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Emergency management of missile injuries to the brain: Resuscitation, triage, and preoperative stabilization
Emergency Managementof Missile Injuries to the Brain: Resuscitation,Triage, and Preoperative Stabilization T. FORCHT DAGI, MD Until the end of the nineteenth century, penetrating missile injuries of the brain usually were dismissed as fatal. With the advent of modem surgical technique, of battlefield radiology, and particularly of antisepsis, rapid and meticulous surgical debridement resulted in diminished mortality.’ Following the end of the Korean War, and especially since the Vietnam conflict, the focus of attention has shifted from simple survival to improvement of functional outcome in both the military and the civilian setting. Initial resuscitation and rapid evacuation from the scene of injury have come to be recognized as two of the most salient factors in achieving this goal. The treatment of penetrating brain injuries has evolved with each succesive conflict. During the France-Prussian War, it was shown that modem surgery could be carried out on the battlefield. World War I proved the efficacy of vigorous surgical intervention and of battlefield radiology. ’ The Spanish Civil War demonstrated that blast effect was a significant component of craniofacial injury after aerial bombardment. During World War II, the importance of initial dural repair and antibiotic medication was first proposed, then debated, and finally universally acknowledged.2-4 The Korean War confirmed the effectiveness of early evacuation and initial definitive operation in improving survival and reducing infection.2.5 The civil disturbances in Belfast took place so close to the neurosurgical center that the natural history of penetrating injury could be studied virtually from the moment of injury.6 During the recent Lebanese conflict, all Israeli soldiers with head injuries were evacuated to a single institution, and, for the first time, the place of computerized tomography (CT) in combat neurosurgery could be evaluated. Finally, in the wake of the Vietnam conflict, the Vietnam Head Injury Study (VHIS), a unique cooperative effort between the U . S . Armed Forces, the Veterans’ Administration, the American Red Cross, and From the Neurosurgical Service, Walter Reed Army Medical Center, Washington, DC. The opinions contained herein are the private views of the author and are not to be construed as official or reflecting the views of the Department of Defense or the Department of the Army. Manuscript received September 16, 1986; accepted September 23, 1986 Address reprint requests to Dr. Dagi: Neurosurgery Service, The Walter Reed Army Medical Center, Washington, DC 20307-5001. Key
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Words: Gunshot wound, head injury, resuscitation.
the National Institutes of Health, was established to register and study outcome after penetrating head injury. The VHIS has followed a large population using sophisticated epidemiologic, radiologic, and neuropsychologic techniques for more than 18 years. A great deal of data that was lost in the past, when injured veterans were not aggressively followed beyond discharge from the hospital, is now being collected and studied.’ A number of recurring concerns characterize the literature on penetrating missile injuries of the brain: 1. The practical significance of distinguishing between high velocity and low velocity wounds. 2. The importance the wounded.
of early transport and treatment of
3. The definition of what constitutes gical debridement.
adequate
sur-
4. Specific methods of dealing with complex wounds involving the orbit, the air sinuses, and major vascular structures. 5. The management
of cerebrospinal
fluid fistulas.
6. The prevention and diagnosis of acute infection, of delayed abcess, and of hematoma. 7. The epidemiology seizure disorders.
and prevention
of posttraumatic
More recently, the epidemiologic and preventive medicine literature has reflected an increasing sensitivity to the issue of firearm injuries as a problem of public health.8 Because of the evidence that initial resuscitation and evacuation play a crucial role in the ultimate outcome of penetrating missile injuries of the brain, it is important that those involved in emergency medicine be aware of recent developments in the management of these injuries. This review will focus on these developments and, more briefly, on evolving concepts in ballistics and pathophysiology, in surgical technique, and in prognosis. These subjects are particularly important in view of terrorist attacks that have threatened populated urban centers with unfamiliar battlefield injuries. TERMINAL BALLISTICS: DETERMINANTSOF THE DEGREE OF INJURY
Injury to the brain is a function of the quantity of energy release over time; this is reflected in the volume and location of tissue damage. The traditional approach divides pene-
DAGI n MISSILE INJURIES TO THE BRAIN
trating missile injuries into high- and low-velocity categories, associating the severity of the wound with the muzzle velocity, mass, and calculated energy content of the missle.9.‘0 By convention, high velocity exceeds 2000 ft/sec. Most modern high-velocity rifle bullets easily surpass 2500 ft/sec. Most handgun ammunition ranges in velocity between 800 ft/sec and 1400 ft/sec. Typical penetrating fragments or shrapnel, in contrast, are estimated to strike at a velocity of 600 ft/sec or less. Most survivable penetrating cerebral injuries in war are caused by shrapnel or other fragments with attenuated or decayed energy levels. The energy (E) released in tissue depends in part on the missile mass (M) and velocity (V) at time of impact, and in part on the conditions under which the missile is stopped in tissue or chances to pass through. The greater the quantity of energy available for release, the greater the potential for damage; and the shorter the time span over which the energy is deposited or transferred, the more like an explosion it becomes. The amount of energy theoretically available has been derived from a several possible constructions relating E, M, and V, including momentum (MV), kinetic energy (l/2 MV2), and power (0~MV3). Each of these expressions places a different emphasis on velocity. There are historical reasons why certain constructions were invoked on specific occasions to justify some detail of firearm or ammunition design. At the turn of the century, for example, the chamber pressures attainable in military weapons were limited by metallurgic considerations. Ballistic design came to be focused on massive bullets with relatively low velocity, similar to those used for hunting big game. Modem ammunition, in contrast, is no longer limited in any practical sense by the design of the weapon, so that it can attain tremendous energy by emphasizing velocity at the expense of mass. This ballistic design tends to make weapons cycle more easily and permits the foot soldier to carry a larger quantity of ammunition for the same weight. However, light bullets are easily deflected and their energy decays rapidly over distance. For these. reasons, there is continued reliance on slower and heavier bullets. In most NATO and Warsaw Pack armies, the low mass (55 grain), small caliber (.233), high-velocity bullets chosen for modem assault rifles are supplemented by slower, more massive rounds (for example, the 150 grain .308 or 7.62 caliber bullet) for sniper use. This is an important point, because sniper tactics emphasize aiming at the head, placing the medulla oblongata at the epicenter of the target area. Not all sniper attacks are intended to kill, however, because, from a political standpoint, the disablement of prominent persons is frequently more strategically demoralizing than their death. For this reason, whether intentionally or by chance, some high-velocity wounds will be survived. It is wise to shed any preconceived expectations regarding penetrating missile injuries. Recent experience has shown
that many weapons and rounds can be modified to deposit more energy than one might predict: Standard handgun ammunition can be hand-loaded to attain 1600 ft/sec; “hot” ammunition designed for submachine-gun use can be discharged in most 9-mm pistols, and cast bronze or teflon clad bullets produce unusual cavitation. Moreover, blast effects from exploding bullets, grenades, and incendiary devices in the urban setting create wounds that combine the worst characteristics of closed and penetrating head injury.” A missile’s energy is greatest at the moment at which it is launched, and decays with time and distance. A .30/30 caliber, 170 grain bullet can be discharged with a muzzle velocity of 2220 ft/sec, for example; at 100 yards, the velocity drops to 1350 ft/sec, and at 200 yards, to 1000 ft/sec, well in the range of handgun ammunition. Most survivable injuries occur at low impact velocity. From a practical standpoint, the terminal ballistic events-what happens when the bullet strikes tissuedetermines the quantity of energy released and the explosive force developed. These factors are more important than muzzle velocity or bullet mass. What counts is the striking, or impact energy, rather than the muzzle velocity, because the amount of energy imparted to tissue when a projectile strikes is limited by the energy at impact. As a rule, more energy is imparted by penetrating injuries than by perforating (through-and-through) injuries. Penetrating missiles deposit all their energy in tissue, whereas perforating missiles retain sufficient energy to exit the body. The difference between the energy at impact and the residual energy at exit determines the energy delivered. The perfect bullet would release all of its energy instantaneously: dE/dt (t = time) would be infinite. Modem ballistic design, therefore, strives for smooth, friction-free flight in air, but infinite resistance in tissue. This goal is achieved by physical changes in the shape or ballistic characteristics of the bullet in tissue. The sudden loss of spin, for example, has two major effects: First, a significant quantity of angular energy is released; second, the bullet destabilizes, slows, tumbles, and sometimes fragments. Even a glancing, tangential injury can generate significant injury because of the energy transmitted to adjacent structures. ‘2.‘3On the other hand, clothing and other haphazard factors that impede the flight of a missile can reduce the energy deposited. In civilian life, most injuries occur at less than 50 yards, so that impact velocity can be assumed to equal to muzzle velocity. The distance at which a soldier is shot in wartime is rarely known. This variable helps account for survival after ostensibly high-energy bullet wounds. PATHOPHYSIOLOGY Cushing classified wounds of the head into nine categories according to severity and appearance. These proved significant predictors of outcome in World War I (Table l).’ Matson’s classification (Table 2) reflects clinically signifi141
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TABLE1. The Earliest Classification of Bullet Wounds to the Head with Prognostic Significance* Grade I II Ill IV V VI
VII VIII IX
Description Scalp disruption, intact calvarium and dura, possible cerebral contusion Fractured skull, dura intact, with or without depression of outer table Focally depressed skull fracture, dura lacerated Gutter fracture, indriven fragments Penetrating wounds with indriven fragments Ventricular penetration with bone fragments (A) projectile (6) Complex wounds involving nasopharynx, ear, or orbit Perforating (through-and-through) wounds Craniocerebral injury with massive skull fracture
Mortality (%) 4.5
4 Collapse of the temporary cavity leaving a residual permanent cavity, the bullet track, with an area of surrounding tissue damage. 5 Extravasation of blood around the missile track, occupying a space larger than, but fairly concentric with, the temporary cavity.
