Welcome to another online teaching module by the AANS. The current topic will be Penetrating Brain and Spine Injury with material prepared by Drs. John Cook, Chris Zacco, and Josh Meadow. The agenda, first we'll want to go over the background information including classification of penetrating brain injuries, principal differences between low and high velocity injuries, some good resources to refer you to for your own reading afterwards, and then some basic firearm and ballistics terminology. The next section will be on high velocity penetrating brain injury. This is what we most commonly think of when we think of penetrating brain injury, meaning gunshot wounds to the head. We'll start by reviewing the differences between civilian and military high velocity penetrating brain injury. We'll review demographics, prognosis, and predictors of outcome, assessment of penetrating brain injury, management, including medical and surgical complications. The next two sections will be relatively brief in comparison to the second, but low velocity penetrating brain injury, meaning knives and arrows, and then briefly penetrating spine injuries. With that, we'll get into some background information including classification, resources, demographics, and terminology. General classification of penetrating brain injury is, for the most part, divided between high and low velocity injuries. High velocity missile projectiles are considered greater than 1,000 feet per second. A good example is an AK-47. Low velocity missile projectiles are less than 1,000 feet per second. An example would be a .45 caliber handgun or shrapnel. And then very low velocity, typically knives and arrows. The principal differences between a low velocity sharp penetrating injury and a high velocity injury is that with low velocity injuries, there's significantly less kinetic energy. Therefore, these cause focal injuries based on the tissue damaged by the object itself. There will be direct tissue and vessel injury from the laceration, and a single injury pathway without ricochet or fragmentation of either the bullet or the skull. Ballistics do not apply to these low velocity injuries. There is no associated blast or cavitation injury. It is recommended that you get a CTA before considering removing the object, and this will best play in your operative approach as well. And these injuries may not result in loss of consciousness as it will not disrupt the brainstem or the reticular activating system. Three excellent resources include the Management and Prognosis of Penetrating Brain Injury published in 2001 in the Journal of Trauma, Injury, Infection, and Critical Care, the Guidelines for Field Management of Combat-Related Head Trauma published in 2005, and then Yeoman's Neurological Surgery has an excellent chapter, chapter 336 in the 6th edition. Now we'll get into some firearm terminology just briefly. So the first term you'll hear is caliber. The caliber of a weapon. So in a smoothbore firearm, this will be the diameter of the barrel, and this is expressed in inches. So a .45 caliber handgun has a barrel diameter of .45 inches. It can also be expressed in millimeters. Rifling are helical grooves on the inside of a barrel which give the bullet spin. Gauge. This is something you'll hear most commonly in shotguns, and this is the size or mass of a given bearing size needed to fit the bore of a firearm and is expressed as a fraction of a pound, meaning a 112-pound ball fits in a 12-gauge bore, and there are 12-gauge balls per pound. The ballistic coefficient is the property of a projectile that allows it to overcome air resistance, and this is different for each projectile. Magnum. This is the .44 Magnum. Everyone has heard of that term. This is extra propellant placed in a stock projectile, and this imparts more velocity as there's more propellant. Jacketing is a harder metal coating on the bullet. Two common terms, full metal jacket, and this allows for higher muscle velocity in a jacketed hollow point where the bullet itself has a hollow point that expands on impact, mushrooms, and causes a greater exit wound. So the definition of ballistics. This is the science of the motion mechanics underlying the propulsion, flight behavior, and impact of projectiles. It's typically used in the study of projectiles that is fired through a gun barrel, subsequently through a medium, air, and ultimately into a target. There are three components to ballistics. Interior ballistics is the science of motion through a gun barrel. Exterior ballistics is the science of motion of a projectile in a medium such as air. This is dependent on the shape, caliber, weight, initial velocity, and ballistic coefficient. And then terminal ballistics, the behavior of a projectile upon impact, and this is dependent on the penetration, tissue density, fragmentation, detonation, shape of a charge, blast over pressure, combustion, and incendiary features. The wounding energy is generally one-half mv squared from our basic physics. However, in very high velocities or even just high velocities at greater than 700 meters per second, the wounding energy is dependent on the power, which is P equals mv cubed. So again, these are more for the military weapons that get up to be very high. And note that 700 meters per second, not feet per second. So wound or terminal ballistics. So when a projectile hits tissue, it tumbles. The maximum damage occurs when the orientation of the projectile is 90 degrees to its long axis. So with this tumbling effect after it hits a tissue, it will therefore is the reason why there's a larger exit wound than an entry wound. Yaw is a term that is a rotation of a projectile around its long axis, or imagine it rolling. Nutation is a rocking or swaying or a nodding motion within the axis of the rotation. Damage done to the brain parenchyma is proportional to the energy imparted to the surrounding tissues. It is related to the ballistic properties of the primary projectile and the secondary projectiles, whether that initial bullet fragmenting or even bone fragments from penetration can become projectiles themselves, secondary projectiles, and cause damage. And also the tissue density of the brain. The ability of a projectile to penetrate the cranium is dependent on the shape of the projectile, the angle of impact, and the consistency of the tissue that it struck. Next in discussing wound ballistics, we'll go over positive pressure waves. This includes impact shock waves, juxtamissile pressure, longitudinal shock waves, and ordinary pressure waves. This is taken out of Yeomans. First is the impact shock wave. This precedes the strike of the projectile and has little effect on the tissue. Next is juxtamissile pressure. This is the pressure exerted by the projectile on the brain tissue immediately in the path of the projectile. It causes direct injury from the projectile on the tissue and it creates a permanent tissue injury tract or cavity. Longitudinal shock waves. Starts immediately after impact and travels in concentric spheres ahead of the projectile. Lastly, we have ordinary pressure waves. These are generated as the projectile transfers kinetic energy to the parenchyma and creates a temporary cavity. Cavitation is an important feature of penetrating brain injuries and can cause tremendous damage. It is created by the summation of positive pressures that we just went over and results in a cavity surrounded by compressed parenchyma. This initial positive pressure is transient and is related to the kinetic energy of the projectile. The brain being relatively inelastic can increase the injury 10 to 20 times the diameter of the projectile. The negative pressure following the dissipation of the initial tract causes implosion of the tract and sucks in bone, hair, clothes, etc. This rapid expansion and collapse of both the positive pressure, the cavitation, and that negative pressure can happen on several cycles and can reverberate through those several cycles, decreasing with magnitude each time until the energy has dissipated, but this can cause a devastating injury. Injury mechanisms. The pressure generated in penetrating brain injuries is dramatic. They are felt to create gradients across the foramen magnum and impart distorting forces to the brain stem. This can lead to some specific phenomena seen in penetrating brain injuries, such as dramatic spikes in mean arterial pressure and ICP in the minutes following penetrating brain injury. It has been described that the increase in ICP lasts longer than the MAP increase, predisposing those patients to ischemia. Other features include apnea, massive surge in catecholamines, release of thromboplastin, leading to coagulopathy. Modes of injury. These are ways that we use to describe an injury. So a penetrating brain injury is a projectile enters the skull but does not exit. A perforating brain injury, the projectile goes through and through the skull. Tangential injury is where the projectile bounces off the skull and then indirect. Here's just a brief chart taken out of Yeoman showing the percentage of patients that survive these injuries in 41 hours. You can see a perforating injury can be devastating. Here's a good example of a perforating injury. You can see the tremendous pneumocephalus, the combination of the bone, and the fact that the bullet went through and through the skull. With this next section, we'll get into high-velocity missile penetrating brain injury, or something we more commonly call gunshot wounds to the head. So let's distinguish between civilian and military high-velocity penetrating brain injuries. Much of the information we've gotten for penetrating brain injuries is derived from military experiences, although there are some studies on civilians as well. But a civilian gunshot wound to the head tends to be fatal. It is thought this is because these are typically contact or near-contact injuries rather than maybe from more of a distance in the field of combat. There's direct damage from the bullet. There's a tremendous amount of energy imparted that disrupts the parenchymal vessels, as we've discussed. There's been several studies, and this has been validated even in more recent studies, that most of these injuries are instantaneously fatal to seeing in approximately 71% of victims. The mortality is 14% within 5 hours, 13% within 5 to 48 hours, and less than 2% survive at greater than 48 hours with this initial study. CDC estimates that the overall mortality of gunshot wounds to the head is 94%. Military craniosclerical battle wounds have a better prognosis due to the presence of body armor, which absorbs the energy, the predominance of shrapnel injury and not primary projectiles, and the prevalence of blast-induced traumatic injuries as opposed to a primary penetrating brain injury. So again, we'll go over the velocity. A typical military M16 can be greater than 3,000 feet per second, a civilian handgun somewhere between 700 and 1,600 feet per second, and a civilian rifle can still, especially in modern times, are approaching some military weapons in their velocities. Let's talk about contact and near-contact injuries. An autopsy study by Freytag showed tract injuries from ricochets in 82% of these, so there's a secondary injury component as well. There's a permanent cavity also surrounded by an ischemic ring. The survivability is determined by the path of the projectile and the amount of tissue destruction. Alterations in consciousness are extremely common in penetrating brain injury. Demographics, at least we'll talk about civilian gunshot wounds now, so it's predominantly a male problem in the third or fourth decades of life. 50% of these are homicide, 46% suicide, 4% accidents is the approximation. 78% of homicides are black, 86% of suicides are white. And while penetrating brain injuries account for only 10% of TBIs, they account for 44% of TBI-related deaths. So let's get into prognosis and predictors of outcome of gunshot wounds to the head. This is from the military, and you can see that 35% to 40% of all combat deaths are from brain wounds, and this is just historically going through. And generally speaking, we've gotten better with our treatment as we've gone from the Civil War into more modern times, and that makes sense with advances in medicine. As far as civilian injuries, you can see a breakdown We consider these low-bar injuries, a unilateral multi-low-bar injury can have a higher mortality at 72%, mid-sagittal plane being crossed will increase mortality at 77%, mid-coronal plane, 84%, and both the mid-sagittal and mid-coronal plane being crossed, 96% mortality. Here's a picture of a penetrating brain injury that goes through the thalamus. There's a subdural as well, and this patient did not survive. Here's a zona fatalis injury, again considered to be an unsurvivable injury. It goes through and through at the level of the ventricles and the top portion of the brain stem. This is just one axial cut with a dramatic amount of hemorrhage, but this hemorrhage did encompass the brain stem as well, and this patient was dead on arrival to our center. So some predictors of outcome. Historically, positive predictors, and these would make sense, younger patients with better level of consciousness and pupillary reaction to light and less structural injury to parenchyma. Older patients, just as with closed injuries, do worse, but this is confounding because most of these patients are younger. The type of injury makes a difference. So suicide and then primary military gunshot wounds due to the higher velocity of the projectile have worse outcomes. Shrapnel and shell wounds do better. And then the caliber can make a difference, although there's multiple confounders. A higher caliber weapon would have a higher kinetic energy and therefore cause more damage. Please note that most civilian deaths seem to be due to suicide, meaning close-range injuries, and there's more injury with tumbling, mushrooming, fragmentation of the projectile. Other predictions of outcome include hypotension, which increases mortality just as with closed head injury. GCS, which is the strongest indicator of outcome in mortality in that it's been validated in a recent publication, which we'll go over. Less than 8, shown in multiple studies, has a worse outcome. Pupillary size and reactive delight, so unequal and fixed pupils, indicate a worse outcome. And then injuries with elevated ICP, meaning greater than 20, within the first 72 hours have a worse outcome. Imaging characteristics associated with outcome. Bihemispheric injuries seem to do worse, although maybe not bifrontal. Multilobar injuries, injuries involving the ventricles, cisternal effacement seen on CT scan, presence of intraventricular hemorrhage, midline shift, and extra axial hemorrhage. And we'll get back to those last two with the recent publication. Predictions of outcome from a study by Hoffbauer in 2010. This was a retrospective cohort of 85 patients over 16 years of age. All had CT scans. All were civilian injuries with a mix of suicide and non-suicide. Significant predictors of outcome included on imaging, bilobar or multilobar injuries and intraventricular hemorrhage. Those that benefited from aggressive surgical intervention included those with a GCS greater than 8, those with reactive pupils, and a single lobar injury. So this is a more recent paper I've referenced earlier, put out in 2004 in the White Journal in May by Dr. Arabi. This is a two-year retrospective study of prospectively collected data from a data registry from the Office of Chief Medical Examiner in Baltimore and nine participating hospitals in Maryland. They asked two questions. They asked how many died of civilian gunshot wounds to the head and if they could identify any predictors of good outcome as defined by Glasgow Outcome Scale 4 and 5. There were 786 patients in this study reviewed. Medical and surgical management was guided by the Braintomer Foundation and the AANS-CNS guidelines. Within the study, 91% died in total. 75.6% died at the scene, which is similar to historical value of 71%, and 24.4% reached a hospital. Of that 24.4% that reached the hospital, 61.5% died ultimately, and 38.5% of that 24.4% completed their acute care stay. This made for a total of 9% of the patients out of 786 that actually completed their acute care stay. They then did a univariate and logistic regression analysis of a subset of patients from the primary author's institution, which was shock trauma. This is 69 patients, of which 48 were resuscitated. And this represents the largest subset of patients of the survivors that reached the hospital from reaching shock trauma. So again, 48 of those 69 patients that reached this institution were resuscitated. 21 were dead on arrival. 66.7% died, and 33.3% survived acute care to discharge. Of these patients, 9 only had superficial wound care, 5 days of antibiotics, and no craniotomy. 15 had a craniotomy and debridement of skin, skull, dura, and brain in association with removal of easily accessible retained bone and metal fragments. They also had a watertight closure of dura and skin with post-op antibiotics. 5 patients got decompressive craniotomy, either preemptively or secondary to failure of medical management to control ICP. Their univariate analysis had 11 variables, age, sex, GCS after resuscitation, ISS, or injury severity scale, abnormal pupillary response, or APR, intravenricular hemorrhage, crossing of the X, Y, and Z planes, sesternal obliteration, midline shift, intracranial hemorrhage, and then surgery. Predictors of outcome included emission GCS, transgression of the X, Y, and Z planes, surgical intervention, abnormal pupillary response to light, obliteration of basal cisterns, intraventricular hemorrhage. Notice in this particular study there is an absence of intracranial hemorrhage and midline shift predicting outcomes. And this is different from more historical studies. They then did regression modeling. Surgery was not selected for inclusion in the final regression model due to high correlations with certain variables in regards to whether or not surgery was done. That left them with four regression models, each with three variables found to be significant in the univariate analysis. And these were age, obliteration of basal cisterns, and intracranial hemorrhage. There was a fourth variable that rotated among GCS 9 to 15, normal pupillary reaction to light, no intraventricular hemorrhage, and little transgression of the X, Y, and Z planes. In their conclusion, they found predictors of favorable outcome included a post-resuscitation GCS of 9 to 15 relative to a 3 to 8 and not meeting statistical criteria but was close was the presence of basal cisterns. When GCS was excluded from the regression modeling, predictors of favorable outcome included normal pupillary reaction and lack of transgression of the X, Y, and Z plane. Important imaging findings included the trajectory of the projectile being crossed into the X, Y, and Z planes, obliteration of the cisterns, and intraventricular hemorrhage. So here's a picture showing the trajectory of the bullet. You can see on the far right in the Z plane going in a vertical direction, so there's your Z plane, and obviously X and Y from the axials. Here's something showing, this was almost straight through, so not a lot of, so just crossing two of the axes and showing some blood in the basal cisterns and some effacement there. And here's lobar injuries after penetrating brain injury. And so this is something I commented on earlier where multiple lobes seem to do worse. However, we've had several at our institution in the last couple years of people attempting suicide, taking that traditional approach to shooting themselves at the temple but being too anteriorly and really just damaging the frontal lobes, the frontal poles during their injury, which did not turn out to be fatal. So here are some conclusions from Dr. Ravi's study. This showed that 30 to 50 percent of patients who admitted alive to the hospital can survive to discharge. Bear in mind that the vast majority of patients do not make it alive to the hospital. In this study, only 29% made it. At shock trauma, the 10-year acute care mortality rate was 61%, and it's an interesting note that it is estimated that less than 20% of civilians with penetrating brain injury will actually get a chance to have neurosurgical management. This is important to keep in mind because if they do get you and they are viable, neurosurgical management can certainly make a big difference. GCS greater than 8 was the most important predictor of favorable outcome as found in this study, and that's also been shown historically. And then in their analysis, when GCS was excluded, the next most important variable was normal pupillary reaction to light. Others included basal cisterns being open, the projectile not crossing the coronal or sagittal planes. As opposed to closed severe head injury, severe disability or vegetative state was less common in survivors of civilian penetrating brain injury. That might just be a reflection of most die, and if they don't die, they might do well, but it also could argue to being aggressive with those that seem to have some good predictors. And again, in contrast to previous studies, intracranial hemorrhage and midline shift were not found to be significant predictors within this study in penetrating brain injury. So now we'll get into the assessment of gunshot wound head. Physical exam, when you first see them, you're going to evaluate for brain stem dysfunction. You're essentially assessing for viability, what's their pupillary status, their oculosyphalic reflex or cold calorics or cough or gag. Recommended to shave the head fully to inspect for both entry and exit wounds and possibly to apply pressure to control bleeding. Imaging, I think most get CT scans now and then pretty early CT angiograms done. This will identify mass lesions, the trajectory of the bullet, any fragments of either the skull or the bullet, pneumocephalus, whether there's sinus involvement. You can quantify the amount of edema and obviously helps with surgical planning. I personally advocate for vascular studies early. This is particularly important when entering near the terion, orbital cranial cerebral injuries when a fragment passes through two dural compartments. Angiogram is the gold standard for this, however, not necessarily practical, particularly when a patient first shows up, which is why I rely on CT angiograms and advocate for a repeat in a week to look for pseudoaneurysms if appropriate. MRI and plane scans have limited role. So management, management will start with pretty similar to closed head injuries. So an ICP monitor, and this is really, this practice is extrapolated from the closed head injury data. As we already mentioned, intracranial hypertension is associated with poor outcomes. There's been no randomized controlled trials for this, so it's all class three evidence. So because we don't know not to do it, typically we do it. Infection prophylaxis, it's often difficult to obtain causative organisms. We can assume skin flora. Most recommend prophylactic antibiotics anywhere between five to 14 days and make a broad spectrum depending on the wound and other factors. Anti-epileptic drugs are recommended just as with closed head injuries. All the randomized controlled trials that look at prophylactic anti-epileptic drugs in head injury typically exclude the penetrating brain injury. As with closed head injury, class three data seems to support that. It helps prevention of early seizures, but it has no effect on development of late seizures. Personally, I give seven days of anti-epileptics and stop them. I don't know if anybody sees start again, but I know plenty of people prefer to give longer durations of anti-epileptics with penetrating head injuries. So within surgical management, the goals are to evacuate mass lesions, debris the wound, and get primary closure of the skin edges. Talking points we'll go over in the subsequent slides include debrisment and repair of the scalp, craniectomy versus craniotomy, debrisment and watertight closure of dura, debrisment of devitalized brain, debrisment of retained fragments, and repair of the skull base. With the debrisment and repair of the scalp, you want to do a thorough irrigation and debrisment of the scalp and clean out the wound with a proper two-layered primary closure. This is important to prevent infections with either staph or grand negative rods. It's also important with poor wound healing. There can be a lot of devitalized tissue and thin tissue with a jagged entry, so it's important to get to clean and healthy skin to get your closure. Patients with ventricular injuries are highly susceptible to CSF leaks. The next talking point is craniotomy versus craniotomy, which obviously gets a lot of attention in the closed head injury world as well. A few studies, or two studies we have here showed, in a retrospective review, no difference in outcome between the two. In another study, it showed that craniotomies had a worse Glasgow outcome scale at 6, 12, and 24 months. There seemed to be no difference in evacuation times, and they also noted in the military they stopped saving the bone in Operation Iraqi Freedom. That said, currently, there does seem to be an emerging trend from Operation Iraqi Freedom to do early damage control decompressive craniotomy with severe global injuries with midline shift, edema, and obliteration of the basal cisterns. This is done either primarily and preemptively, or after failure of medical management. A more limited operation with a craniotomy as opposed to craniotomy can certainly be considered with debridement of local injury. If there are no signs of midline shift or intracranial hypertension. Debridement and watertight closure of the dura. This is an important consideration when penetrating brain injuries have concomitant exposure of the air sinuses or complex scalp laceration at risk for not healing. And sometimes the dura is lacerated as well, so it's hard to get a good closure there. So you can either use suturable duragen or onlays to supplement it, and then obviously pericranium is another good option. Debridement of devitalized brain is a controversial discussion matter. Obviously, this necrotic brain tissue can bring up inflammation and neuroinflammation and worsen edema. Civilian practices are traditionally shaped by the military experiences. I think, frankly, hemorrhagic and contused brain, that's obviously necrotic. I'll certainly take some of that, but I'm not aggressive with it. Debridement of retrained fragments. This is something that's gone through some evolution over the years. Retained fragments were traditionally thought to be a potential source of infection. Again, just as earlier with the devitalized brain, civilian practices are traditionally shaped by military experiences. Currently, it is felt that adequate superficial debridement is enough and that there is no need to aggressively chase or debride the deeper fragment. Here's some of this military experience we talked about. Harvey Cushing in World War I did a full debridement and tried to get every fragment. In World War II, they did minimal debridement. In Vietnam, they did maximal debridement, even if they had to do multiple craniotomies and it was found to show increased operative M&M and the risk outweighed the benefit. Here's some military experiences historically with debridement. In terms of minimal debridement, can this be effective? There's a study by Grinnell et al. It was a retrospective review of 148 patients with local debridement and dural closure. It seemed to have fairly good results. M&M, meaning morbidity of 8%, mortality of 6%. Another study out of Israel and Lebanon evaluated 116 patients with local debridement, hematoma removal, and dural closure without fragment removal and a mortality of 26%. And lastly, a study with 32 patients that just had simple wound closure. These were higher functioning patients with a GCS greater than 10 that got less than 6 hours of presentation and no transsylvanian trajectory, no hematoma, and they had no deaths and one infection. So again, here's some studies showing that minimal debridement can certainly be quite effective. So who do we consider good surgical candidates? Again, extrapolated from military data but poorly. There's ethical considerations involved. Lots of class 3 evidence but no class 1 evidence. But generally, patients that are determined viable. Those with GCS greater than 8, intracranial hematoma you may be able to take out and make a big difference. A CSF leak can certainly be a surgical candidate if they're viable. And then surgery performed when other indications are discovered during their intensive care stay. Options for surgery include craniotomy, minimal debridement and craniectomy, minimal debridement, meaning local wound care, antibiotics, and skin closure is a reasonable option for small fragment injuries without devitalized scalp, air sinus injuries, ventricular penetration, or vascular injury. Lastly, we'll talk about repair of the skull base. Military and blast injuries are especially prone to CSF leaks from anterior menopausal injuries. Look for signs of skull base defects in your preoperative planning and initial assessment, and repair a titanium mesh, local pericranium, fat temporalis fascia, and muscle. The next section we'll discuss is complications that come from high-velocity missile-penetrating brain injuries. These complications come from four main areas including vascular CSF leaks, intracranial infections, and post-traumatic epilepsy. Okay, getting back to the vascular complications now, there's two main areas. One are vascular injuries to the vessels themselves, and then also vasospasm. The vascular injuries to the vessels themselves include four main areas. One is traumatic intracranial aneurysms. There's also traumatic extracalvular aneurysms, dissections, and AV fistulas. Traumatic intracranial aneurysms, the incidence is found between 3% and 40%. And the literature states this usually varies with the timing and the sensitivity of the imaging modality used. Earlier imaging with angiography tends to reveal more pathology. The guidelines recommend angiography with patients at risk for traumatic intracranial aneurysm, and those risk factors include orbitofacial craniocerebral injuries, and injuries near the terion in patients with an intracranial hematoma outside of the primary tract or near there even. When you have identified a traumatic intracranial aneurysm, follow it closely. There's significant early rupture risk if there's an interval increase in aneurysm size on serial imaging. Intracranial aneurysms have unpredictable rupture rate. The larger ones rupture sooner, and the smaller ones do tend to heal. Generally speaking, endovascular treatment is considered safe. Decisions on how to treat these, either be it endovascular or open vascular techniques, is largely treated as you would in non-traumatic cases and on a case-by-case basis. Dissections is something else you can see with penetrating brain injuries. Treatment options vary depending on whether there's an aneurysm or no aneurysm. If there's an aneurysm, options include stenting and stent-assisted coiling. If there is no aneurysm, generally antiplatelet therapy is sufficient. However, these may require a stent if the patient develops a stroke or a flow-limiting intimal flap. Vasospasma is the other main classification of vascular complication with penetrating brain injury. Suffice to say, it's hard to tease this out as there's no primary literature base to come up with good solutions, but it certainly does exist. However, studies that have been done show no differences in outcome. And you would treat this just as you would treat vasospasm outside of trauma. Vasospasm, a study by Bell et al. from Operation Iraqi Freedom and Operation Enduring Freedom, showed a 50% incidence of vasospasm peaking at 14 days. They were able to follow it with TCDs. There's no difference in outcome of those treated endovascularly versus conservatively, but endovascular had fewer days of vasospasm. CSF leaks, this is most highly correlated with development of infection. Again, a fairly wide range, 49% to 63%. The mortality of these infections in one study was as high as 22.8% with a CSF leak versus 5.1% without, underscoring the meticulous operative technique in repairing skull base injuries and preventing the leak. Intracranial infections are another complication. Keep in mind, penetrating brain injuries are contaminated wounds, usually with skin flora. Risk factors for infections include CSF leaks, transventricular trajectory, and injury to air sinuses. Guidelines do recommend prophylactic antibiotics. The current trend is a thorough irrigation and debridement of scalp wounds with two-layer closure. It would debride only the superficial bone and fragment and do not chase deep foreign bodies. Bear in mind, superficial debris may have been drawn into the wound during the negative pressure phase of cavitation. Post-traumatic epilepsy occurs between 34% and 50%, and twice that for closed head injury. Retrained bone fragments have not been definitively shown to be independent risk factors for developing of epilepsy. Various analyses have failed to show a clear-cut and consistent relationship with several suspected potential risk factors. The guidelines suggest one week of prophylactic antiepileptics, and this is what I stick to, although I do know many practitioners, due to the fact that there's twice the risk, will provide slightly longer courses, particularly with the increasing use of Keppra, which has a relatively low side effect profile. Okay, gunshot wounds to the head. Now let's move into low-velocity penetrating injuries. These next sections aren't nearly as long. This will include both spinal. So the principal differences, we've touched on this before, so low-velocity injuries have less kinetic energy. There's a single injury pathway and no ricochet or fragmentation. There's no associated blast injury or cavitation. There's no negative or positive pressure waves, so the effect of debris is less of a concern. Injury can be somewhat more focal than generalized, although that picture below obviously shows it dramatic. So again, we touched on differences in pathology. In low-velocity sharp injuries, ballistics do not apply. There's direct tissue and vessel injury from the laceration and the object that causes the injury itself. This is thought to cause more of a focal injury based on the tissue specifically damaged by that object. And again, mentioned previously, these injuries may not result in loss of consciousness unless the brainstem itself is involved in the injury. Considerations based on the entry site. So considering it near the orbit, there's no bone to protect entry into the skull here, so that's an area of vulnerability. Injuries to the frontal fossa can enter either through the orbit or to the terion. Injuries to the terion, as mentioned, can be dangerous for vascular injuries. Injuries to the temporal fossa can be dangerous due to the relative proximity of crucial nearby structures. A trajectory that goes anteriorly can injure the cavernous sinus, the carotid artery, or the cella. A posterior trajectory can injure the basilar artery or brainstem. And lastly, injuries to the occipital and cranial-cervical junction can put the vertebral artery at risk. So evaluation of low-velocity penetrating brain injury. Again, advocate CT scan and CT angiograms. A caveat, this can sometimes be wood, which can be hard to see on imaging. These objects can fragment more and can harbor more infections. Medical management includes tetanus shot and antiepileptic. Again, Keppra seems to be the most popular choice now. And then prophylactic antibiotics for 7 to 10 days. Surgical management. So remove the object in the operating room after adequate and generous exposure has been obtained to allow surgical control of potential bleeding. If the weapon has already been removed, local debridement, washout, meticulous primary closure of skin may be appropriate. Try to have your