Brain Injury and Vision Loss From Blast Trauma

This article is from November/December 2008 and may contain outdated material.

Sergeant David Emme remembers Iraqi kids running alongside his convoy. “They were making throat-cutting signs that seemed to mean ‘Ha-ha, we’re going to get you!’ But when I thought about it later, I realized they were actually giving us a warning—it was their way of communicating to us that something bad was about to happen. It was very pro-American, really. They were giving us good intelligence.”

Unfortunately, the messages weren’t understood. As Sgt. Emme’s truck rolled on, an improvised explosive device (IED) was detonated, changing his life forever. “I didn’t see or hear the blast. I just woke up a few seconds later not even knowing who or where I was. My driver started screaming my name and pulling me off the truck. It took about 15 minutes for him to get me to medical help.” Sgt. Emme sustained severe head wounds in the explosion. “They said I died,” he remembers, and without timely medical intervention, there is little doubt that he would have.

But Sgt. Emme was successfully resus­citated and worked on by a team of surgeons in the Green Zone, and a section of his cranium was removed and stored in his abdomen until the swelling of his brain subsided. Over the following weeks and months, deliriums and mental status upsets led to episodes of terrible con­fusion and combative behavior, with Sgt. Emme trying to pull his drainage tubes out and requiring physical restraint by hospital workers.

Barotrauma. The modern war on terrorism—and the terrors of modern war—have made alarming contributions to the annals of blast trauma, traumatic brain injury (TBI) and their ophthal­mic sequelea. In fact, barotrauma may constitute what Christopher Born, MD, calls “the fourth weapon of mass destruction.” In the Scandinavian Journal of Surgery, Dr. Born, who is professor and chief of trauma at Brown University, outlines grave responsibilities facing future physicians, not just in the military but in civilian life as well: “Injury from blast is becoming more common in the nonmilitary population. This is primarily a result of an increase in politically motivated bombings within the civilian sector . . . Civilian physicians and surgeons need to have an understanding of the pathomechanics and physiology of blast injury and to recognize the hallmarks of severity in order to increase survivorship.”¹

Mechanisms and Management of Blast Trauma

The detonations of IEDs create enormous and abrupt fluctuations in air pressure gradients, first with a shock wave of overpressurization and then with a compensatory wave of underpressurization and blast wind.²Individuals close to an explosion face a series of potentially lethal events:

• In the shock wave, gas-supported organs—lungs, bowels and tympanic membranes—are very susceptible to injury. But the eyes and brain are vulnerable as well, and blast wave velocity and duration may determine injuries to those denser tissues. In experiments with rat brains only a fraction of blast energy was absorbed by the skull, and even blasts that were too low to induce gross pathology nevertheless led to degenerative neuronal changes. In fact, neuronal injury may occur at pressures lower than those that cause pulmonary injury.³
• Projectile debris—and the violent displacement of the body itself—can cause penetrating and perforating wounds and traumatic amputations. And those are often accompanied by burn, crush or inhalation injuries.
• The hemodynamic, metabolic and inflammatory cascades launched by such massive wounds, including levels of IL-8 and IL-10 that are associated with multiple organ dysfunction syndrome, can hamper survival from blasts.⁴

Blast burden. IED survivors face challenges that range from the minor to the monumental: fractures, amputations, disfigurement, sensory deficits, cognitive and motor impairments, dysphagia, emboli and stroke, headaches, personality changes, visual and auditory disturbances, altered affect, hypersensitivities and dulled judgment.⁵ The mortality from blast violence has been reduced by rapid medical interventions, but blast injuries, by their nature, usually include eye, ear and brain trauma, so many soldiers returning home will need years of neurologic, psychologic, otolaryngologic and ophthalmologic follow-up.

“The majority of soldiers we saw were injured by a blast of some sort, rather than, for example, a gunshot wound,” said Prem S. Subramanian, MD, PhD. Dr. Subramanian, now an associate professor of neuro-ophthalmology at Wilmer Eye Institute, spent several years on staff at Walter Reed Medical Center in Washington, D.C., where he managed many patients who had sustained serious head and eye combat injuries in Iraq or Afghanistan.

Stop the bleeding, keep them breathing. For troops who sustain multiple injuries, a sober logic governs the sequence of interventions. “In combat theater, surgeons apply the ‘life, limb and eyesight’ approach to prioritizing injuries, with limbs and eyes earning equal attention, and both of those deferring to life-threatening injuries,” Dr. Subramanian said. “If patients had a severe intracerebral hemorrhage, for example, or subdural or subarachnoid hemorrhage, causing brain herniation or depression of their vital signs, obviously that would command the greatest precedence. Many would arrive at Walter Reed in severe shock because of blood loss or a closed head injury. If they were too unstable to remain under anesthesia for long, that, of course, limits the interventions that could happen.”

Soldiers within close range of IED blasts suffered very complex trauma, Dr. Subramanian said. “With a direct blow to the face, the facial skeleton absorbs tremendous amounts of energy, and these are injuries that no one in the past would have survived. These patients would have not only facial injuries but orbital fractures and anterior segment trauma, so a stepwise, team approach was needed. We’d have to deal with open-globe wounds first, and then facial and orbital fractures were handled in concert with ENT or oromaxillofacial surgery.”

