Discriminant Performance of Dysexecutive and Frontal Release Signs for Delirium in Patients with High Dementia Prevalence: Implications for Neural Network Impairment

Background Prevalence of signs of abnormal executive function (EF) and primitive reflexes (PR) with delirium in older hospitalized patients with or without comorbid dementia has not been reported. Objective To describe prevalence of signs of EF deficits and PR in older inpatients and their discriminant value for delirium while accounting for dementia. Methods Participants were evaluated for delirium using the Diagnostic and Statistical Manual of Mental Disorders 5th edition and the Delirium Rating Scale Revised-98, dementia using Informant Questionnaire on Cognitive Decline in the Elderly, and signs of PR (n = 5) and EF deficits (n = 3) using bedside neuropsychiatric examination. Three indices (PR, EF, and Combined) and 4 diagnostic groups were created for correlational and discriminant analyses. Results Correlations of indices were higher with the Delirium Rating Scale Revised-98 than with the Informant Questionnaire on Cognitive Decline in the Elderly and even higher in those with dementia, especially the Combined index (Delirium Frontal Index). Among individual signs, glabellar and Simple Luria Hand Sequence were most common in delirium and the best for delirium discrimination irrespective of dementia status. The Combined index had about 80% sensitivity and specificity at the ≥2 cutoff in the whole cohort (positive and negative predictive values and likelihood ratios: PPV 50.0%, NPV 93.8%, +LR 3.82, −LR 0.25). The Combined index also had the best performance on discriminating delirium in dementia patients at the ≥3 cutoff, with about 80% for both sensitivity and specificity. Conclusions PR and EF deficit signs are consistent with reduced neural network integration during delirium, even worse in those with dementia whose baseline structural injury impairs network connectivity with frontal regions. We recommend simple bedside assessment of PR and EF signs to help assess for delirium as an indicator of cerebral cortical neural network impairment in older persons.