9.2 11.8 24.0 36.6
42.8 100.0 73.3 80.0 50.0
*Gushing H. A study of a series of wounds involving the brain and its enveloping structures. Br J Surg 1918;6:558-664.
cant observations during World War II.3 Advances in neuroradiology, however, especially since the widespread availability of CT, have indicated that such gross descriptions have less prognostic value than was previously believed because the extent of internal injury is not accurately reflected by the external manifestations. Harvey and associates’4 gave the classic account of the five events that accompany bullet penetration: 1 Shock waves at an angle to the bullet path. 2 A temporary cavity lasting approximately 20 msec as energy is transferred to the tissue. 3 Pulsation of the temporary cavity before it collapses, sending pressure waves through adjacent tissue and causing remote injury and hemiation.
Natureof the Bullet Track The relationship of the permanent cavity to muzzle velocity is fairly constant at distant, but not at close range. A high-velocity bullet creates a beet-shaped cavity, and a lowvelocity bullet creates a carrot-shaped cavity. The exit wound is always larger than the entrance wound in long-range, but not short-range perforating injuries. The cavitary effect of low-velocity missiles is inconsistent, and determined by both the direction of travel and extent of yaw. High-velocity missiles, in general, create a more consistent cavity. Specific cavitary characteristics cannot be projected for fragmenting missles because the configuration is a function of the complexities of energy transfer. I5 Bone Chips Bone chips from the skull, accompany, and at times outline, the penetration trajectory in the brain and may be thrown off by tangential (nonpenetrating) injuries as well. I6 The bullet path can often be determined on plain skull films by the track of bone chips. Bone chips occasionally form a secondary track, but the volume of this tract is usually small. Bone chips rarely act as secondary missiles of any significance. The volume of residual chips on plain skull films after surgery has been traditionally regarded as a measure of the adequacy of debridement.’ to such an extent that prophylactic reoperation would be recommended for retained bone fragments in order to prevent infection. Data from the VHIS, however, indicates that it is impossible to remove all bone chips from a wound if CT, rather than plain films is used as the radiographic control.
TABLE2. Matson’s Classification* I. Scalp laceration II. Compound linear and depressed fracture without dural penetration Ill. Compound fracture with penetration of dura and brain A. Gutter type, bone fragments but no metal fragments driven into brain B. Penetrating wounds: missile retained in brain C. Perforating (through-and-through) wounds IV. Complicating factors A. Ventricular involvement B. Orbit or sinus fracture C. Dural sinus injury D. lntraparenchymal hematoma ‘Matson DD. The Treatment of Acute Craniocerebral Injuries Due to Missiles. Springfield, Illinois, Charles C. Thomas, 1948.
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Acute Bursts of ICP Signs of acute bursts of intracranial pressure (ICP) accompany 90% of fatal head injuries. The significance of these pressure marks is controversial.18-20 The degree of ICP does not correlate directly with missile velocity, cavity size, or duration of survival. Bursts of ICP are not the same as cerebral edema: Despite the prevalence of brain markings indicating ICP bursts, only 33% of patients who die of bullet wounds show cerebral edema; on the other hand, massively swollen brains, perhaps reflecting a hyperacute hyperemia, have been described in patients surviving only a few minutes. Low-velocity wounds observed in civilian practice have not been consistently associated with cerebral edema
DAGI W MISSILE INJURIES TO THE BRAIN
unless the brainstem is traversed. In the Israeli experience, one of the points of differentiation between blast effects and simple penetrating injuries was the impressive degree of treatable ICP rise in blast injuries (Moshe Feinsod, MD, personal communication). Contusionsand Hematomas Cortical contusions are present at the site of entry in 50% of patients, and at the site of exit or at a point of contrecoup in addition to or instead of in another 50%. Irrespective of
bullet path, subfrontal contusions are found in 25% of patients. Other remote contusions are also commonly found. I6 CT scan data from the VHIS substantiates the long-standing clinical impression that the degree of actual injury far surpasses any gross estimate. It is also likely that CT obtained close to the time of injury will in the future demonstrate a higher prevalence of hematoma than heretofore supposed. Whether or not this will have clinical significance remains to be ascertained. During the Korean War, 46.2% of patients seen within eight hours of injury had intracranial hematomas; this figure
FIGURE I (top). Computed tomographic (CT) scans of the brain following self-inflicted, transventricular .22 caliber through-and-through wound at point blank range. The entrance wound is on the right (R). The patient was comatose and decerebrate with midposition reactive pupils and spontaneous respiratory efforts. Blood pressure and pulse were normal. The CT scans were obtained within 30 to 45 minutes of injury. The bullet track is shown at the level of entry (a) and, at the next higher cut (b), extending contralaterally toward the level of exit. Note that the size of the hematoma at the site of entry (arrow) is larger than the hematoma at the site of exit. Conventional wisdom dictates that the exit wound is more severe, and the hematoma at the site of exit is larger. Although this is generally true with very high velocity rifle wounds, it need not always be the case. FIGURE 2 (bottom). Immediate postoperative scans. A separate craniotomy was performed on each side of the head. The entrance wound (a) was decompressed first. Immediately on opening the calvarium, the clot delivered itself, and the brian, now decompressed, began to pulsate. The residual bullet track (a and b, arrow) is clearly visualized. Despite a thorough debridement, some retained fragments are evident (arrowheads). Before computed tomography, the exit wound probably would have been explored first, and the clot might not have been decompressed in time to save this patient’s life. Here, the entrance wound was more severe. This is a good example of why CT scan is now a prerequisite for treating penetrating missile injuries, and why precomputed tomography era studies must be viewed with a certain degree of skepticism.
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dropped to 27% after 12 to 35 hours, and 7% after 48 to 72 hours.21 In all likelihood, this trend is apparent rather than real and is a function of who survived to be seen at 72 hours. Thus, in a civilian series, hematomas were found in 44% of patients seen within 5.5 hours of injury.17 The distribution of clots is also variable. In 316 patients seen within 8 hours of wounding, 3% of clots were extradUral, 21% subdural, 23% intracerebral, and 0.2% intraventricular. Multiple hematomata are quite common. I9 In military practice, hematomas at the site of exit have been thought to be more physiologically and anatomically significant with respect to tissue destruction and functional impairment than those elsewhere in the brain. 22This is not the case in civilian wounds (Fig. 1).
