mTBI, more commonly known as concussion, is well reported in both civilian and military literature, but has gained significant public attention due to the interest of sports related head trauma. The American Academy of Neurology has published (April, 2013) an updated position statement on this increasingly common form of head impact regarding its guidelines and recommendations.

It is recognized that concussion may occur in two classes, cortical (central) and labyrinthine (peripheral), as reported by Scherer et al., 2011. It is vitally important therefore to evaluate both conditions when examining all patients including; soldiers with poly-trauma, student athletes and the elderly who have suffered head trauma secondary to a fall.  Although tests such as the Impact and BESS, have value, they lack the diagnostic efficiency and sensitivity to differentiate between the two classes of mTBI dysfunction. The need for differentiation is critical when determining intervention strategies and ultimately patient readiness to return to play, work or active duty.

Oscillopsia (blurred vision with head movement) is often a cardinal indicator of a non-compensated peripheral or labyrinthine insult. Numerous investigators (Roberts and Gans, 2007, Roberts, Gans, Johnson and Chisolm, 2006, Schubert, Herdman and Tusa, 2002) have reported the utilitarian basis for use of tests of dynamic visual acuity (DVA) both as a clinical significant diagnostic tool, as well as a highly sensitive outcome measurement post therapy. An undiagnosed or untreated oscillopsia, not only provides an incomplete picture of the patient’s status and best treatment options, and is dangerous. The literature indicates a Vestibular Ocular Reflex (VOR) miscue of only 3 degrees may result in vision degrading from 20/20 to 20/200.

In this video you will see AIB staffer, Dr. Darren Kurtzer, as he examines and coaches his patient through a dynamic visual acuity test (AIB CDVAT). Once a static baseline is established the test is performed and scored in horizontal and vertical planes to identify the specific plane of movement  to identify an oscillopsia.  A decrease of 12% or more from static-baseline, for a specific font size and plane of movement is statistically significant. The protocols may also be used for gaze stabilization exercises, and re-test to demonstrate treatment outcome and readiness to return to play. The test developed at AIB in 2000, is based on original NASA research published in 1999 (Hillman et al.), for the space shuttle program. The test is available for purchase on dizzy.com Marketplace. The Roberts and Gans references, below, are available for printing as a PDF from dizzy.com Research and Publications tab.

References:

1. Scherer MR, Burrows H, Pinto R, et al., Evidence of Central and Peripheral Vestibular Pathology in Blast-Related Traumatic Brain Injury, Otology and Neurotology, 32:571-580 (2011)
2. Roberts RA and Gans RE, Comparison of Horizontal and Vertical Dynamic Visual Acuity in Patients with Vestibular Dysfunction and Nonvestibular Dizziness, J Am Acad Audiol 18:236-244 (2007)
3. Roberts RA, Gans RE, Johnson EL, and Chisolm, TH, Computerized Visual Acuity with Volitional Head Movement in Patients With Vestibular Dysfunction, Annals of Otology, Rhinology & Laryngology, 115(9):658-666 (2006)
4. Schubert M, Herdman S, Tusa, R, Vertical Dynamic Visual Acuity in Normal Subjects and Patients with Vestibular Hypofunction, Otol Neurotol, 23:372-377 (2002)