Brain Network Dysfunction in Poststroke Delirium and Spatial Neglect: An fMRI Study

Abstract

Background and Purpose: Delirium, an acute reduction in cognitive functioning, hinders stroke recovery and contributes to cognitive decline. Right-hemisphere stroke is linked with higher delirium incidence, likely, due to the prevalence of spatial neglect (SN), a right-brain disorder of spatial processing. This study tested if symptoms of delirium and SN after right-hemisphere stroke are associated with abnormal function of the right-dominant neural networks specialized for maintaining attention, orientation, and arousal. Methods: Twenty-nine participants with right-hemisphere ischemic stroke undergoing acute rehabilitation completed delirium and SN assessments and functional neuroimaging scans. Whole-brain functional connectivity of 4 right-hemisphere seed regions in the cortical-subcortical arousal and attention networks was assessed for its relationship to validated SN and delirium severity measures. Results: Of 29 patients, 6 (21%) met the diagnostic criteria for delirium and 16 (55%) for SN. Decreased connectivity of the right basal forebrain to brain stem and basal ganglia predicted more severe SN. Increased connectivity of the arousal and attention network regions with the parietal, frontal, and temporal structures in the unaffected hemisphere was also found in more severe delirium and SN. Conclusions: Delirium and SN are associated with decreased arousal network activity and an imbalance of cortico-subcortical hemispheric connectivity. Better understanding of neural correlates of poststroke delirium and SN will lead to improved neuroscience-based treatment development for these disorders.

Association of delirium and spatial neglect in patients with right‐hemisphere stroke

“…Maldonado 42 identified breakdown of brain network connectivity as one of the major underlying causes of delirium. For example, the central nervous system's arousal network, which supports arousal and attention and maintains consciousness, 43,44 likely plays an important role in both disorders 45 . Wakefulness and level of consciousness deficits are well documented in delirium and are also common in spatial neglect 46–48 .…”

Unilateral Spatial Neglect Recovery Poststroke

“…Likewise, another fMRI study in patients with right hemisphere stroke found that severity of USN was associated with decreased connectivity of right basal forebrain to brain stem and basal ganglia, as well as increased connectivity within left frontal, temporal, and parietal arousal and attention network regions. 15 Therefore, here we focus on recovery of USN after right hemisphere stroke, consistent with most of the literature on recovery and rehabilitation of USN.…”

“…34 Most studies at that time were relatively small but showed that recovery of USN was associated with increased blood flow in left frontal cortex as well as right parietal cortex 35 or increased glucose metabolism in unaffected areas in both hemispheres. 36 Early activation studies using H 2 15 O positron emission tomography showed that recovery of USN was associated with increased engagement of left frontal eye fields and right superior parietal cortex/precuneus and right parieto-occipital junction, areas previously found to be activated in a spatial exploration task in healthy subjects. 37 Two more recent important studies have used fMRI to evaluate reorganization of neural networks as a mechanism of USN recovery after the first few days following stroke.…”

Regional homogeneity alterations in multifrequency bands in patients with basal ganglia stroke: A resting-state functional magnetic resonance imaging study

“…A study demonstrated that rs-fMRI could be used to assess the functional reorganization of the injured brain in patients with stroke ( Cui et al, 2022 ). Moreover, Boukrina et al (2022) used rs-fMRI to explore the relationship between arousal network activity and delirium after stroke. rs-fMRI has been widely used in the study of stroke.…”