Cerebrovascular Reactivity in American Football Players

Cerebrovascular Reactivity Assessed With Functional Near-infrared Spectroscopy and Magnetic Resonance Imaging as a Biomarker of Traumatic Microvascular Injury in American Football Players

Investigators will measure cerebrovascular reactivity (CVR) using functional near-infrared spectroscopy (fNIRS) and magnetic resonance imaging (MRI) during the chronic phase after repetitive mild traumatic brain injury (rmTBI) as a biomarker of traumatic cerebrovascular injury (TCVI). We hypothesize that CVR will be decreased in patients with rmTBI and that these decreases will correlate with clinical outcomes. Furthermore, we predict that 5 week administration of a phosphodiesterase 5 (PDE5) inhibitor, sildenafil citrate, will augment CVR in patients with a history rmTBI.

Inclusion Criteria:

1. Age 40-65 years
2. Former National Football League (NFL) players or former varsity college football players
3. Ability to undergo MRI scanning
4. Ability to read, write, and speak English
5. Stable doses of concomitant medications for last 2 weeks prior to enrollment
6. Diagnosis of post-concussive syndrome according to Diagnostic and Statistical Manual 5 (DSM-5) criteria

Exclusion Criteria:

1. Contraindication to sildenafil
2. Past medical history or evidence of penetrating brain injury
3. Daily therapy with a PDE5 inhibitor within the past 2 months, or taken as needed within past 4 weeks
4. History or evidence of pre-existing disabling neurological or psychiatric disorder not related to previous head injuries
5. History of melanoma
6. History of diagnosed obstructive/ restrictive pulmonary disease 7 .) Contraindication to MRI