Persistence of Grandiose Delusional Content in Schizophrenia with Superimposed Vascular Dementia: A Case Report of Diagnostic and Therapeutic Impasse

Abstract

Background. Patients with schizophrenia are surviving into old age in growing numbers and are at substantially elevated risk of dementia. When the two conditions coexist, clinicians face contradictory guidance: antipsychotics remain first-line for schizophrenia while carrying a mortality warning in dementia. Evidence to arbitrate between these positions is absent. Case presentation. A 74-year-old man with paranoid schizophrenia of 49 years’ duration presented with agitation and confusion following two years of progressive functional decline. Cognitive assessment yielded a Mini-Mental State Examination score of 14/30, with disproportionate loss of orientation (2/10) relative to recall (2/3). Cranial computed tomography demonstrated severe diffuse cortical atrophy with ventriculomegaly, extensive lacunar infarcts in the bilateral basal ganglia and deep white matter, and confluent periventricular and subcortical leukoaraiosis, in the context of poorly controlled hypertension, dyslipidaemia and smoking. Reversible causes were excluded. Notably, the grandiose delusional system present since the age of 25 persisted unchanged in theme, register and conviction. The patient had received trihexyphenidyl 6 mg/day continuously for decades and risperidone 6 mg/day, neither of which was reviewed. He remains permanently institutionalised. Conclusions. The thematic continuity of the delusional content across five decades distinguishes persisting primary psychosis from psychosis arising within dementia, and has direct therapeutic consequences: deprescribing algorithms developed for behavioural and psychological symptoms of dementia do not apply. Conversely, the case illustrates how an anticholinergic prescribed decades earlier for drug-induced parkinsonism may persist unexamined into a period when the parkinsonian syndrome is more plausibly vascular, at measurable cognitive cost. Systematic cognitive baselines in severe mental illness, executivesensitive screening instruments, and periodic anticholinergic review are proposed.