Based on the speed of penetration, it can be classified into two categories:
Traumatic brain injury (TBI) is one of the leading causes of death in the United States. Although penetrating trauma is less common than closed head trauma, it carries a worse prognosis. Most deaths from traumatic brain injury are due to firearm injuries. In the United States, approximately 20,000 gunshot injuries to the head occur annually.[6][7]
The consequences of penetrating head injury depend on the following factors:
Primary injuries occur immediately. Secondary injuries occur following the time of the injury. The final neurologic outcome is influenced by the extent and degree of secondary brain injury. Therefore, the primary goal in the emergency department is to prevent or reduce conditions that can worsen outcomes, such as hypotension, hypoxia, anemia, and hyperpyrexia.
The amount of damage to the brain depends on the kinetic energy imparted to the brain tissue. This, in turn, depends on the following factors:
The presentation depends on the mechanism, site of the lesions, and associated injuries.
History should include:
Initial physical examination includes primary and secondary trauma survey with the evaluation of other distracting injuries. A complete physical examination should be performed including a neurological examination. This should include documentation of the Glasgow coma scale (GCS). The involvement of cranial nerves should be assessed, and motor/sensory examination should be performed. It is important to realize that neurologic injury may be manifest distant to the site of impact. If unable to fully and formally assess cranial nerves secondary to lack of patient cooperation, it is important to, at least, document any findings relevant to the patient’s neurology.
In the pre-hospital setting, or in non-trauma facilities, stabilize, but, do not remove penetrating objects such as knives. Patients should be transported quickly to a location capable of providing definitive care. Early recognition of high-risk mechanisms, early imaging, and early evaluation at a level 1 trauma center may improve outcomes.[8][9]
In the emergency department, resuscitation and stabilization should be provided. Manage ABCDE’s using Advanced Trauma Life Support (ATLS) guidelines. Perform a primary survey to identify any life-threatening injury. Stabilize, focusing on the airway, breathing, and circulation, including external hemorrhage, while establishing and maintaining cervical spine immobilization. Early activation of a trauma team may help to provide prompt recognition of polytrauma. The target is to maintain a systolic blood pressure of at least 90 mm Hg.
Following initial resuscitation and stabilization, an inspection of the superficial wound should be performed. Identify the entrance wound (and exit wounds, if present). Beware that blood-matted hair may cover these wounds. When a patient presents with a gunshot wound to the head, the other parts of the body including neck, chest, and abdomen should be inspected carefully for other gunshot wounds. Beware that injuries to the heart or great vessels in the chest or abdomen may be even more life-threatening.
A subgaleal hematoma can become extensive because blood easily dissects through the loose areolar tissue; such a hematoma can be a cause of hemodynamic compromise. Apply a sterile dressing to both the entrance and exit wounds. Assess whether there is any oozing of cerebrospinal fluid (CSF), blood, or brain parenchyma from the wound. Evaluate for hemotympanum, which may indicate a basilar skull fracture. Examine all orifices for retention of foreign bodies, the missile, teeth, and bone fragments.
Perform neurological examination, including GCS and document well. Evaluating for signs suggesting raised intracranial pressure is critical. The initial signs and symptoms may be nonspecific and include a headache, nausea, vomiting, and papilledema.
Perform a careful examination of the neck, chest, abdomen, pelvis, and extremities. Assume multiple injuries in cases of penetrating trauma. Obtain a detailed history including the “AMPLE” history with an emphasis on events surrounding the injury. Also, determine the weapon type and/or caliber of the weapon.
CT Scan
If the patient is hemodynamically stable, obtain a Computed Tomography (CT) scan of the head to evaluate for the presence of a mass lesion (hematoma) or cerebral edema. It can be obtained when the patient is stabilized and ready to be transported to the radiology department. A CT scan can adequately identify the extent of the intracranial injury and can also determine the relationship between the penetrating object and the intracranial structures. However, a radiolucent object, such as a wooden object, maybe missed by the CT scan. In patients with penetrating head trauma, a large mass or hematoma may be evident. If ICP is increased, aqueductal stenosis is present, and the third but not fourth ventricle is enlarged.
