Measuring the Neurological Benefits of Intermittent Hypoxia Therapy With MRI

Acute intermittent hypoxia (AIH) is an emerging, safe technique for facilitating neural plasticity in individuals with chronic spinal cord injury (SCI), demonstrating significant transient improvements in respiratory function, plantar flexion, locomotor function, and hand dexterity and strength. Although these studies observe some degree of success eliciting plasticity, we lack a framework for systematic optimization of the AIH protocol for individual patients.

Better understanding of what physiological mechanisms drive AIH-induced neural plasticity in humans will directly inform the development of AIH as an effective treatment option in chronic SCI. This study applies magnetic resonance imaging (MRI) to test how AIH influences vascular and neural properties of the brain and spinal cord.

Individuals with SCI and uninjured participants will be recruited to undergo two MRI scan sessions on one day. In between these scan sessions, participants will undergo a single 30-minute session of AIH. In each scan session, functional MRI will assess AIH-induced changes in neural activation patterns during motor tasks (unilateral isometric hand grasping tasks) and vascular reactivity to breath hold tasks (transient hypocapnia to induce vasodilation). Additional structural scans will be acquired to aid in image analysis.

Inclusion criteria

All participants must meet the following inclusion criteria:

• Between the ages of 18-60 years
• Safe to be scanned using MRI
• Able to communicate in English
• Ability to sign informed consent

In addition, the participants recruited with SCI must meet the following criteria:

• History of a traumatic spinal cord injury, inclusive of levels C2-T1
• At least 6 months since onset of spinal cord injury
• Cause of the spinal cord injury was non-progressive
• Ability to complete and comply with information within the informed consent
• Ability to close and open at least one hand without assistance

Exclusion criteria

• MRI contraindications as indicated on MRI safety screening form
• Subjects with pacemakers, cochlear (in the ear) implants, or aneurysm clips or subjects who have worked with metal
• Women who are currently pregnant, nursing, or planning on becoming pregnant
• Individuals with severe claustrophobia
• Subjects unwilling or unable to give written informed consent in English
• Prisoners
• Frequent smokers (greater than 5 cigarettes per day)
• Blood pressure greater than 160/110 or less than 85/55.
• Individuals who report headaches, feeling dizzy or light-headed, or have heart palpitations on the day of the study.
• Diagnosis of any of the following comorbid conditions: congestive heart failure, cardiac arrhythmias, uncontrolled diabetes mellitus, chronic obstructive pulmonary disease, emphysema, severe asthma, previous myocardial infraction or known carotid/intracerebral artery stenosis, presence of active deep venous thrombosis, or cancer.
• Individuals who utilize mechanical ventilation or have a tracheostomy
• Individuals who utilize an intrathecal baclofen pump
• Orthopedic injury affecting upper extremities
• Currently participating in any other hypoxia related study.