Recovery Is a Goal (and a Process)

Four years after his IED trauma, David Emme is cognitively intact and emotionally animated and eager to share his experience. He correctly labels his TBI the “signature wound” of the wars in Iraq and Afghanistan, and has written his own version of his story called “A Good Whacking.”⁶ He is reminded daily of his injuries: head­aches, a sleep disorder, permanent hearing loss in one ear and odd, unpredictable problems with visual processing. “One day I needed to go to an address on Linden Street. I happened to find a street that I now know is called Liberty Street, but at that moment it clearly said ‘Linden’ Street. I’ve also missed airline flights because I misrecognized the information on tickets.” And there are fleeting motion hallucinations. “I’ll see something out of the corner of my eye—something running across the floor at the edge of my perception—but when I look there’s nothing there.”

The eye + the brain = questions. “Traumatic brain injury and its visual consequences are very difficult to write about. It’s like trying to catch the wind—we really don’t know a lot yet,” said Col. Robert A. Mazzoli, MD. Dr. Mazzoli is chief of ophthalmology and director of ophthalmic plastic, reconstructive and orbital surgery at Madigan Army Medical Center in Tacoma. He described a perplexing randomness that haunts the distribution of TBI. “There are some vets who have been in blasts and who may or may not have TBI. And there are others now in polytrauma centers who had to pass a certain threshold of injury, unfortunately, just to get admitted to those centers—multiple limbs lost, severe head trauma, burns, long-term coma. Is it surprising that they have vision problems, too? And then there are troops who walk off airplanes onto the tarmac and hug their kids in spite of concussive head trauma.”

Nevertheless, Dr. Mazzoli said it is useful to distinguish massive injuries that will obviously impair vision from more subtle insults to the visual pathway that are not easily isolated. “TBI and vision occupy a large spectrum. On the one end are the soldiers who have lost an eye and a good portion of their brain. On the other end are the mild TBI patients who got their head clocked, were seeing stars for a while, and might now have some difficulty reading. And in between are the folks who were in a blast and have substantial but silent anatomic damage.”

Locating the trauma anatomically. Dr. Subramanian has seen patients across that entire spectrum. The most baffling are those who present with no apparent eye trauma and no identifiable insult to the occipital cortex, but who are clearly visually impaired. “It’s hard to sort out visual loss that may or may not involve the anatomic structures of the visual pathway. We use multifocal electro­retinograms and visual evoked potentials to look at the functioning of the visual pathways. In a number of soldiers, the eyes looked pretty normal, but the electrophysiologic functioning was definitely not. So although anatomically things seem OK, the force of the injury was so great that perhaps the retinal or optic nerve function was somehow damaged. We postulate that one mechanism of injury involves some shearing of the optic nerve from its blood supply.”

From Combat to Care at Home

Like Sgt. Emme, Staff Sargeant Jason Pepper was on patrol in Iraq when he came upon the fury of an IED. The explosion fractured his skull, shattered his right arm and left hand, and blew shrapnel through his right orbit into his brain. The blast wave explosively ruptured the fellow eye, and Army surgeons were left with no choice but to enucleate what remained of both globes. Sgt. Emme and Staff Sgt. Pepper were both featured in the New England Journal of Medicine as paradigmatic examples of TBI.⁷

“A piece of shrapnel the size of a silver dollar still sits in my frontal lobe. That’s what severed my lower eyelid and shredded my right eye. I have some equi­librium problems and slightly slurred speech, some small nighttime seizures and short-term memory problems,” Staff Sgt. Pepper said. He also experiences nightmares that come and go, and sporadically encounters confusion with numbers. One of his symptoms might seem retinal in nature, except that his retinas are gone. “I have weird light flashes. They sort of start in one side of my ‘vision’ and go across to the other side. Sort of like when you hit your head—that sudden light that goes on.”

How the brain sees. An understanding of TBI in both blinded and sighted veterans will illuminate new frontiers of perceptual processing, Dr. Subramanian said. “I have seen a number of visually intact patients who nevertheless have difficulties in higher-order processing. I saw, for example, a soldier who demonstrated alexia without agraphia. It’s an unusual syndrome that was probably caused by a stroke following a head wound. I saw other patients who I’d describe as having visual confusion not fitting into an already-described syndrome in the literature, but rather a more diffuse visual difficulty.”

The patients, needless to say, are often more baffled than their physicians, Dr. Subramanian said. “We were trying, of course, to characterize their problems better, but due to their brain injury, the patients sometimes have a hard time explaining their symptoms. But it was clear that they had difficulty processing visual information. Visual spatial abilities would, in particular, be affected by their TBI. These were soldiers who had 20/20 vision and appeared to be intact from the eye back through the occipital cortex. So the problem is in the rest of the brain, where higher-order functioning happens. Fortunately, today we have better tools like functional MRI, PET scanning and diffusion tensor imag­ing to look at fiber tracts, neurologic pathways and brain metabolism to try to characterize better what parts of the brain govern these functions.”

