Neuroimaging studies of delirium: a systematic review

OBJECTIVE: Neuroimaging offers clear potential in developing a better understanding of the pathophysiology of delirium. We performed a systematic review of structural and functional neuroimaging findings in delirium. The aims were to categorize and summarize the existing literature, and to determine whether this literature provides conclusive information on structural or functional brain predictors, correlates, or consequences of delirium.

METHODS: Studies were identified by comprehensive textword and MeSH-based electronic searches of MEDLINE, EMBASE, and Evidence-Based Medicine reviews, combining multiple terms for neuroimaging, brain structure, and delirium.

RESULTS: Twelve studies met the inclusion criteria. There were a total of 194 patients with delirium and 570 controls. Patient age, population, comorbidities, and identified precipitating factors were heterogeneous. Of the 10 structural studies, 3 studies used computed tomography (CT), 3 studies used magnetic resonance imaging (MRI), and 4 studies used a mixture of CT and MRI. One functional study used xenon CT, and the other used single photon emission computed tomography. There was a wide range of measurement techniques and timing of scans. Some studies found associations between delirium and cortical atrophy, and between ventricular enlargement and white matter lesion burden, but many studies did not control for potential confounders. Only two small studies of cerebral blood flow were identified, with both suggesting that there may be reduced regional cerebral blood flow, but the data were limited and somewhat inconsistent.

CONCLUSIONS: The small sample sizes and other limitations of the studies identified in this review preclude drawing any clear conclusions regarding neuroimaging findings in delirium, but these studies suggest multiple avenues for future research.