Fracturesand Fracture Lines Fracture lines that accompany gunshot wounds to the brain tend to pass from the point of impact to the opposite pole, sparing or shifting directions at buttress lines. Shock waves within the skull cause fractures of the orbital roofs and cribiform plate even when the missile proceeds elsewhere. I6 This helps to explain why cerebrospinal leaks after penetrating missile injuries are common and, in equal measure, recalcitrant to treatment. The leptomeninges are typically lacerated by fracture lines at multiple, widely separated locations.
Tangential Injuries Tangential injuries are common among survivors. Although they have a significant morbidity, they carry the best prognosis of all types of missile injuries. In the pre-CT era, it was estimated that 75% of survivors would have significant cortical contusions,subcortical hematomas, subdural hematomas, and/or venous sinus disruption. Comparable data have not been elicited using current diagnostic techniques.
Blast Injuries In urban battle, blast injuries complicate penetrating trauma with forces akin to those encountered in “pure” closed head injury of the more familiar acceleration/deceleration variety. This type of injury was characteristic of patients who were evacuated from the Lebanon conflict and had, as the major pathophysiologic component, a rapid and diffuse increase in intracranial pressure. It can be presumed that this type of injury will also be a factor with penetrating fragment wounds from grenades and terrorist explosive devices and from exploding bullets.
between injury and definitive treatment. Whereas the disruption of tissue caused by passage of the bullet cannot be surgically repaired, some of the more serious sequelae of craniocerebral trauma, including uncontrolled rise of ICP, infection, and delayed hemorrhage, can be minimized by effective management. In the Israeli experience, physicians accompanying helicopter evacuation teams made significant gains by resuscitating patients on the ground before removal, and in flight. Resuscitation cannot be begun too early! There are 10 steps to the initial management of the wounded: 1. Resuscitation: An airway is secured. In addition to the usual candidates for intubation, all patients without purposeful motor responses are intubated and hyperventilated. Blood pressure is maintained. Hypotension may be a function of profound, and probably fatal, cerebral damage, but it can also occur as a consequence of scalp injury, venous sinus disruption, and complex injuries involving the abdomen, thorax, and lung. Restoration of normal blood volume is essential to the maintenance of cerebral perfusion. Furthermore, the neurologic examination has no prognostic significance until cerebral perfusion and oxygenation has been achieved. Massive cerebral injury is frequently accompanied by coagulopathies. Artificial plasma expanders, whole blood and fresh frozen plasma are administered. 2. Clothing is removed. 3. The patient is examined for entrance and exit wounds and other injuries elsewhere in the body. 4. A thorough neurologic examination is performed and documented. This evaluation can be very rapid but still provide sufficient information to locate the patient on the Glasgow coma scale. Recording the coma score does not eliminate the need for describing the examination in detail, because the nature of any localizing or lateralizing neurologic signs has both diagnostic and prognostic significance. Several serial examinations usually are referable to a single detailed evaluation. 5. There is no evidence that corticosteroids are helpful in reducing morbidity. There use is not indicated. Administration of mannitol, 0.5 to 1 gm/kg, on the other hand, should be initiated together with hyperventilation in order to control intracranial pressure. Mannitol should not be used in the presence of significant hypotension.
MANAGEMENT
6. Antibiotics are begun. Semisynthetic penicillins are supplemented by other antibiotics as determined by local conditions in wartime.
Morbidity and mortality can be reduced by improving the quality of initial resuscitation and minimizing the interval
7. The head is shaved, and potentially scalp bleeding is controlled.
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exanguinating
DAGI n MISSILE INJURIES TO THE BRAIN
8. X-ray studies, including plain skull films, cervical spine films, and CT scan of the brian, are obtained. The scout view on the CT scan can, in many instances, render the plain skull film superfluous as a necessary prerequisite. 9. ICP monitoring may be useful. 10. Intensive care is initiated while waiting for operation or when immediate operation is unnecessary. All patients should undergo immediate neuroimaging studies with two possible exceptions: Patients deteriorating rapidly may be candidates for immediate exploration, where the source of worsening is thought to be a hematoma and where an unacceptable delay is anticipated before CT can be obtained; and patients with multiple injury where laparotomy or thoracotomy is needed for control of life-threatening hemorrhage. In this second situation, it will often be necessary to perform an exploratory craniotomy in conjunction with other operative procedures. Until recently, air or bone chips in the missile track were relied on to indicate the bullet path. These, together with clumps of bone and fragments of metal, served to direct the intracranial exploration. Today, CT scanning has supplanted this function. Except under the most primitive situations, CT scanning should be available wherever a neurosurgeon operates. Even complex patterns of skull injury are better shown on CT (using bone windows) than on plain radiographs, and this certainly holds true for combined facial, orbital, sinus, and cranial wounds. The role of angiography is controversial. Although angiography is no longer the primary modality of choice in evaluating mass effects and shifts within the brain, there is a definable incidence of traumatic vascular injury not visible on CT. Traumatic aneurysms can enlarge and bleed. There is no comprehensive estimate of the likelihood of this phenomenon. Where missile paths approach major arterial structures, angiography is probably desirable before discharge. Shotgun injuries and fragmenting bullets may create a higher risk of traumatic aneurysm than other types. Certainly, any delayed hematoma should be evaluated angiographically.
TRIAGE There is a logical order that should be followed in mass casualty situations. Active and potentially exanguinating hemorrhage is dealt with first. Patients who are awake and alert, or those with focal deficits are treated second. Comatose patients, particularly those with through-and-through injuries are seen next. Obviously, moribund patients are left for last. Some very important caveats must be observed.
1. Triage is only carried out when the number of casualties surpasses the ability of a facility to treat them simultaneously. 2. If at all possible, it is best to coordinate evaculation centrally and to divert patients to various facilities en route so that every patient can get the necessary care. 3. Neurologic assessment cannot be made until after resuscitation has been successfully accomplished. 4. The most senior, most experienced person should be responsible for the triage in the emergency room. Neurologic injuries require that a neurosurgeon carry out the triage when at all possible. 5. The need for pressing triage decisions can often be mitigated by drafting additional personnel from specialities not ordinarily involved in emergency procedures (pediatricians to start intravenous infusions, gynecologists to perform cut-downs, neurologists to carry out detailed neurologic examinations). 6. Although the initial neurologic presentation has important prognostic significance in penetrating head injuries, an astounding degree of recovery is possible .
7. Triage decisions based on estimates of likelihood of survival are often self-fulfilling prophecies. 8. Philosophical “do not resuscitate” decisions are out of place in the emergency department.
SURGICALCONSIDERATIONS A full discussion of surgery for penetrating missile injuries cannot be accomplished in this review but is available elsewhere.23 In brief, there are four purposes to surgery: Life-saving reduction of mass; prevention of infection; preservation of function; and restoration of anatomic structures. Several general observations regarding surgery can be made. It is necessary to inspect and debride each layer of the wound separately. The first operation should be definitive whenever possible. The scalp heals remarkably well; only devitalized tissue should be excised. Muscle, on the other hand, often serves as a nidus for infection and needs to be debrided vigorously. The skull and brain must be covered by viable tissue. If necessary, skin grafts or myocutaneous flaps can be used at the time of initial surgery: the skin does not heal well under tension. Complex injuries involving the orbit or the air sinuses must also be treated with a definitive approach in mind at the time of first exploration. This is not meant to imply that later operations for cosmetic or functional repair may not be necessary, but rather that, attitudinal/y, the first operation should be definitive. 145
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PROGNOSIS
TABLE3. Outcome after Civilian Penetrating Injury* Stage I
II Ill IV
V
Description Alert, no loss of consciousness or neurologic deficit, hematoma excluded angiographically Same, but with focal deficit Somnolent, agitated, or confused; documented loss of consciousness Comatose, responsive to pain, tracheostomy (mortality reduced to 50% in those who underwent operation) Comatose and posturing
Mortality (%) 0
0 35 75
100
‘Raimondi AS, Samuelson GH: Craniocerebral gunshot wounds in civilian practice. J Neurosurg 1970; 32:647-653.
