Reduced vestibular function in veterans is associated with worse cerebral autoregulation (1068.15)

Recent data has demonstrated that veterans returning from Iraq and Afghanistan have increased incidence of mild traumatic brain injury (mTBI) as well as impaired vestibular function. The objective of this work is to determine if reduced vestibular function is associated with impaired cerebral autoregulation. To asses vestibular function we measured ocular torsion, rotation of the eye within the socket during roll tilt. This vestibular ocular reflex provides us an index of otolith function. To assess cerebral autoregulation we had veterans perform three sit to stand maneuvers while measuring beat‐by‐beat blood pressure, cerebral flow velocity in the middle (MCA) and anterior cerebral artery (ACA) and end tidal CO 2 . 11 Veterans completed both vestibular and cerebral autoregulation assessments. Ocular torsion ranged from 0.03 to 0.32 deg torsion per deg head tilt (Mean 0.14). Ocular torsion was correlated to autoregulatory index (ARI) in the MCA (R 2 =0.115, P=0.058) and the ACA (R 2 =0.212, P=0.018), with lower ocular torsion having reduced ARI. Defining low ocular torsion using a mean split, we found significantly lower ARI values in both MCA (Low 3.4±0.3 vs High 4.7±0.5, P=0.014) and ACA (3.3±0.3 vs 5.0±0.5, P=0.003). These data suggest that impaired vestibular function in these veterans is associated with worse cerebral autoregulation. One possible explanation is that veterans with reduced torsion also have mTBI and thus both the reduced vestibular function and the impaired autoregulation are a consequence of mTBI. Further work is needed to examine the connection between mTBI, vestibular function and cerebral autoregulation. Grant Funding Source : Supported by Dept of Veteran Affairs and NIH R21 DC009900