|
Managing Closed Head Injury
The authors review the anatomy of the head, discuss how to assess and manage closed head injuries in different patient populations, and offer imaging guidelines.
By Heather H. Costello, MD, MA, and Peter S. Pang, MD
More than two million people visit U.S. emergency departments each year because of head trauma. Approximately 50,000 people die from head injuries every year, making it the leading cause of traumatic death in people under age 25.
Head injury occurs in infants, children, adolescents, adults, and the elderly. Vulnerability to head injury also transcends sex, socioeconomic status, and ethnicity. Causes are varied as well, ranging from blunt to penetrating trauma resulting from abuse, sports injuries, falls, and battery, to name just a few. Patient presentations may be complicated by an inability to communicate, anticoagulation therapy, alcohol abuse, and physiologic and anatomic changes secondary to aging or alcoholism.
Equally diverse are the ways in which emergency physicians evaluate and manage the head injured patient. In the United States, computed tomography (CT) scanning has become a unifying factor; the major decision point in head trauma evaluation is whether diagnostic imaging is warranted. Certain clinical presentations seem to be universal indicators for CT imaging—for example, patients under six months old; elderly patients; patients with prolonged loss of consciousness (LOC), persistent vomiting, or neurologic deficits; and those on anticoagulant therapy. However, most patients do not fit into these clearly defined high-risk groups.
Ideally, assessment guidelines should be sensitive enough to capture all significant head injuries and specific enough to avoid unnecessary imaging. Besides the clinical concerns, there are medicolegal ramifications to missing a devastating head injury. This leads to a certain amount of “defensive” medicine. Searching the Internet for closed head injury (CHI) produces as many Web sites about medical evaluation and management as it does lawyers seeking patients with supposedly poorly managed CHIs.
This article will review the anatomy of the head and discuss evaluation options, issues surrounding special patient populations, and guidelines for management of the patient with CHI, also called traumatic brain injury.
ANATOMY OF THE HEAD
The anatomy of the head provides a natural resilience to injury. The scalp consists of five layers: the thick dermis, the subcutaneous tissue with its large and small blood vessels, the dense galea with the temporoparietalis and occipitofrontalis muscles, the areolar tissue layer, and the adherent pericranium. The next barrier to injury is the interwoven frontal, ethmoid, sphenoid, occipital, parietal, and temporal bones of the cranium, which connect circumferentially to provide resistance to fracture. An adult’s skull ranges in thickness from 2 to 6 mm, with the thickest part in the occipital bone and the thinnest in the temporal bone.
The average three-pound brain, covered in the pia, arachnoid, and dura mater layers, floats in the surrounding cerebrospinal fluid (CSF) and fills approximately 80% of the cranium. But despite an anatomically protective design, the brain still gets injured. For example, the rough bony surface inferior to the brain can be a potential source of injury if the brain comes into contact with it during acceleration/deceleration.
About 6% of CHI patients have significant intracranial injuries. Although only 1% require neurosurgical intervention, the outcomes of these injuries can be devastating.
PATHOPHYSIOLOGY OF CLOSED HEAD INJURY
After injury, several types of damage to the skull and brain tissue may occur. Gross structural damage includes skull fractures, contusions, hemorrhages, and hematomas. Recent studies have examined the role of neuronal loss and axonal injuries as structural sequelae of CHI. Axonal injury in particular has been primarily found in the fornices, which are important regions of the brain for cognition and memory. This finding correlates well with patients’ complaints of memory loss, confusion, and concentration difficulties. Structural damage from head trauma causes the breakdown of membrane lipids and the release of free radicals and catecholamines. The membrane lipids fragment into inflammatory mediators such as prostaglandins. Patients with moderate to severe head injury and high serum levels of prostaglandins have recently been shown to have worse outcomes than those with lower levels of prostaglandins. Possible secondary insults to brain-injured patients are hypotension and hypoxia, which are critical to avoid during resuscitation. Prevention of secondary injury is a cornerstone of management. Thus, emergency department management should also include supplemental oxygen or airway control with intubation, as necessary, along with hemodynamic support to ensure adequate cerebral perfusion.
