Cerebral Autoregulation, Brain Perfusion, and Neurocognitive Outcomes After Traumatic Brain Injury (CAPCOG-TBI)

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PROJECT SUMMARY Traumatic brain injury (TBI) is a leading cause of disability in adults and the quality of life of TBI survivors is highly dependent on the adequacy of cognitive recovery. TBI is also a risk factor for Alzheimer’s disease (AD) and AD-related dementias (ADRD). Mounting evidence indicates that cerebrovascular dysfunction occurs in both TBI and AD/ADRD and can be a cross-link between the two diseases. The 2019 ADRD Summit called for further studies to understand vascular contributions to progressive cognitive impairment/dementia associated with TBI and develop non-invasive diagnostic approaches5,9. The following important knowledge gaps exist: 1) What is the impact of early cerebrovascular dysfunction after TBI on short and long-term cognitive outcomes after accounting for age, sex, and pre-existing health conditions? 2) What is the temporal relationship between the cerebrovascular function recovery and cognitive outcome after TBI? and 3) Is there a relationship between cerebrovascular dysfunction and post-TBI neurodegeneration? The overarching goal of this proposal is to determine whether acute cerebrovascular dysfunction and its recovery within the first year postinjury are associated with cognitive outcomes and neurodegeneration 12 months after moderate to severe TBI (msTBI). Our central hypothesis is that cerebrovascular function measured by dynamic cerebral autoregulation (CA) and brain perfusion during acute stage and its recovery during the first year are inversely associated with cognitive outcomes and brain volume loss at 12 months postinjury. We propose a longitudinal study with 100 adults who sustained a single msTBI and 30 controls with non-TBI orthopedic trauma in the first week after the initial injury. We will follow them at 3 months, 6 months, and 12 months after injury. The primary outcome will be the NIH Toolbox Cognitive battery fluid composite score supplemented with sensitive episodic memory and processing speed measures at 12 months postinjury. To address the overarching goal, we aim to 1) determine the association of cerebrovascular dysfunction during the acute stage of msTBI (<1-week postinjury) with cognitive outcome at 1 year. CA will be quantified by dynamic changes in arterial blood pressure and cerebral blood flow velocity or brain tissue oxygenation. Brain perfusion will be determined by the sum of cerebral blood flow measured from the bilateral internal carotid artery and vertebral artery. 2) To determine the temporal association between the recovery of cerebrovascular function and cognitive outcomes after TBI. CA and brain perfusion will be measured at 3, 6 and 12 months postinjury. 3) To determine the temporal associations of acute cerebrovascular dysfunction and its recovery with the imaging biomarkers of neurodegeneration after TBI over time. Multimodal MRI studies will be performed at 3 months and 12 months postinjury. The findings from this study will improve our understanding of cerebrovascular contributions to cognitive outcome and neurodegeneration after TBI. The knowledge obtained will provide critical data to inform the development of strategies based on vascular mechanisms to improve cognition and slow neurodegeneration after TBI.