Once the brain has been exposed by craniectomy, active bleeding is stopped, clots are evacuated, and devitalized tissue along the missile track is debrided. In the swollen brain, the evacuation of even a small amount of contused, hemorrhagic brain can make the difference between marginal compliance and fatal intracranial hypertension (Fig. 2). Contaminated bone fragments are pursued within reason. Metal fragments are also pursued, but not as vigorously as bone, and certainly not at the risk of neurologic deficit. The dura is closed, incorporating a dural graft where needed. Watertight closure is of special importance when the air sinuses are disrupted and the risk of meningitis with cerebrospinal fluid leak is high. Only rarely does a bullet wound affect the scalp alone. Additional, occult injuries must be suspected whenever the scalp is injured. A CT scan is mandatory for all tangenital and “grazing” injuries. Entrance and exit wounds often require separate incisions. The exit wound is traditionally held to be the site of the most severe damage and, therefore, the site of primary exploration. Low-velocity injuries do not necessarily follow this rule. CT scan remains the best modality by which to make operative decisions. Transventricular wounds are particularly devastating. Hydrocephalus and delayed hematomata are frequent complications. Foreign bodies in the ventricle are best left behind unless they are readily accessible. They can be removed secondarily if necessary. Ventricular injuries frequently give rise to unexplained cyclical fevers and endocrine abnormalities. When patients are operated on within 12 hours of the injury, many tracks and most bone chips are sterile. When treatment is delayed, secondary contamination occurs. Any single individual bone fragment is probably sterile, but each track is likely to include fragments of contaminated bone. Metal fragments, on the other hand, rarely become foci of infection.
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A number of anatomic and neurologic observations have been found to carry important prognostic implications. In pre-CT series, disruption of more than one third of the ventricular wall was invariably fatal. The syndrome of coma, fixed dilated pupils, Cheyne-Stokes respirations, and spastic quadraparesis or flaccidity was thought by Matson to be incompatible with recovery in a wartime setting. Raimondi and Samuelson assigned patients to one of five categories according to neurologic status on admission (Table 3).19 Patients who were alert and who had never lost consciousness (group I) or who had a focal deficit only (group II) invariably survived. Somnolence, agitation, or confusion following loss of consciousness (group III) was associated with a 35% mortality. Obtundation with response to voice or pain, or coma without abnormal motor posturing (group IV) had an associated mortality of 75%. Coma with posturing (group V) was not survived. Bymes et al.6 related outcome to consciousness and vital signs on admission. No patient in deep coma survived. Only 4% of those with fixed and dilated pupils survived. Less than 25% of patients responsive to deep pain only survived. Those who were alert, slightly drowsy, reactive pupils almost always survived. Similar data were amassed by Carey et al. in Vietnam.*” CrockardZ5 examined head-injured patients in Belfast within 20 minutes of wounding. ICP proved ineffective as a prognostic measure. Arterial hypertension, in contrast, proved highly significant: Hypertension above 160 systolic carried a 93% morbidity. One important question arises in all pre-CT scan studies: could the prognosis have been improved by the evacuation of accessible hematomas that were missed, or was the examination on presentation prognostically valid regardless of other considerations? In the only major study using CT to eliminate the possibility of major space-occupying lesions, Hubschmann et aLZ6 demonstrated that the level of alertness and other neurologic signs accurately correlated with functional outcome (Table 4).
OUTCOME Over the past 30 years, one thing has become increasingly clear: although the survival after penetrating missile injuries can be improved by the measures just discussed, functional recovery is in many cases worse than what might have been traditionally predicted. So sensitive is the brain to high energy forces from penetrating missiles that careful neuropsychological evaluation of the type carried out by the VHIS has successfully demonstrated subtle but consistent deficits even in the absence of major tissue loss. No study has documented the long-term outcome of missile injuries in a civilian population.
DAGI n MISSILE INJURIES TO THE BRAIN
TABLE4. Functional Outcome*
Grade I II Ill IV
Total
Outcome
Findings on Admission
Total
Patients Undergoing Operation
Alert, awake Obtunded, with or without focal deficit Responsive to noxious stimuli only Comatose, posturing 39 or no response to noxious stimuli after resuscitation
14 21
13 19
14 16
0 2
0 3
8
7
2
2
4
39
6
0
0
39
82
45
32
4
48
Functional
Nonlunctional
Died
Key: Functional: intact, or with focal deficit, but independent; Nonfunctional: severe deficit preventing independent function or requiring institutional care. lHubschmann 0, Shapiro K, Baden M, et al. Craniocerebral gunshot injuries in civilian practice-prognostic criteria and surgical management: Experience with 82 cases. J Trauma 1979; 196-12.
The well-known long-term sequelae of penetrating injuries include recurring and delayed infection, sometimes as long as 25 or 30 years after injury, and seizure disorders. There is nothing that can be done in the emergency setting, preoperatively, to affect the incidence of these problems. Surgical technique can have a limited, albeit a definite influence on long-term outcome. It is important to remember, however, that when a patient with a history of penetrating missile injury presents with an acute neurological event, a correlation between the two must be rule out. CONCLUSION Penetrating injuries of the head need not be invariably fatal. Through careful resuscitation, thorough search for operable lesions, and meticulous surgical technique, almost every patient who is not in a coma should survive. A satisfying functional recovery can be achieved by attention to the details of resuscitation and initial assessment.
REFERENCES 1. Cushing H. A study of a series of wounds involving the brain and its enveloping structures. Br J Surg 1918;8:558-684 2. Meirowsky AM (ed). Neurological Surgery of Trauma. Washington, DC, Office of the Surgeon General, 1964 3. Matson DD. The Treatment of Acute Craniocerebral Injuries due to Missiles. Springfield, Illinois, Charles C. Thomas, 1948 4. British Journal of Surgery. War Surgical Supplement, 1947 5. Lewin W, Gibon MR. Missile head wounds in the Korean campaign: A survey of British casualkies. Br J Surg 1956;43:628-632 6. Byrnes DP, Crockard HA, Gordon DS, et al. Penetrating craniocerebral missile injuries in the civil disturbances in Northern Ireland. Br J Surg 1971;61:169-176
7. Meyers PW, Salazar AM. Vietnam Head Injury Study: Combatcaused penetraitng head wounds-assessment 14 years after injury. Presented in part April 27, 1986, Course 104, Annual Meeting, American Academy of Neurology. (Manuscript in preparation) 8. Markush RE, Bartolucci AA. Firearms and suicide in the United States. Am J Public Health 1984;74:123-127 9. Demuth WE Jr. Bullet velocity as applied to military rifle wounding capacity. J Trauma 1969;9:27-32 10. Demuth WE Jr. Bullet velocity and deisng as determinants of wounding capability. An experimental study. J Trauma 1986;6:222-232 11. Dobbyn RC, Bruckly WL Jr, Shubin LD. An Evaluation of Police Handgun Ammunition: Summary Report. Washington DC US Department of Justice, 1975 12. Dodge PR, Meirowsky AM. Tangential wounds of the scalp and skull. J Neurosurg 1952;9:472-483 13. Adelola A, Odehus EL, A syndrome characteristic of tangential bullet wounds of the vertex of the skull. J Neurosurg 1971;34:155-158 14. Harvey EW, Butler EG, McMillen JH, et al. Mechanisms of wounding. War Med 1945;8:91-104 15. Kirpatrick JB, DiMaio VD. Civilian gunshot wounds of the brain. J Neurosurg 1978;49:185-198 16. Meirowsky AM. Secondary removal of retained bone fragments in missile wounds of the brain. J Neurosurg 1982;57:617-621 17. Harmon WM. Retained intracranial bone fragments: Analysis of 42 patients. J Neurosurg 1971;34:142-154 18. Freytag E. Autopsy findings in head injuries from firearms: Statistical evaluation of 254 cases. Arch Pathol 1983;76:215-225 19. Raimondi AS, Samuelson GH: Craniocerebral gunshot wounds in civilian practice. J Neurosurg 1970;32:647-853 20. Crockard HA. Bullet injuries of the brain. Ann Coll Surg Engl 1974;55:111-123 21. Barnett JC, Meirowsky AM. Intracranial hematoma associated with penetrating wounds of the brain. J Neurosurg 1955;12:34-48 22. Matson DD, Wolkin J. Hematoma associated with penetrating wounds of the brain. J Neurosurg 1946;3:46-53
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23. George ED, Dagi TF. Penetrating missile injuries of the head. ln Schmidek H, Sweet WH (eds). Operative Neurosurgery, ed 2. New York, Grune and Stratton. In press 24. Carey ME, Young H, Mathis JL. The neurosurgical treatment of craniocerebral missile wounds in Vietnam. Surg Gynecol Obstet 1972;135:386-390
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25. Crockard HA. Early intracranial pressure studies in gunshot wounds of the brain. J Trauma 1975;15:339-347 26. Hubschmann 0, Shapiro K, Baden M, et al. Craniocerebral gunshot injuries in civilian practice-prognostic criteria and surgical management: Experience with 82 cases. J Trauma 1979;19:6-12
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Words: Gunshot wound, head injury, resuscitation.