TYPES OF CLOSED HEAD INJURIES
Head injury has a wide range of etiologies, including direct force by a blunt or penetrating object and acceleration/deceleration forces that cause the brain to move forcibly against the inside of the cranium. The spectrum of skull fractures ranges from linear, nondepressed fractures where the scalp remains intact to potentially life-threatening open, depressed fractures with associated intracranial hemorrhage and ensuing infection. Although the petrous portion of the temporal bone is the most common site for a basilar skull fracture, this type of fracture may occur at any point in the base of the skull. The emergency physician should be aware of the classic signs of a basilar skull fracture, which include retroauricular ecchymosis (Battle’s sign), periorbital ecchymosis (raccoon eyes), otorrhea or rhinorrhea containing CSF, and hemotympanum.
Penetrating injuries can occur from high-velocity objects of any shape or from sharp objects with low- to high-velocity trajectories. Size, force, and location determine the seriousness of the injury. With rare exceptions, all patients with penetrating head trauma should be stabilized, undergo CT imaging (unless immediate operative intervention is required or other trauma-related issues take precedence), and have a neurosurgical consultation.
Most head trauma results from acceleration/deceleration injuries, which can range from concussion or contusion to traumatic bleeding.
We will now discuss six common CHIs: concussion, brain contusion, traumatic subarachnoid hemorrhage, traumatic subdural hematoma, traumatic epidural hematoma, and diffuse axonal injury (DAI).
Concussion. A concussion is a diffuse injury unlikely to be seen on CT scan and is therefore a clinical diagnosis. Patients may have transient LOC after blunt trauma to the head. Amnesia and confusion may be present without focal neurologic deficits. In most cases, patients recover completely, but detailed discharge instructions listing specific age-related warning signs of increased intracranial pressure (ICP) are a necessity. Additionally, it is important to discuss potential long-term complications of concussion, such as headache, dizziness, anxiety, or memory problems, which may take weeks or longer to resolve. Not only is this excellent patient care, but it may also reduce the number of return visits to the emergency department.
Brain contusion. A brain contusion is a serious injury that occurs either directly under the area of impact or on the contralateral side of the head (a coup or contrecoup lesion). Unlike a concussion, a contusion results from focal trauma to the parenchymal blood vessels, leading to petechial hemorrhages and surrounding edema. This may result in an expanding mass effect. The initial insult is to the gray matter, which gradually infiltrates the white matter. The most common locations for contusion are the subfrontal cortex and frontal lobe. Patients usually present later with focal neurologic deficits, prolonged confusion, or even coma. They require close observation and continuous neurologic assessment because this focal injury can progress to herniation, depending on its location.
Traumatic subarachnoid hemorrhage. Traumatic subarachnoid hemorrhage results from shear force tearing the small subarachnoid vessels. Patients classically present with diffuse headache and photophobia. A noncontrast CT scan may demonstrate increased density within the basilar cisterns or the inter-hemispheric fissures and sulci. Scans done immediately or within a few hours of the injury may be falsely negative, so if clinical suspicion is high, follow-up CT scans are indicated. Patients with traumatic subarachnoid hemorrhage have an increased incidence of skull fractures and contusions, so physicians should assess for these injuries too.
Traumatic subdural hematoma. Subdural hematomas may result from various forms of blunt and penetrating trauma. These blood clots form between the dura and the brain after disruption of the superficial bridging vessels. Generally speaking, the more intracranial space the brain has to move in, the greater the probability of subdural hematomas after trauma. Thus, elderly patients and chronic alcoholics are more at risk for subdural hematomas secondary to brain atrophy.
Patients usually present days after the initial injury complaining of headache, declining mental status, and possibly lateralizing signs such as right-sided weakness. Because the bridging vessels are small and venous, development of clinical signs and symptoms is delayed. Eventually, the hematoma can become a significant mass lesion with resultant tissue ischemia from compression. Patients require prompt neurosurgical evaluation and may require evacuation. During the acute or initial phase, CT scan reveals a crescent-shaped hyperdense lesion between the calvaria and cortex that may cross suture lines.
Traumatic epidural hematoma. Epidural hematomas occur between the inner table of the skull and the dura. These clots are usually caused by disruption of the middle meningeal artery or dural sinus. Direct injury to the temporoparietal area resulting in skull fracture is common. Unlike subdural hematomas, epidural hematomas are generally arterial bleeds that develop quickly and are usually detectable by CT scan on initial presentation.
