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Brain Trauma Visual Dysfunction in Combat-related Mild Traumatic Brain Injury—A Review M Teresa Magone, MD, 1 Glenn C Cockerham, MD 2 and Soo Y Shin, MD 3 1. Staff Ophthalmologist, Department of Surgery/Eye Clinic, Ophthalmology Service, Veterans Affairs Medical Center, Washington, DC, US; 2. National Program Director, VA Ophthalmology Service, Palo Alto, California, US; 3. Chief, Ophthalmology Service, Department of Surgery, Veterans Affairs Medical Center, Washington, DC, US Abstract Approximately half of all military personnel who have served in the conflicts in Iraq and Afghanistan are reported to have some degree of combat-related mild traumatic brain injury (TBI). Although in civilian concussion injuries symptoms typically resolve within several weeks, blast-induced mild TBI may be accompanied by prolonged symptoms and afferent and efferent visual dysfunction. Most commonly near vision problems and photophobia are the presenting symptoms. A complete eye exam including vision testing, oculomotor function, and near tasking, is highly recommended after blast-induced mild TBI to detect and improve symptoms in this young patient population. A review of the current literature is presented. Keywords Mild TBI, visual dysfunction, combat-related injuries, TBI Disclosure: The authors have no conflicts of interest to declare. Received: January 16, 2013 Accepted: January 31, 2013 Citation: US Neurology, 2013;9(1):61–4 Correspondence: M Teresa Magone, MD, Veterans Affairs Medical Center, Washington D.C., Department of Surgery/Eye Clinic, 50 Irving Street NW, Washington DC 20422, US. E: maria.magone@va.gov Traumatic brain injury (TBI) is the signature injury of the conflicts in Iraq and Afghanistan. The Department of Defense defines mild TBI by loss of consciousness for up to 30 minutes, or an alteration in mental state and/ or memory loss, which lasts less than 24 hours and structural brain imaging yielding normal results. 1 Approximately 253,330 soldiers have been diagnosed with TBI since the year 2000. 1 The majority of these soldiers (76.8  %) were diagnosed with mild TBI while 17 % were diagnosed with moderate TBI, 2 % with penetrating and 1  % with severe TBI. 1 According to Lange, the overall numbers may be higher because many military personnel with mild TBI will never seek medical treatment. 2 Immediately after the TBI, post-concussion symptoms such as disorientation, slowed reaction time, headaches, and dizziness and blurred vision are common. 3,4 The natural history of mild TBI has been described to be self-limited with a predictable course. 5 In fact, studies show that most symptoms of mild TBI resolve completely by 6 months and only a small subset of patients has persistent symptoms beyond 1 year. 5–8 In recent years, observations of a more prolonged recovery after blast-related mild TBI have been discussed in the literature. 2,9,10 In a previous study, Wilk reported that among soldiers who reported loss of consciousness, blast mechanism of TBI was significantly associated with symptoms 3–6 months post deployment compared with a nonblast mechanism, although visual symptoms were not assessed in their study. 11 Explosive blast-related injuries are the predominant cause for TBI in the conflicts in Iraq and Afghanistan as a result of the preferred use of improvised explosive devices and improvised rocket-assisted mortars by the insurgency. The trauma to the brain from explosive blast injuries is thought to be more diffuse and complex than focal brain injuries from sports concussions commonly observed in the civilian population. 12–16 For example, malignant cerebral edema can develop rapidly over the course of one hour in blast-induced severe TBI as opposed to several hours to a day in closed head TBI. 15 Traumatic cerebral vasospasm in blast-induced TBI lasted for as long as © TO U C H M ED IC A L MED IA 2013 30 days compared to 14 days in closed head TBI. It has also been suggested that overpressure from the explosion may compress the abdomen and chest, inducing oscillating high pressure waves, which are transmitted upwards along the vessels, leading to perivascular brain damage. 16–18 In addition, hyperinflation of the lungs occurs, which can cause a vasovagal response leading to hypotension and possible cerebral hypoxemia. 16–18 Peskind recently reported decreased cerebrocerebellar metabolic rates in Iraq combat veterans with more than one episode of blast-induced mild TBI. 19 Significant brain injury can occur in blast-induced mild TBI. Several groups have recently diagnosed axonal damage in blast-related mild TBI patients with diffusion tensor imaging, despite normal MRI and CT studies. 20,21 Morey discusses a ‘pepper-spray’ diffuse pattern of white matter damage seen in Iraq and Afghanistan veterans with chronic mild TBI after blast injury. 20 These changes can appear as early as 1 month after the injury and extend further at 1 year. 20 Blast Injury Mechanisms There are several factors that can affect the degree of brain injury. At the time of the explosion a shock front is created followed by a blast wave, which expands until the pressure falls below atmospheric pressure. 16,17 Initially, the primary blast wave passes through body armor and bone, and is able to disrupt underlying tissues through embedded shear and stress waves. 13,22 Organ systems with high air content such as the pulmonary, gastrointestinal and auditory systems are the most susceptible, but overpressure also causes damage to the central nervous system, visual system, musculoskeletal and cardiovascular systems. 23 Secondary damage occurs when debris or fragmentation from the explosive device or surrounding objects penetrate the body. 24 Tertiary blast injury involves acceleration and deceleration forces, such as occur when a body is propelled and crashes into a fixed structure or the ground. 15 Quaternary injury occurs 61