Right Brain Stroke and the Neural Substrate of Delirium

Delirium assessment and prevention has a tremendous impact on hospitalization outcomes and health care costs. Delirium is a multi-component syndrome characterized by an acute reduction in cognitive functioning, affecting awareness, thinking, attention, and memory. Stroke survivors, representing 17% of the US population aged 65 and over (CDC, 2012), are at major risk for developing delirium (up to 50% incidence in right-hemisphere stroke). Further, about 50% of right-hemisphere stroke patients experience spatial neglect, impairing safety and recovery. This study investigates a potential neural mechanism explaining the high incidence of both delirium and spatial neglect after right-hemisphere stroke. The study hypothesis is that the brain networks for arousal and attention, comprised of ascending projections from the mesencephalic reticular formation and integrating right-dominant dorsal and ventral cortical and limbic components, may be affected in these disorders. The study assesses magnetic resonance imaging (MRI) and behavioral data in right hemisphere stroke survivors. It is predicted that impaired activity and structural integrity of the brain networks for arousal and attention will correlate with behavioral signs of delirium and spatial neglect. The study will be conducted at two sites recruiting an acute (n=45) and a subacute (n=30) patient samples. The findings of this study have the potential to impact stroke care by providing a critical biomarker and behavioral profile of post-stroke delirium. This may alert clinicians to initiating preventive care and targeted interventions in patients who are at high risk of hospital morbidity and loss of independence.

Study Hypotheses Hypothesis 1: It is hypothesized that a lesion-deficit analysis will reveal that in patients with delirium and/or spatial neglect, right-brain areas within the attention, orientation, and arousal networks are affected by stroke lesions.

Hypothesis 2: Because it is hypothesized that both disorders stem from a dysfunction of common brain networks, it is expected that spatial neglect severity will be a predictor of delirium severity, controlling for relative lesion size and stroke severity Hypothesis 3: Both spatial neglect and delirium severity will be correlated with functional connectivity among the brain areas within the attention, orientation, and arousal networks.

Hypothesis 4: Based on evidence from prior work in post-surgical delirium patients, neglect and coma patients, it is hypothesized that the integrity of white matter connections among brain regions comprising the cortical and subcortical networks for attention, orientation, and arousal is inversely correlated with the severity of delirium and spatial neglect.

Planned Analyses: