Late-Onset Erotomanic Delusions, Cognitive Impairment, and Ventriculomegaly in an Older Adult Without Prior Psychiatric History: A Neuropsychiatric Case Report

Background: Late-onset psychosis (onset after age 60) in a patient with no prior psychiatric history is uncommon and frequently signals an underlying neurocognitive or structural brain disorder rather than a primary psychiatric illness. Erotomania, the delusional belief that an inaccessible or higher-status person is in love with the patient, has rarely been described together with cognitive impairment and ventriculomegaly. We describe a case in which these three features occurred together and set out the competing explanations for their co-occurrence. Methods: We report a single retrospective case, drawing on inpatient psychiatric and neurology consultation records, cognitive screening with the Montreal Cognitive Assessment (MoCA), head computed tomography, brain magnetic resonance imaging, and one-month outpatient follow-up. Written informed consent for publication was obtained from the patient during the hospitalization, and his capacity for that specific decision was assessed by the treating team. Results: A 75-year-old man with no psychiatric history developed subacute, fixed erotomanic delusions involving a public figure, with an illogical and circumstantial thought process, intermittent disorientation, and severely impaired judgment. Acting on these beliefs, he sold his home and transferred approximately $200,000 to individuals impersonating the celebrity online. Neuroimaging showed ventriculomegaly disproportionate to cortical sulcal prominence together with chronic small-vessel ischemic change. Neurology characterized the picture as borderline or early normal pressure hydrocephalus versus hydrocephalus ex vacuo with a superimposed neurocognitive disorder. The recommended diagnostic large-volume lumbar puncture was not performed, and no quantitative morphometric measurements were obtained, so normal pressure hydrocephalus remained unconfirmed. MoCA performance worsened from 23/30 at admission to 17/30 one month later, although both assessments were obtained during active psychosis and antipsychotic treatment. He was treated with low-dose antipsychotic medication and discharged with outpatient psychiatric and neurosurgical follow-up, and delusions and cognitive impairment persisted at short-term follow-up. Conclusions: New-onset erotomanic delusions in an older adult should prompt evaluation for an underlying neurocognitive or neurological disorder, including structural imaging for potentially reversible causes. This single case cannot establish the direction of the relationship among the erotomanic syndrome, the cognitive impairment, and the ventriculomegaly. Because impaired judgment in this setting can produce catastrophic financial harm, clinicians should pair neuropsychiatric evaluation with formal decisional capacity assessment.