One good example of a challenge, said Dr. Subramanian, is the patient with TBI who’s been intubated and sedated for three weeks and wakes up and realizes he can’t see out of one eye, or has double vision. “We often had to piece things together after the fact, to come up with a good explanation based on other injury patterns we had been seeing. We had to keep our suspicions up for things like arteriovenous fistulas, or other intracranial problems that led to strabismus or visual field changes.”

The helpful hand of research. Glenn C. Cockerham, MD, currently treats and studies veterans returning from the combat zones with multiple injuries, including eye and brain trauma. “Most injuries we see were blast-induced. Those may or may not include vision complaints. But any blast strong enough to induce brain injury can certainly damage the soft tissues of the eye and orbit, despite the use of protective head and eyewear.” Dr. Cockerham is chief of ophthalmology at the Veterans Affairs Health Care System in Palo Alto, Calif. “We’re trying to sort out brain versus eye injuries,” he said. “In addition to high-contrast visual acuity, we’re examining spatial contrast sensitivity and various visual field examinations. Classic teaching is that reduced spatial contrast sensitivity can suggest either a retinal injury or brain injury. These patients may have good visual acuity, 20/20 or better, but have abnormal visual fields, abnormal spatial contrast sensitivity and even color confusion.”

Facing the Future

Dr. Mazzoli said that the desire and the effort to keep TBI veterans in meaningful care is gathering momentum. “We are working to craft a congressionally directed ocular center of excellence. The Army, Navy, Air Force and the VA are collaborating on an entity that will allow us all to share patient information and best practices, as well as provide for nonsurgical visual needs, such as rehabilitation, for both visually impaired and blind veterans. The initiative is proceeding, but it has a while to go.”

That initiative would be welcomed by Staff Sgt. Pepper. “I was such a visual learner before, and now I have to try a new skill over and over before I learn it. I also go off the deep end a lot, over seemingly trivial things,” he said. “Here I was, living in the sighted world for 26 years, and then I woke up one day and I was totally blind. Now I have to rewire myself to use my hands as my eyes. My olfactory nerves were severed, too, so my senses of smell and taste are gone. Even my fingertips aren’t sensitive enough to learn braille.”

The American Academy of Neurology has also championed the needs of injured veterans. “The conflicts in Iraq and Afghanistan have created an emerging epidemic of traumatic brain injury among combat veterans. TBI is associated with cognitive dysfunction, post-traumatic epilepsy, headaches and other motor and sensory neurological complications.”⁸ The AAN position paper recommends, in part, that:

• The “DoD should undertake all steps necessary to permit the differential diagnosis of traumatic brain injury of all military personnel returning from deployment to measure potential exposure to percussive blasts, whether or not such exposure required or resulted in medical attention and whether such exposure may have resulted in TBI.
• “Given the likely high rate of post-traumatic epilepsy that soldiers with TBI will experience, Congress should authorize and the Veterans Administration should fully implement a national epilepsy program . . . available to all veterans with epilepsy and related seizure disorders.”

Renewing a life. After all the service and sacrifice for his country, and after all the surgeries and prosthesis fittings for his bruised body, Jason Pepper cherishes every moment of meaning in life. “It’s kind of funny, but when I was blinded four years ago, it opened my eyes. I realized it’s the little things that matter, the things that more people should stop to appreciate.” Among his appreciations are the support of his wife and daughters. “When my older daughter brought home arts-and-crafts stuff from school, she made sure it had bumps and foam and other things I could run my hands over so I could have a tactile experience with what she made. When she was not even 2 years old and I was hooked up to tubes and my arms were immobilized, she touched the only parts of me that she could. She sat next to me ever so gently and just held my pinky and touched my face and said ‘Daddy’s eyes . . . Daddy’s eyes are hurt.’”

Life continues for the Pepper family, and the athletically built Jason is not letting the loss of his eyes limit his navigation through the world. “I just went skiing in Snowmass and I conquered the mountain, which was my goal. I had a guide coaching me, but, funny enough, I hit a tree anyway. I think the tree suffered more damage! I’m waiting for the Colorado Wildlife Foundation to track me down and say ‘You owe us a tree!’ But when we found really open areas on the mountain, I just flew—no coaching, no audible cues, no nothing. Such a wonderful feeling, like everything was normal again. Just me and the mountain. And I was free.”

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1 Born, C.T. Scand J Surg 2005;94(4):279–285.

2 Ophthalmic Care of the Combat Casualty (Falls Church, Virginia: Office of The Surgeon General, Department of the Army, 2003).

3 Chavko, M. et al. J Neurosci Methods 2007;159(2):277–281.

4 Surbatovic, M. et al. Mil Med 2007;172(2):190–195.

5 Wallace, G. L. The ASHA Leader 2006;11(9):26–28.

6 www.relevantmagazine.com/forums/viewtopic.php?f=4&t=58&start=170 and enter “whacking” in the search field.

7 Okie, S. N Engl J Med 2005;352(20):2043–2047.

8 www.aan.com/advocacy/issues/tools/31.pdf.