the National Institutes of Health, was established to register and study outcome after penetrating head injury. The VHIS has followed a large population using sophisticated epidemiologic, radiologic, and neuropsychologic techniques for more than 18 years. A great deal of data that was lost in the past, when injured veterans were not aggressively followed beyond discharge from the hospital, is now being collected and studied.’ A number of recurring concerns characterize the literature on penetrating missile injuries of the brain: 1. The practical significance of distinguishing between high velocity and low velocity wounds. 2. The importance the wounded.
of early transport and treatment of
3. The definition of what constitutes gical debridement.
adequate
sur-
4. Specific methods of dealing with complex wounds involving the orbit, the air sinuses, and major vascular structures. 5. The management
of cerebrospinal
fluid fistulas.
6. The prevention and diagnosis of acute infection, of delayed abcess, and of hematoma. 7. The epidemiology seizure disorders.
and prevention
of posttraumatic
More recently, the epidemiologic and preventive medicine literature has reflected an increasing sensitivity to the issue of firearm injuries as a problem of public health.8 Because of the evidence that initial resuscitation and evacuation play a crucial role in the ultimate outcome of penetrating missile injuries of the brain, it is important that those involved in emergency medicine be aware of recent developments in the management of these injuries. This review will focus on these developments and, more briefly, on evolving concepts in ballistics and pathophysiology, in surgical technique, and in prognosis. These subjects are particularly important in view of terrorist attacks that have threatened populated urban centers with unfamiliar battlefield injuries. TERMINAL BALLISTICS: DETERMINANTSOF THE DEGREE OF INJURY
Injury to the brain is a function of the quantity of energy release over time; this is reflected in the volume and location of tissue damage. The traditional approach divides pene-
DAGI n MISSILE INJURIES TO THE BRAIN
trating missile injuries into high- and low-velocity categories, associating the severity of the wound with the muzzle velocity, mass, and calculated energy content of the missle.9.‘0 By convention, high velocity exceeds 2000 ft/sec. Most modern high-velocity rifle bullets easily surpass 2500 ft/sec. Most handgun ammunition ranges in velocity between 800 ft/sec and 1400 ft/sec. Typical penetrating fragments or shrapnel, in contrast, are estimated to strike at a velocity of 600 ft/sec or less. Most survivable penetrating cerebral injuries in war are caused by shrapnel or other fragments with attenuated or decayed energy levels. The energy (E) released in tissue depends in part on the missile mass (M) and velocity (V) at time of impact, and in part on the conditions under which the missile is stopped in tissue or chances to pass through. The greater the quantity of energy available for release, the greater the potential for damage; and the shorter the time span over which the energy is deposited or transferred, the more like an explosion it becomes. The amount of energy theoretically available has been derived from a several possible constructions relating E, M, and V, including momentum (MV), kinetic energy (l/2 MV2), and power (0~MV3). Each of these expressions places a different emphasis on velocity. There are historical reasons why certain constructions were invoked on specific occasions to justify some detail of firearm or ammunition design. At the turn of the century, for example, the chamber pressures attainable in military weapons were limited by metallurgic considerations. Ballistic design came to be focused on massive bullets with relatively low velocity, similar to those used for hunting big game. Modem ammunition, in contrast, is no longer limited in any practical sense by the design of the weapon, so that it can attain tremendous energy by emphasizing velocity at the expense of mass. This ballistic design tends to make weapons cycle more easily and permits the foot soldier to carry a larger quantity of ammunition for the same weight. However, light bullets are easily deflected and their energy decays rapidly over distance. For these. reasons, there is continued reliance on slower and heavier bullets. In most NATO and Warsaw Pack armies, the low mass (55 grain), small caliber (.233), high-velocity bullets chosen for modem assault rifles are supplemented by slower, more massive rounds (for example, the 150 grain .308 or 7.62 caliber bullet) for sniper use. This is an important point, because sniper tactics emphasize aiming at the head, placing the medulla oblongata at the epicenter of the target area. Not all sniper attacks are intended to kill, however, because, from a political standpoint, the disablement of prominent persons is frequently more strategically demoralizing than their death. For this reason, whether intentionally or by chance, some high-velocity wounds will be survived. It is wise to shed any preconceived expectations regarding penetrating missile injuries. Recent experience has shown
that many weapons and rounds can be modified to deposit more energy than one might predict: Standard handgun ammunition can be hand-loaded to attain 1600 ft/sec; “hot” ammunition designed for submachine-gun use can be discharged in most 9-mm pistols, and cast bronze or teflon clad bullets produce unusual cavitation. Moreover, blast effects from exploding bullets, grenades, and incendiary devices in the urban setting create wounds that combine the worst characteristics of closed and penetrating head injury.” A missile’s energy is greatest at the moment at which it is launched, and decays with time and distance. A .30/30 caliber, 170 grain bullet can be discharged with a muzzle velocity of 2220 ft/sec, for example; at 100 yards, the velocity drops to 1350 ft/sec, and at 200 yards, to 1000 ft/sec, well in the range of handgun ammunition. Most survivable injuries occur at low impact velocity. From a practical standpoint, the terminal ballistic events-what happens when the bullet strikes tissuedetermines the quantity of energy released and the explosive force developed. These factors are more important than muzzle velocity or bullet mass. What counts is the striking, or impact energy, rather than the muzzle velocity, because the amount of energy imparted to tissue when a projectile strikes is limited by the energy at impact. As a rule, more energy is imparted by penetrating injuries than by perforating (through-and-through) injuries. Penetrating missiles deposit all their energy in tissue, whereas perforating missiles retain sufficient energy to exit the body. The difference between the energy at impact and the residual energy at exit determines the energy delivered. The perfect bullet would release all of its energy instantaneously: dE/dt (t = time) would be infinite. Modem ballistic design, therefore, strives for smooth, friction-free flight in air, but infinite resistance in tissue. This goal is achieved by physical changes in the shape or ballistic characteristics of the bullet in tissue. The sudden loss of spin, for example, has two major effects: First, a significant quantity of angular energy is released; second, the bullet destabilizes, slows, tumbles, and sometimes fragments. Even a glancing, tangential injury can generate significant injury because of the energy transmitted to adjacent structures. ‘2.‘3On the other hand, clothing and other haphazard factors that impede the flight of a missile can reduce the energy deposited. In civilian life, most injuries occur at less than 50 yards, so that impact velocity can be assumed to equal to muzzle velocity. The distance at which a soldier is shot in wartime is rarely known. This variable helps account for survival after ostensibly high-energy bullet wounds. PATHOPHYSIOLOGY Cushing classified wounds of the head into nine categories according to severity and appearance. These proved significant predictors of outcome in World War I (Table l).’ Matson’s classification (Table 2) reflects clinically signifi141
AMERICAN JOURNAL OF EMERGENCY MEDICINE n Volume 5, Number 2 n March 1987
TABLE1. The Earliest Classification of Bullet Wounds to the Head with Prognostic Significance* Grade I II Ill IV V VI
VII VIII IX
Description Scalp disruption, intact calvarium and dura, possible cerebral contusion Fractured skull, dura intact, with or without depression of outer table Focally depressed skull fracture, dura lacerated Gutter fracture, indriven fragments Penetrating wounds with indriven fragments Ventricular penetration with bone fragments (A) projectile (6) Complex wounds involving nasopharynx, ear, or orbit Perforating (through-and-through) wounds Craniocerebral injury with massive skull fracture
Mortality (%) 4.5
4 Collapse of the temporary cavity leaving a residual permanent cavity, the bullet track, with an area of surrounding tissue damage. 5 Extravasation of blood around the missile track, occupying a space larger than, but fairly concentric with, the temporary cavity.