Certain factors are important in critical decision making and have prognostic implications. These may include the following:
Plain Radiograph
Maybe useful as it provides information about the following:
Computed Tomographic Angiography (CTA)
If a vascular injury is suspected, noninvasive investigative CTA should be obtained after patient stabilization.
Magnetic Resonance Imaging (MRI) Scan
Additionally, an MRI Scan may be obtained if penetrating objects are suspected to be wooden objects. It should not be performed if intracranial metallic fragments are present. Such a procedure is contraindicated. However, if no bullets or intracranial metallic fragments are present, then an MRI scan of the brain can be performed in a stable patient. This can provide information about the posterior fossa structures and the extent of possible shared injuries.
Patients with penetrating head trauma require both medical and surgical management.[10][11][12]
Medical Management
A low threshold for obtaining surgical consultation should be considered in cases of penetrating head trauma. Beware that many patients with penetrating head trauma will likely require operative intervention.
Indeed, do not remove any penetrating object from the skull in the emergency department until trauma and neurosurgical evaluation is obtained. Also, the protruding object should be stabilized, and provision should be made to protect it from moving during transportation of the patient, to prevent further injury.
Assess the need for endotracheal intubation.
Normalize PCO2. Avoid hyperventilation, because it leads to vasoconstriction and a subsequent reduction in the cerebral perfusion pressure (CPP). This may worsen long-term neurological outcome. Beware that hyperventilation is only a temporizing measure for the reduction of elevated intracranial pressure (ICP). Avoid hyperventilation during the first 24 hours after injury when cerebral blood flow (CBF) often is reduced.
Monitor intracranial pressure (ICP) particularly in patients with GCS less than 8. Consider head elevation to 30 degrees. This can improve venous drainage and may decrease ICP. The target is to maintain intracranial pressure (ICP) less than 20 mmHg to 25 mmHg and CPP greater than 70 mmHg. Since cerebral blood flow (CBF) is difficult to measure continuously, the CPP is measured as a surrogate. Treatment typically is indicated for ICP greater than or equal to 20 mmHg to 25 mmHg, with guideline goals of ICP less than 20 mmHg and cerebral perfusion pressure (CPP) 50 mmHg to 70 mmHg.
Surgical Management
A major reason for surgical intervention is the presence of a hematoma. Large hematomas should be evacuated promptly. Early decompression with conservative debridement of the brain may be needed. In most cases, the removal of a deep-seated bullet may not be required. However, there are certain indications when removal should be considered. These are:
A craniotomy is needed for low-velocity missile wounds in which the object is still protruding from the head. Some critical factors can determine the outcome for those who survive the initial injury; they depend on prompt and early surgical intervention as well as the ability to provide high-level neurocritical care.
Avoid the use of a nasogastric tube if there may be a skull-base fracture. i.e., there is a risk of intracranial tube insertions or risk of significant bleeding during surgical removal of the penetrating object.
Beware that traumatic aneurysms are more susceptible to rupture than are congenital aneurysms.
Avoid using the entry or exit wounds when planning scalp incisions.
Penetrating head trauma is best managed by an interprofessional team that consists of a neurosurgeon, emergency department physician, neurologist, intensivist, neurosurgical nurses, physical therapy and an internist. When the brain is injured, this can lead to impairment in almost every organ system. The key is to prevent further complications like pressure sores, deep vein thrombosis, failure to thrive, aspiration pneumonia and contractures. Healthcare workers should be proactive and involve speech, occupational and physical therapists early on in treatment. The overall outlook for patients with penetrating head trauma depends on age, comorbidity, extent, and site of brain injury and presence of neurological deficits at the time of presentation. Even those who survive, the recovery can take months or years. Residual neurological deficits are common in survivors.[16] (Level V)
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