The risk of sustaining Traumatic Brain Injury (TBI) and co-morbid post traumatic dizziness is elevated in military operational environments. Sleep deprivation is known to affect Service Member performance while deployed though little is known about its effects on vestibular function. Recent findings suggest that moderate acceleration step rotational stimuli may elicit a heightened angular vestibulo-ocular reflex (aVOR) response relative to low frequency sinusoidal stimuli after 26 hours of sleep deprivation. There is concern that a sleep deprivation-mediated elevation in aVOR function could confound detection of co-morbid vestibular pathology in Service Members with TBI. Dynamic Visual Acuity (DVA) refers to one's ability to see clearly during head movement and is a behavioral measure of aVOR function. The Dynamic Visual Acuity Test (DVAT) assesses gaze instability by measuring the difference between head-stationary and head-moving visual acuity.
The purpose of this study was to investigate the effects of 26 hours of sleep deprivation on DVA as a surrogate for aVOR function.
20 Soldiers with no history of vestibular insult or head trauma were assessed using the DVAT at angular head velocities of 120-180 degrees/ second. Active and passive yaw and pitch impulses were obtained before and after sleep deprivation.
Yaw DVA remained unchanged due to sleep deprivation. Active pitch DVA diminished by -0.005 LogMAR (down) and -0.055 LogMAR (up); and passive pitch DVA was degraded by -0.06 LogMAR (down) and -0.045 LogMAR (up) (p=0.002).
DVA testing in healthy soldiers revealed no change in gaze stability following rapid yaw impulses and sub-clinical changes in pitch DVA following sleep deprivation. Findings suggest that DVA is not affected by short term sleep deprivation under clinical conditions.
Source: http://ptjournal.apta.org/cgi/content/short/ptj.20120144v1?rss=1
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