9.2 11.8 24.0 36.6
42.8 100.0 73.3 80.0 50.0
*Gushing H. A study of a series of wounds involving the brain and its enveloping structures. Br J Surg 1918;6:558-664.
cant observations during World War II.3 Advances in neuroradiology, however, especially since the widespread availability of CT, have indicated that such gross descriptions have less prognostic value than was previously believed because the extent of internal injury is not accurately reflected by the external manifestations. Harvey and associates’4 gave the classic account of the five events that accompany bullet penetration: 1 Shock waves at an angle to the bullet path. 2 A temporary cavity lasting approximately 20 msec as energy is transferred to the tissue. 3 Pulsation of the temporary cavity before it collapses, sending pressure waves through adjacent tissue and causing remote injury and hemiation.
Natureof the Bullet Track The relationship of the permanent cavity to muzzle velocity is fairly constant at distant, but not at close range. A high-velocity bullet creates a beet-shaped cavity, and a lowvelocity bullet creates a carrot-shaped cavity. The exit wound is always larger than the entrance wound in long-range, but not short-range perforating injuries. The cavitary effect of low-velocity missiles is inconsistent, and determined by both the direction of travel and extent of yaw. High-velocity missiles, in general, create a more consistent cavity. Specific cavitary characteristics cannot be projected for fragmenting missles because the configuration is a function of the complexities of energy transfer. I5 Bone Chips Bone chips from the skull, accompany, and at times outline, the penetration trajectory in the brain and may be thrown off by tangential (nonpenetrating) injuries as well. I6 The bullet path can often be determined on plain skull films by the track of bone chips. Bone chips occasionally form a secondary track, but the volume of this tract is usually small. Bone chips rarely act as secondary missiles of any significance. The volume of residual chips on plain skull films after surgery has been traditionally regarded as a measure of the adequacy of debridement.’ to such an extent that prophylactic reoperation would be recommended for retained bone fragments in order to prevent infection. Data from the VHIS, however, indicates that it is impossible to remove all bone chips from a wound if CT, rather than plain films is used as the radiographic control.
TABLE2. Matson’s Classification* I. Scalp laceration II. Compound linear and depressed fracture without dural penetration Ill. Compound fracture with penetration of dura and brain A. Gutter type, bone fragments but no metal fragments driven into brain B. Penetrating wounds: missile retained in brain C. Perforating (through-and-through) wounds IV. Complicating factors A. Ventricular involvement B. Orbit or sinus fracture C. Dural sinus injury D. lntraparenchymal hematoma ‘Matson DD. The Treatment of Acute Craniocerebral Injuries Due to Missiles. Springfield, Illinois, Charles C. Thomas, 1948.
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Acute Bursts of ICP Signs of acute bursts of intracranial pressure (ICP) accompany 90% of fatal head injuries. The significance of these pressure marks is controversial.18-20 The degree of ICP does not correlate directly with missile velocity, cavity size, or duration of survival. Bursts of ICP are not the same as cerebral edema: Despite the prevalence of brain markings indicating ICP bursts, only 33% of patients who die of bullet wounds show cerebral edema; on the other hand, massively swollen brains, perhaps reflecting a hyperacute hyperemia, have been described in patients surviving only a few minutes. Low-velocity wounds observed in civilian practice have not been consistently associated with cerebral edema
DAGI W MISSILE INJURIES TO THE BRAIN
unless the brainstem is traversed. In the Israeli experience, one of the points of differentiation between blast effects and simple penetrating injuries was the impressive degree of treatable ICP rise in blast injuries (Moshe Feinsod, MD, personal communication). Contusionsand Hematomas Cortical contusions are present at the site of entry in 50% of patients, and at the site of exit or at a point of contrecoup in addition to or instead of in another 50%. Irrespective of
bullet path, subfrontal contusions are found in 25% of patients. Other remote contusions are also commonly found. I6 CT scan data from the VHIS substantiates the long-standing clinical impression that the degree of actual injury far surpasses any gross estimate. It is also likely that CT obtained close to the time of injury will in the future demonstrate a higher prevalence of hematoma than heretofore supposed. Whether or not this will have clinical significance remains to be ascertained. During the Korean War, 46.2% of patients seen within eight hours of injury had intracranial hematomas; this figure
FIGURE I (top). Computed tomographic (CT) scans of the brain following self-inflicted, transventricular .22 caliber through-and-through wound at point blank range. The entrance wound is on the right (R). The patient was comatose and decerebrate with midposition reactive pupils and spontaneous respiratory efforts. Blood pressure and pulse were normal. The CT scans were obtained within 30 to 45 minutes of injury. The bullet track is shown at the level of entry (a) and, at the next higher cut (b), extending contralaterally toward the level of exit. Note that the size of the hematoma at the site of entry (arrow) is larger than the hematoma at the site of exit. Conventional wisdom dictates that the exit wound is more severe, and the hematoma at the site of exit is larger. Although this is generally true with very high velocity rifle wounds, it need not always be the case. FIGURE 2 (bottom). Immediate postoperative scans. A separate craniotomy was performed on each side of the head. The entrance wound (a) was decompressed first. Immediately on opening the calvarium, the clot delivered itself, and the brian, now decompressed, began to pulsate. The residual bullet track (a and b, arrow) is clearly visualized. Despite a thorough debridement, some retained fragments are evident (arrowheads). Before computed tomography, the exit wound probably would have been explored first, and the clot might not have been decompressed in time to save this patient’s life. Here, the entrance wound was more severe. This is a good example of why CT scan is now a prerequisite for treating penetrating missile injuries, and why precomputed tomography era studies must be viewed with a certain degree of skepticism.
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dropped to 27% after 12 to 35 hours, and 7% after 48 to 72 hours.21 In all likelihood, this trend is apparent rather than real and is a function of who survived to be seen at 72 hours. Thus, in a civilian series, hematomas were found in 44% of patients seen within 5.5 hours of injury.17 The distribution of clots is also variable. In 316 patients seen within 8 hours of wounding, 3% of clots were extradUral, 21% subdural, 23% intracerebral, and 0.2% intraventricular. Multiple hematomata are quite common. I9 In military practice, hematomas at the site of exit have been thought to be more physiologically and anatomically significant with respect to tissue destruction and functional impairment than those elsewhere in the brain. 22This is not the case in civilian wounds (Fig. 1).
Fracturesand Fracture Lines Fracture lines that accompany gunshot wounds to the brain tend to pass from the point of impact to the opposite pole, sparing or shifting directions at buttress lines. Shock waves within the skull cause fractures of the orbital roofs and cribiform plate even when the missile proceeds elsewhere. I6 This helps to explain why cerebrospinal leaks after penetrating missile injuries are common and, in equal measure, recalcitrant to treatment. The leptomeninges are typically lacerated by fracture lines at multiple, widely separated locations.
Tangential Injuries Tangential injuries are common among survivors. Although they have a significant morbidity, they carry the best prognosis of all types of missile injuries. In the pre-CT era, it was estimated that 75% of survivors would have significant cortical contusions,subcortical hematomas, subdural hematomas, and/or venous sinus disruption. Comparable data have not been elicited using current diagnostic techniques.