Occasionally, a dural sinus epidural hematoma develops more slowly. Both resultant bleeds appear as lenticular, biconvex, hyperdense lesions usually found in the temporal region. A venous sinus injury, in contrast to an arterial injury, is more often found after a blow to the occiput. Patients typically present with a history of direct head trauma, severe headache, nausea, vomiting, and progressively declining mental status. Development of symptoms correlates with the speed of expansion of the hematoma. Emergency department CT scans may show a variation in density illustrative of active bleeding. Prompt neurosurgical evacuation is mandatory.
Diffuse axonal injury. Once thought to be a primary injury, DAI is now known to have equally devastating secondary injury effects that are only seen at the microscopic level. In addition to acceleration/deceleration injury, rotational forces play a role in DAI. Often, these injuries are not seen on the initial CT scan. While magnetic resonance imaging (MRI) may yield useful information, management of these patients in the emergency department typically does not warrant MRI emergently. The critical areas of damage occur at the interface between the white and gray matter where axons are subjected to shear force, eventually leading to edema and axoplasmic leakage.
Diffuse axonal injury is currently a clinical diagnosis based on the length of coma. Mild DAI patients remain in a coma for 6 to 24 hours, with a mortality rate of 15%. Moderate DAI patients remain in a coma for more than 24 hours and have a mortality rate of 25%. Severe DAI patients remain comatose or in a persistent vegetative state and most have a dismal prognosis or die secondary to their severe head injury.
CATEGORIES OF CLOSED HEAD INJURY
Closed head injuries can be subdivided into mild, moderate, and severe. This division is initially based on the patient’s Glasgow Coma Scale (GCS) score (see box below).
Severe CHI. In emergency medicine, there is no single unifying definition or delineation of the severity of CHI. Various authors and professional organizations have formulated different rules and inclusion criteria. In this article, CHI will be subcategorized using definitions from Rosen’s Emergency Medicine: Concepts and Clinical Practice.
According to Rosen’s, severe CHI is defined as a GCS score of 8 or less on presentation and includes patients with lacerations, hematomas, and intracranial contusions. Severe CHI accounts for 10% of all head injury patients, with a 60% overall mortality, although mortality is lower in children. Severe head injury patients require airway management, preferably using pretreatment with lidocaine (1.5 to 2 mg/kg IV) to reduce the increased intracranial pressure (ICP) effects of intubation, if time allows. They may also need a premedication dose of a nondepolarizing agent if succinylcholine will be used.
If signs of increased ICP evolve, such as unequal pupils or worsening of the GCS score, consider using mannitol (0.25 to 1 gm/kg IV) to reduce ICP if hypotension is not present. Mannitol creates an osmotic gradient, moving water into the vascular space, reducing brain volume to compensate for brain swelling or expanding hematomas. Despite traditional practice, prophylactic hyperventilation is no longer recommended. Ventilator settings should be based on oxygenation needs, and appropriate tidal volumes should be based on the patient’s ideal weight. For patients with subarachnoid hemorrhage, nimodipine has been shown to reduce mortality by preventing vasospasm.
After stabilization, all severe head injury patients should undergo imaging to further evaluate the extent of intracranial injury. Of course, other traumatic injuries may influence management, so assessment should fall within the scope and prioritization of overall trauma management. These patients will probably require neurosurgical consultation and admission to an appropriate intensive care unit. Ultimately, MRI is usually necessary for further delineation of soft tissue injury.
Moderate CHI. Moderate head trauma is defined in Rosen’s as a patient presenting with a post-resuscitation GCS score of 9 to 13. These patients require close attention and observation because the range of presenting signs and symptoms is diverse and deterioration is common. Prognosis for patients with moderate CHI who subsequently deteriorate to severe injury is worse than for those whose initial evaluation is severe CHI. As a general rule, once these patients are stabilized, they require an initial CT scan and admission for observation and continued neurological examination.
Minor CHI. Evaluating, diagnosing, and treating minor head trauma is more difficult than moderate or severe injury. Most head injury patients presenting to the emergency department have minor trauma. Definitions of minor CHI are variable, but Rosen’s defines it as an isolated injury with a GCS score of 14 or 15. This definition is subcategorized into patients at high, medium, or low risk, which helps physicians decide whether to order a CT scan and if a patient requires admission or just observation (see box below).
 |
Initial evaluation of the minor CHI patient should include the following: assessment of mental status; determination of GCS score; thorough neurologic evaluation; careful physical examination to assess for lacerations, abrasions, hematomas, or palpable fractures; ear examination to look for hemotympanum or otorrhea; examination of the cervical spine for bony point tenderness or step-offs; consideration of a hard collar; examination of pupils for reactivity and anisocoria; and assessment of cranial nerve and brain stem functions. Asking the patient about the use of anticoagulants, other blood thinning medications, and alcohol consumption is also important. Careful documentation is crucial for both patient care and medicolegal reasons. Documentation should reflect any history of head injuries, preexisting pain issues secondary to previous head injuries, residual deficits or disabilities, and psychiatric issues, and, when possible, should allow comparison with previous imaging studies.
