, particularly in adults without secondary causes of hydrocephalus. RELEVANCE TO EUROPEAN PRACTICEThese findings may be relevant to clinicians involved in the care of people with adult-onset hydrocephalus. Prospective studies are needed to confirm these findings and to investigate the biological mechanisms linking adult-onset hydrocephalus and epilepsy.