Blast Injuries In urban battle, blast injuries complicate penetrating trauma with forces akin to those encountered in “pure” closed head injury of the more familiar acceleration/deceleration variety. This type of injury was characteristic of patients who were evacuated from the Lebanon conflict and had, as the major pathophysiologic component, a rapid and diffuse increase in intracranial pressure. It can be presumed that this type of injury will also be a factor with penetrating fragment wounds from grenades and terrorist explosive devices and from exploding bullets.
between injury and definitive treatment. Whereas the disruption of tissue caused by passage of the bullet cannot be surgically repaired, some of the more serious sequelae of craniocerebral trauma, including uncontrolled rise of ICP, infection, and delayed hemorrhage, can be minimized by effective management. In the Israeli experience, physicians accompanying helicopter evacuation teams made significant gains by resuscitating patients on the ground before removal, and in flight. Resuscitation cannot be begun too early! There are 10 steps to the initial management of the wounded: 1. Resuscitation: An airway is secured. In addition to the usual candidates for intubation, all patients without purposeful motor responses are intubated and hyperventilated. Blood pressure is maintained. Hypotension may be a function of profound, and probably fatal, cerebral damage, but it can also occur as a consequence of scalp injury, venous sinus disruption, and complex injuries involving the abdomen, thorax, and lung. Restoration of normal blood volume is essential to the maintenance of cerebral perfusion. Furthermore, the neurologic examination has no prognostic significance until cerebral perfusion and oxygenation has been achieved. Massive cerebral injury is frequently accompanied by coagulopathies. Artificial plasma expanders, whole blood and fresh frozen plasma are administered. 2. Clothing is removed. 3. The patient is examined for entrance and exit wounds and other injuries elsewhere in the body. 4. A thorough neurologic examination is performed and documented. This evaluation can be very rapid but still provide sufficient information to locate the patient on the Glasgow coma scale. Recording the coma score does not eliminate the need for describing the examination in detail, because the nature of any localizing or lateralizing neurologic signs has both diagnostic and prognostic significance. Several serial examinations usually are referable to a single detailed evaluation. 5. There is no evidence that corticosteroids are helpful in reducing morbidity. There use is not indicated. Administration of mannitol, 0.5 to 1 gm/kg, on the other hand, should be initiated together with hyperventilation in order to control intracranial pressure. Mannitol should not be used in the presence of significant hypotension.
MANAGEMENT
6. Antibiotics are begun. Semisynthetic penicillins are supplemented by other antibiotics as determined by local conditions in wartime.
Morbidity and mortality can be reduced by improving the quality of initial resuscitation and minimizing the interval
7. The head is shaved, and potentially scalp bleeding is controlled.
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exanguinating
DAGI n MISSILE INJURIES TO THE BRAIN
8. X-ray studies, including plain skull films, cervical spine films, and CT scan of the brian, are obtained. The scout view on the CT scan can, in many instances, render the plain skull film superfluous as a necessary prerequisite. 9. ICP monitoring may be useful. 10. Intensive care is initiated while waiting for operation or when immediate operation is unnecessary. All patients should undergo immediate neuroimaging studies with two possible exceptions: Patients deteriorating rapidly may be candidates for immediate exploration, where the source of worsening is thought to be a hematoma and where an unacceptable delay is anticipated before CT can be obtained; and patients with multiple injury where laparotomy or thoracotomy is needed for control of life-threatening hemorrhage. In this second situation, it will often be necessary to perform an exploratory craniotomy in conjunction with other operative procedures. Until recently, air or bone chips in the missile track were relied on to indicate the bullet path. These, together with clumps of bone and fragments of metal, served to direct the intracranial exploration. Today, CT scanning has supplanted this function. Except under the most primitive situations, CT scanning should be available wherever a neurosurgeon operates. Even complex patterns of skull injury are better shown on CT (using bone windows) than on plain radiographs, and this certainly holds true for combined facial, orbital, sinus, and cranial wounds. The role of angiography is controversial. Although angiography is no longer the primary modality of choice in evaluating mass effects and shifts within the brain, there is a definable incidence of traumatic vascular injury not visible on CT. Traumatic aneurysms can enlarge and bleed. There is no comprehensive estimate of the likelihood of this phenomenon. Where missile paths approach major arterial structures, angiography is probably desirable before discharge. Shotgun injuries and fragmenting bullets may create a higher risk of traumatic aneurysm than other types. Certainly, any delayed hematoma should be evaluated angiographically.
TRIAGE There is a logical order that should be followed in mass casualty situations. Active and potentially exanguinating hemorrhage is dealt with first. Patients who are awake and alert, or those with focal deficits are treated second. Comatose patients, particularly those with through-and-through injuries are seen next. Obviously, moribund patients are left for last. Some very important caveats must be observed.
1. Triage is only carried out when the number of casualties surpasses the ability of a facility to treat them simultaneously. 2. If at all possible, it is best to coordinate evaculation centrally and to divert patients to various facilities en route so that every patient can get the necessary care. 3. Neurologic assessment cannot be made until after resuscitation has been successfully accomplished. 4. The most senior, most experienced person should be responsible for the triage in the emergency room. Neurologic injuries require that a neurosurgeon carry out the triage when at all possible. 5. The need for pressing triage decisions can often be mitigated by drafting additional personnel from specialities not ordinarily involved in emergency procedures (pediatricians to start intravenous infusions, gynecologists to perform cut-downs, neurologists to carry out detailed neurologic examinations). 6. Although the initial neurologic presentation has important prognostic significance in penetrating head injuries, an astounding degree of recovery is possible .
7. Triage decisions based on estimates of likelihood of survival are often self-fulfilling prophecies. 8. Philosophical “do not resuscitate” decisions are out of place in the emergency department.
SURGICALCONSIDERATIONS A full discussion of surgery for penetrating missile injuries cannot be accomplished in this review but is available elsewhere.23 In brief, there are four purposes to surgery: Life-saving reduction of mass; prevention of infection; preservation of function; and restoration of anatomic structures. Several general observations regarding surgery can be made. It is necessary to inspect and debride each layer of the wound separately. The first operation should be definitive whenever possible. The scalp heals remarkably well; only devitalized tissue should be excised. Muscle, on the other hand, often serves as a nidus for infection and needs to be debrided vigorously. The skull and brain must be covered by viable tissue. If necessary, skin grafts or myocutaneous flaps can be used at the time of initial surgery: the skin does not heal well under tension. Complex injuries involving the orbit or the air sinuses must also be treated with a definitive approach in mind at the time of first exploration. This is not meant to imply that later operations for cosmetic or functional repair may not be necessary, but rather that, attitudinal/y, the first operation should be definitive. 145
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PROGNOSIS
TABLE3. Outcome after Civilian Penetrating Injury* Stage I
II Ill IV
V
Description Alert, no loss of consciousness or neurologic deficit, hematoma excluded angiographically Same, but with focal deficit Somnolent, agitated, or confused; documented loss of consciousness Comatose, responsive to pain, tracheostomy (mortality reduced to 50% in those who underwent operation) Comatose and posturing
Mortality (%) 0
0 35 75
100
‘Raimondi AS, Samuelson GH: Craniocerebral gunshot wounds in civilian practice. J Neurosurg 1970; 32:647-653.
Once the brain has been exposed by craniectomy, active bleeding is stopped, clots are evacuated, and devitalized tissue along the missile track is debrided. In the swollen brain, the evacuation of even a small amount of contused, hemorrhagic brain can make the difference between marginal compliance and fatal intracranial hypertension (Fig. 2). Contaminated bone fragments are pursued within reason. Metal fragments are also pursued, but not as vigorously as bone, and certainly not at the risk of neurologic deficit. The dura is closed, incorporating a dural graft where needed. Watertight closure is of special importance when the air sinuses are disrupted and the risk of meningitis with cerebrospinal fluid leak is high. Only rarely does a bullet wound affect the scalp alone. Additional, occult injuries must be suspected whenever the scalp is injured. A CT scan is mandatory for all tangenital and “grazing” injuries. Entrance and exit wounds often require separate incisions. The exit wound is traditionally held to be the site of the most severe damage and, therefore, the site of primary exploration. Low-velocity injuries do not necessarily follow this rule. CT scan remains the best modality by which to make operative decisions. Transventricular wounds are particularly devastating. Hydrocephalus and delayed hematomata are frequent complications. Foreign bodies in the ventricle are best left behind unless they are readily accessible. They can be removed secondarily if necessary. Ventricular injuries frequently give rise to unexplained cyclical fevers and endocrine abnormalities. When patients are operated on within 12 hours of the injury, many tracks and most bone chips are sterile. When treatment is delayed, secondary contamination occurs. Any single individual bone fragment is probably sterile, but each track is likely to include fragments of contaminated bone. Metal fragments, on the other hand, rarely become foci of infection.