Because head injury is often only one aspect of a trauma evaluation, the initial evaluation and screening should be considered in light of a global trauma assessment. As mentioned earlier, blood pressure support and supplemental oxygen are important emergency department interventions, not only as part of overall high-quality trauma care, but also to prevent secondary injury. Some patients with minor head injury require only reassurance and careful discharge instructions. However, the following laboratory tests should be considered: complete blood count, chem-7, coagulation studies, and blood alcohol and toxicologic screening. Complete blood count and chemistry, toxicology, and blood alcohol level establish baseline parameters and may also reveal potential toxic metabolic causes of injury. Coagulation studies are especially important for patients taking coumadin.
SPECIAL PATIENT POPULATIONS
When evaluating traumatic brain injury in elderly patients, those taking anticoagulants, and alcoholic patients, consider the following special concerns.
Elderly patients. Evaluating the elderly patient with a head injury can be challenging. Age-related volume loss makes the elderly patient’s brain more susceptible to acceleration/deceleration injuries. Because the relative distance between brain tissue and the bony inner calvarium is increased, this creates more distance to accumulate velocity and force, increasing the potential for injury. The bridging veins also span a greater distance, so they tear more easily and lose integrity. These structural changes make the patient more susceptible to CHI, even in the minor category, so imaging should be strongly considered in the majority of cases.
Despite the unique characteristics of the elderly population, examination of these patients after head injury should follow the same guidelines as for the uncomplicated adult patient. Because many injuries go unwitnessed, pay special attention to the mechanism of injury and always consider abuse, especially if the reported mechanism of injury and presentation do not correlate. Keep in mind that the patient history may be insufficient or unreliable, the physical examination may also be unreliable, and symptoms secondary to dementia may occasionally cloud the picture. Therefore, the emergency physician should err on the side of caution and use CT imaging if there is any suspicion of a potentially significant head injury.
Patients on anticoagulant therapy. Many CHI patients are on anticoagulation therapy for comorbid conditions, such as deep vein thrombosis or atrial fibrillation. No matter their age, these patients warrant a thorough evaluation, even in the setting of a presumed minor CHI. Blood work should include prothrombin time/international normalized ratio/partial thromboplastin time (PT/INR/PTT) to assess for potential supratherapeutic anticoagulation. Patients on warfarin with a supratherapeutic INR may require fresh frozen plasma to reverse the anticoagulation effects. Although young patients on anticoagulation therapy have less risk of CHI from minor trauma than elderly patients, a missed diagnosis can be devastating. So strongly consider imaging for patients of all ages, even if they have only minor head injuries.
Alcoholism. Chronic alcoholism causes brain atrophy and other structural brain damage, as well as coagulopathic changes secondary to liver damage. This combination creates a high potential for serious injury in the setting of even minor CHI. Often, the alcoholic patient may be unable to describe an injury or even know there was one. These patients may present to the emergency department immediately after injury or days later, or they may be unconscious and found by emergency medical services. A thorough history is invaluable, with input from the patient’s family or friends, if possible. In light of an often absent or unreliable history, these patients warrant CT evaluation if any suspicion of CHI exists.
RULES FOR CT IMAGING
Widespread and easy access to CT scanning has increased the use of this diagnostic test. However, scans are costly in terms of money, time, radiation exposure, and general resource utilization in the emergency department. Guidelines have been established to help physicians decide when scans are necessary to detect potentially serious injury and when they are unnecessary. Here we will review the Canadian CT Head Rule, the New Orleans Criteria, and the Eastern Association for the Surgery of Trauma (EAST) Practice Management Guidelines. Each set of rules begins with a definition of minor head injury.
Canadian CT Head Rule. The Canadian CT Head Rule defines minor head injury as a GCS score of 13 to 15, with a history of LOC, amnesia, or disorientation. These guidelines were created after an observational study revealed significant variation among similar Canadian teaching hospitals in their use of CT scanning for minor head injury assessment.
