Research assistant Walter Reed Army Institute of Research
Abstract Text: Military personnel are often exposed to blast overpressure when training with heavy weapons systems. This exposure has been associated with neurotrauma and mild traumatic brain injury (mTBI) symptomology. A concern is that repetitive low-level exposure over a service member’s career may result in long term negative health effects. The military has a standardized tool for concussion assessment, the Military Acute Concussion Evaluation (MACE). Vestibular/Ocular-Motor Screening (VOMS) is a screening tool used to uncover symptoms of an induced brain injury and it is widely used in athletic settings to diagnose head injury. VOMS was appended to the most recent revision of MACE, the MACE2 as updated in 2018. VOMS consists of eight tasks, in which the patient rates four symptoms (headache, dizziness, nausea, fogginess) on 0-10 scale after performing simple physical challenges such as turning their head left and right quickly. It can take approximately 10 minutes to completely administer VOMS for each individual. A shorter version of the VOMS used in pediatrics has recently shown to be 85% as effective as the original screening tool. The modified Vestibular Ocular-Motor Screening (mVOMS) is a simple, easy-to-administer diagnostic tool that consists of four task conditions (smooth pursuits, horizontal saccades, horizontal vestibular-ocular reflex, visual motion sensitivity) and can be administered in less than 2 minutes, which makes it more suitable for administration in a military training or operational environment. The Environmental Sensors in Training (ESiT) team at Walter Reed Army Institute of Research (WRAIR) partnered with a military unit to determine if mVOMS is useful to screen for mTBI symptomology in military personnel after blast exposure in training environments. At issue is the need for a reliable, easy to deploy and administer tool that can detect early signs of mTBI at the point of exposure to prevent long term negative health effects. We tested mVOMS on soldiers who were repeatedly exposed to blast during training exercises to evaluate the degree of symptomology they experience. None of the volunteers were clinically diagnosed with concussion but they were exposed to different degrees of blast overpressure, from approximately 150psi*ms cumulative impulse to 1000 psi*ms. These data were compared with a control group of soldiers with no exposure, who did not participate in the training events. This study was conducted during three separate military training exercises. All three exercises utilized heavy weapons and different types of charges. Approximately 20 soldiers were screened on each occasion, 15 exposed to blast and 5 not exposed. The mVOMS tool was administered on as many as 20 soldiers in a single hour by 1 test administrator. The soldiers were tested at four timepoints (baseline, pre-exposure, post-exposure, follow up). From across all three training exercises, we examined 58 pairs of data (pre-exposure v. post-exposure) for soldiers in the exposed group (n=43) and the control group (n=15). For the exposed group, the symptom that most commonly increased was dizziness and the task that most commonly elicited an increase in symptom reporting was horizontal vestibular-ocular reflex. There was a clear difference between groups, with the exposed group reporting approximately two additional elicited symptoms following blast than the control group (t(56)=2.22, p=.03). When comparing blast magnitude measured for each soldier to mVOMS score change, we observed a positive relation with blast overpressure. Thus, the greater the blast overpressure, the more concussion-like symptoms were reported. We explored a preliminary threshold of blast exposure-induced effects. Soldiers exposed to a magnitude of cumulative impulse over 500 psi*ms tended to report more mVOMS symptoms post exposure [r=.35, (n=15)] than those with lesser exposure [r=.10, (n=13)]. The results show that the mVOMS measure can be useful in detecting symptoms of mTBI post blast exposure, however, it may not be as sensitive as detecting symptoms in patients with diagnoseable concussion. More research is needed to evaluate the mVOMS in larger samples to determine its sensitivity and test candidate thresholds of cumulative impulse that trigger mTBI symptomology. It is relevant to note that per MACE2 instruction, the presence of some symptoms (e.g., severe or worsening headache) result in a referral to a higher level of care.