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A number of anatomic and neurologic observations have been found to carry important prognostic implications. In pre-CT series, disruption of more than one third of the ventricular wall was invariably fatal. The syndrome of coma, fixed dilated pupils, Cheyne-Stokes respirations, and spastic quadraparesis or flaccidity was thought by Matson to be incompatible with recovery in a wartime setting. Raimondi and Samuelson assigned patients to one of five categories according to neurologic status on admission (Table 3).19 Patients who were alert and who had never lost consciousness (group I) or who had a focal deficit only (group II) invariably survived. Somnolence, agitation, or confusion following loss of consciousness (group III) was associated with a 35% mortality. Obtundation with response to voice or pain, or coma without abnormal motor posturing (group IV) had an associated mortality of 75%. Coma with posturing (group V) was not survived. Bymes et al.6 related outcome to consciousness and vital signs on admission. No patient in deep coma survived. Only 4% of those with fixed and dilated pupils survived. Less than 25% of patients responsive to deep pain only survived. Those who were alert, slightly drowsy, reactive pupils almost always survived. Similar data were amassed by Carey et al. in Vietnam.*” CrockardZ5 examined head-injured patients in Belfast within 20 minutes of wounding. ICP proved ineffective as a prognostic measure. Arterial hypertension, in contrast, proved highly significant: Hypertension above 160 systolic carried a 93% morbidity. One important question arises in all pre-CT scan studies: could the prognosis have been improved by the evacuation of accessible hematomas that were missed, or was the examination on presentation prognostically valid regardless of other considerations? In the only major study using CT to eliminate the possibility of major space-occupying lesions, Hubschmann et aLZ6 demonstrated that the level of alertness and other neurologic signs accurately correlated with functional outcome (Table 4).
OUTCOME Over the past 30 years, one thing has become increasingly clear: although the survival after penetrating missile injuries can be improved by the measures just discussed, functional recovery is in many cases worse than what might have been traditionally predicted. So sensitive is the brain to high energy forces from penetrating missiles that careful neuropsychological evaluation of the type carried out by the VHIS has successfully demonstrated subtle but consistent deficits even in the absence of major tissue loss. No study has documented the long-term outcome of missile injuries in a civilian population.
DAGI n MISSILE INJURIES TO THE BRAIN
TABLE4. Functional Outcome*
Grade I II Ill IV
Total
Outcome
Findings on Admission
Total
Patients Undergoing Operation
Alert, awake Obtunded, with or without focal deficit Responsive to noxious stimuli only Comatose, posturing 39 or no response to noxious stimuli after resuscitation
14 21
13 19
14 16
0 2
0 3
8
7
2
2
4
39
6
0
0
39
82
45
32
4
48
Functional
Nonlunctional
Died
Key: Functional: intact, or with focal deficit, but independent; Nonfunctional: severe deficit preventing independent function or requiring institutional care. lHubschmann 0, Shapiro K, Baden M, et al. Craniocerebral gunshot injuries in civilian practice-prognostic criteria and surgical management: Experience with 82 cases. J Trauma 1979; 196-12.
The well-known long-term sequelae of penetrating injuries include recurring and delayed infection, sometimes as long as 25 or 30 years after injury, and seizure disorders. There is nothing that can be done in the emergency setting, preoperatively, to affect the incidence of these problems. Surgical technique can have a limited, albeit a definite influence on long-term outcome. It is important to remember, however, that when a patient with a history of penetrating missile injury presents with an acute neurological event, a correlation between the two must be rule out. CONCLUSION Penetrating injuries of the head need not be invariably fatal. Through careful resuscitation, thorough search for operable lesions, and meticulous surgical technique, almost every patient who is not in a coma should survive. A satisfying functional recovery can be achieved by attention to the details of resuscitation and initial assessment.
REFERENCES 1. Cushing H. A study of a series of wounds involving the brain and its enveloping structures. Br J Surg 1918;8:558-684 2. Meirowsky AM (ed). Neurological Surgery of Trauma. Washington, DC, Office of the Surgeon General, 1964 3. Matson DD. The Treatment of Acute Craniocerebral Injuries due to Missiles. Springfield, Illinois, Charles C. Thomas, 1948 4. British Journal of Surgery. War Surgical Supplement, 1947 5. Lewin W, Gibon MR. Missile head wounds in the Korean campaign: A survey of British casualkies. Br J Surg 1956;43:628-632 6. Byrnes DP, Crockard HA, Gordon DS, et al. Penetrating craniocerebral missile injuries in the civil disturbances in Northern Ireland. Br J Surg 1971;61:169-176
7. Meyers PW, Salazar AM. Vietnam Head Injury Study: Combatcaused penetraitng head wounds-assessment 14 years after injury. Presented in part April 27, 1986, Course 104, Annual Meeting, American Academy of Neurology. (Manuscript in preparation) 8. Markush RE, Bartolucci AA. Firearms and suicide in the United States. Am J Public Health 1984;74:123-127 9. Demuth WE Jr. Bullet velocity as applied to military rifle wounding capacity. J Trauma 1969;9:27-32 10. Demuth WE Jr. Bullet velocity and deisng as determinants of wounding capability. An experimental study. J Trauma 1986;6:222-232 11. Dobbyn RC, Bruckly WL Jr, Shubin LD. An Evaluation of Police Handgun Ammunition: Summary Report. Washington DC US Department of Justice, 1975 12. Dodge PR, Meirowsky AM. Tangential wounds of the scalp and skull. J Neurosurg 1952;9:472-483 13. Adelola A, Odehus EL, A syndrome characteristic of tangential bullet wounds of the vertex of the skull. J Neurosurg 1971;34:155-158 14. Harvey EW, Butler EG, McMillen JH, et al. Mechanisms of wounding. War Med 1945;8:91-104 15. Kirpatrick JB, DiMaio VD. Civilian gunshot wounds of the brain. J Neurosurg 1978;49:185-198 16. Meirowsky AM. Secondary removal of retained bone fragments in missile wounds of the brain. J Neurosurg 1982;57:617-621 17. Harmon WM. Retained intracranial bone fragments: Analysis of 42 patients. J Neurosurg 1971;34:142-154 18. Freytag E. Autopsy findings in head injuries from firearms: Statistical evaluation of 254 cases. Arch Pathol 1983;76:215-225 19. Raimondi AS, Samuelson GH: Craniocerebral gunshot wounds in civilian practice. J Neurosurg 1970;32:647-853 20. Crockard HA. Bullet injuries of the brain. Ann Coll Surg Engl 1974;55:111-123 21. Barnett JC, Meirowsky AM. Intracranial hematoma associated with penetrating wounds of the brain. J Neurosurg 1955;12:34-48 22. Matson DD, Wolkin J. Hematoma associated with penetrating wounds of the brain. J Neurosurg 1946;3:46-53
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23. George ED, Dagi TF. Penetrating missile injuries of the head. ln Schmidek H, Sweet WH (eds). Operative Neurosurgery, ed 2. New York, Grune and Stratton. In press 24. Carey ME, Young H, Mathis JL. The neurosurgical treatment of craniocerebral missile wounds in Vietnam. Surg Gynecol Obstet 1972;135:386-390
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25. Crockard HA. Early intracranial pressure studies in gunshot wounds of the brain. J Trauma 1975;15:339-347 26. Hubschmann 0, Shapiro K, Baden M, et al. Craniocerebral gunshot injuries in civilian practice-prognostic criteria and surgical management: Experience with 82 cases. J Trauma 1979;19:6-12