The Canadian study excludes patients with the following characteristics: younger than age 16, obvious penetrating trauma or depressed skull fracture, acute focal neurologic deficits, unstable vital signs associated with major trauma, seizure before presentation in the emergency department, anticoagulation therapy or bleeding disorders, and those with LOC, amnesia, or disorientation. The outcomes measured for this study were the need for neurologic intervention or clinically important brain injury per CT results, or both.
Data analysis broke the cohort into three risk groups. Those deemed at high risk for neurosurgical intervention after CT scan met one of the following criteria: a GCS score of less than 15 at two hours after injury, suspected open or depressed skull fracture, any sign of basal skull fracture, vomiting two or more times, and age 65 or older. Patients considered at medium risk for brain injury after CT scan were those whose amnesia lasted for more than 30 minutes after impact or those with a dangerous mechanism of injury—for example, a pedestrian struck by a motor vehicle, a person ejected from a motor vehicle, or a person who fell from height of more than three feet or five stairs. The low-risk group included those with witnessed LOC, definite amnesia, or disorientation with a GCS score of 13 to 15.
Of the 3000 patients studied, 1% required neurosurgical intervention, including four who died of their head injuries, and 8% had clinically important brain injuries requiring hospital admission and neurologic follow-up. The Canadian CT Head Rule was found to be 100% sensitive for the high-risk subgroup and 98% sensitive for all seven factors of high-risk and medium-risk patients. In summary, this rule states that all patients with moderate or severe CHI should undergo CT scanning and patients with minor head trauma should have scans if any high-risk or medium-risk signs or symptoms are present.
New Orleans Criteria. The New Orleans Criteria define minor head trauma as LOC in patients with a normal neurologic examination as determined by the emergency physician. Loss of consciousness was considered present if the patient or a witness corroborated this history or if the patient could not remember the traumatic event. Besides LOC, any one of the following criteria also warrants a CT scan: headache, vomiting, age over 60, drug or alcohol intoxication, short-term memory loss, seizure, or evidence of injury above the clavicles. This study had a 100% sensitivity in detecting significant head injury in patients with any of these indicators. Of the 1733 patients studied, 0.5% needed neurosurgical intervention and 5% had significant brain injuries.
The EAST Practice Management Guidelines. In 2001, EAST published guidelines for the management of mild traumatic brain injury. The association’s definition of mild CHI is an injury caused by blunt acceleration/deceleration forces that produces unconsciousness for 20 minutes or less or brief retrograde amnesia, a GCS score of 13 to 15, no focal neurologic deficit, no intracranial complications (such as seizure activity), and normal CT findings. This definition, which includes CT findings, requires a scan in order to exclude moderate or severe head injury based on radiologic findings.
These guidelines focus more on the definitive management of CHI patients after diagnostic testing has been performed, rather than on an algorithm to determine who requires testing. According to EAST, the literature supports the use of CT scanning for all cases of minor CHI in which one or more of the following is found: LOC, post-traumatic amnesia, confusion, or impaired alertness.
Closed head injury is a common but potentially serious problem encountered frequently by ED physicians. Knowing what evaluation tools to use and when imaging is necessary will ensure that patients receive the best care possible.
Suggested Reading
Cushman JG, et al.: Practice Management Guidelines for the Management of Mild Traumatic Brain Injury. The Eastern Association for the Surgery of Trauma Web site. Available at http://www.east.org/tpg/tbi.pdf. Accessed on May 4, 2007.
Garra G, et al.: Minor Head Trauma in Anticoagulated Patients. Acad Emer Med 6(2):121, 1999.
Haydel MJ, et al.: Indications for computed tomography in patients with minor head injury. N Engl J Med 343(2):100, 2000.
Heegaard WG and Biros MH: Head. In Marx JA, et al. (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, 6th ed, Mosby, 2006, p. 349.
Lavoie A, et al.: Preinjury warfarin use among elderly patients with closed head injuries in a trauma center. J Trauma 56(4): 802, 2004.
Ma OJ: Head Injury. In Ma OJ, et al. (eds): Emergency Medicine Manual, 6th ed, McGraw-Hill, 2004, p. 774.
Olson DA: Head Injury. eMedicine Web site. Available from http://www.emedicine.com/NEURO/topic153.htm. Accessed on May 4, 2007.
Stiell I, et al.: The Canadian CT Head Rule for patients with minor head injury. Lancet 357(9266):1391, 2001. |
|
