Blood Vessel Anatomy and Blood Flow Regulation

Study Overview
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Brief Summary
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Brain blood flow regulation will be measured in response to environmental changes using MRI.

Detailed Description
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Global brain blood flow decreases with advancing age; however, some adults have accelerated declines in brain blood flow, placing them at a greater risk of cognitive impairment. Similarly, brain reactivity to increased levels of carbon dioxide decreases with age, with a greater decline in adults with vascular risk factors and is impaired in early Alzheimer's disease. Preclinical models suggest that reduced brain blood flow, results in low levels of oxygen regionally. Currently, there are a lack of human studies that investigate the cause or consequence of altered blood flow regulation in the brain. The research aims are: Determine the impact of vertebral artery hypoplasia (VAH) on brain reactivity to increased levels of carbon dioxide. Determine the impact of VAH on the brain blood flow response to acute low levels of oxygen.

Official Title
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The Impact of Cerebral Anatomical Variations on Cerebrovascular Reactivity

Conditions
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Brain Blood Flow, Healthy

Intervention / Treatment
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* Device: MRI


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: BMI ≤38.5 kg/m2 Nonsmoker Female subjects: postmenopausal Currently enrolled in the Wisconsin Alzheimer's Disease Research Clinical Core Exclusion Criteria: Diagnosis of mild cognitive impairment or Alzheimer's disease Uncontrolled hypertension History or evidence of hepatic disease, hematological disease, or peripheral vascular disease Severe kidney injury requiring hemodialysis Cardiovascular disease including: severe congestive heart failure, coronary artery disease, ischemic heart disease (stents, coronary artery bypass grafts) and tachycardia History of clinically significant ischemic or hemorrhagic stroke, or significant cerebrovascular disease History of HIV/AIDS Severe untreated obstructive sleep apnea History of diabetes with HbA1c greater than 9.5% Major neurologic disorders other than dementia (e.g., multiple sclerosis, amyotrophic lateral sclerosis, brain surgery, etc.) Current or recent (<1 year) major psychiatric condition (Axis I) or addictive disorders Contraindications to MRI

Ages Eligible for Study
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Minimum Age: 55 Years
Maximum Age: 69 Years

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Controls<br>Healthy controls | Device: MRI<br>* Participants will undergo an MRI scan while participating in two breathing tests (hypercapnia and hypoxia) to measure brain blood flow.<br>|
| Vertebral Artery Hypoplasia<br>Healthy individuals with vertebral artery hypoplasia | Device: MRI<br>* Participants will undergo an MRI scan while participating in two breathing tests (hypercapnia and hypoxia) to measure brain blood flow.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Cerebral Vascular Reactivity to Hypercapnia | The change in brain blood flow using MRI will be measured in response to a hypercapnic breathing test. The participants cerebral vascular reactivity to hypercapnia will be compared between the controls (without VAH) and those with VAH. | One study visit, up to 120 minutes in the MRI | 
| Cerebral Blood Flow Response to Hypoxia | The change in brain blood flow using MRI will be measured in response to a hypoxic breathing test. The participants cerebral blood flow response to hypoxia will be compared between the controls (without VAH) and those with VAH. | One study visit, up to 120 minutes in the MRI | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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MRI, Brain blood flow