operative skin incision to incorporate the entry laceration. And then same surgical principles apply. Adequate exposure, debridement and hemostasis, repair of the air sinus and skull defects, and dural closure of primary pair of skin laceration. Complications of these injuries are similar to the high-velocity gunshot wounds infection. There's no primary evidence to support it, but generally speaking, most use 5 to 10 days of broad-spectrum prophylactic antibiotics. Vascular injury can certainly occur, lacerations to vessels with intracranial hemorrhage, pseudoaneurysms. So again, the importance of a CTA with these evaluations. And just with penetrating brain injury, you can consider delayed CT angiograms. Pseudoaneurysm has been found in delayed fashion, including one a week and even one to three months after injury. Okay, shifting gear to penetrating spine injuries, just very briefly. So these typically occur in young males. As far as location, thoracic greater than cervical greater than lumbar in correlation with the number of vertebral bodies. 75% of these injuries cause a complete spinal cord injury. If it traverses the canal, 88% are complete. If it did not, 78% can be incomplete. Intuitively, non-missile penetrating injuries, NIVs, are less likely to result in spinal cord injury. Workup includes X-ray, CT, CT angiogram, and MRI if possible. Be mindful of vascular injury and pseudoaneurysm formation with these, just as with injuries to the head. Surgery, the role is somewhat more controversial. Indications include progressive neurologic decline, CSF leak, bony destruction resulting in instability, and infection along the tract. Here's a case we had at my institution that showed an injury that would not have caused bony instability in the spine. You can see it there on this left-sided image. It goes through and injures one pedicle in the rib head. And portion of the lamina. But what this did do was cause a CSF leak and a CSF effusion in the lung, which caused respiratory compromise. So we ended up going in and doing a laminectomy and tying off the nerve root to stop the CSF leak. Okay, so now we've gotten to the summary. Let me just go back through a few key points. Low-velocity injuries tend to be more focal, with damage localized along the injury tract itself. There's no blast or capitation injuries, as with high-velocity penetrating brain injuries. Civilian gunshot wounds tend to be fatal. 74% die at the scene, and ultimately around 90% die. But bear in mind, 30% to 50% of those that make it to the hospital alive can survive to inpatient stay and can be discharged to rehab. Predictors of good outcome include post-resuscitation GCS greater than 8, normal pupillary reaction, and lack of transgression of the X, Y, and Z planes. Important imaging findings certainly are trajectory of the projectile crossing the X, Y, Z planes, obliteration of the cisterns, and intraventricular hemorrhage. Initial CT and CT angiogram is encouraged. Consider repeating the CT angiogram at one week and possibly at three months to look for pseudoaneurysm formation. Medical management can certainly include ICP monitors in severe injuries with depressed GCS or suspected elevated ICP with edema. Prophylactic antibiotics are encouraged. Prophylactic anti-epileptic drugs are encouraged. I typically recommend seven days for this, and then stop and treat again if they have seizures. But again, as I mentioned earlier, many of my colleagues will treat longer due to the higher prevalence of seizures and penetrating brain injuries. Those patients that benefit from aggressive surgical interventions are younger patients, those with GCS greater than 8, patients with reactive pupils, and a single lobar injury. The surgical options used in penetrating brain injury include superficial debridement. This is wound care with a two-layer closure, five to seven days of antibiotics, and no craniotomy. For focal injuries without signs of midline shift or cisternal effacement, a craniotomy with debridement can be effective. You get debridement of the skin, the skull, dura, and brain, and associated with removal of easily accessible retained bone and metal fragments. Watertight closure of the dura and skin with post-op antibiotics is also recommended. The practice of getting every last fragment and piece of bone out is not being used right now. With more malignant injuries with immediate signs of edema or mass effect, preemptive craniotomy can be performed or certainly can be done secondarily after failure of medical management to control ICP. With penetrating spine injury, again, indications for surgery are somewhat controversial and evolving, but at this stage, I think most would agree that indications include progressive neurologic decline, CSF leak, bony destruction that would cause instability, and infection along the injury tract. So thank you for your attention tonight. If you have any questions, please feel free to contact us, and I'll be glad to answer via email.

AANS

online teaching module

Penetrating Brain and Spine Injury

Dr. John Cook

Dr. Chris Zacco

Dr. Josh Meadow

low velocity penetrating brain injuries

high velocity penetrating brain injuries