Meaning Of The Word Penetrate

[Liliane Hubright]

Somecommon synonyms of penetrate are enter, pierce, and probe. While all these words mean "to make way into something," penetrate carries a strong implication of an impelling force or compelling power that achieves entrance.

Penetrating head injuries can be the result of numerous intentional or unintentional events, including missile wounds, stab wounds, and motor vehicle or occupational accidents (nails, screwdrivers). Stab wounds to the cranium are typically caused by a weapon with a small impact area and wielded at low velocity. The most common wound is a knife injury, although bizarre craniocerebral-perforating injuries have been reported that were caused by nails, metal poles, ice picks, keys, pencils, chopsticks, and power drills. [7, 8]

In a study of 14 children with intracranial injuries due to spring- or gas-powered BB or pellet guns, 10 of the children required surgery, and 6 were left with permanent neurologic injuries, including epilepsy, cognitive deficits, hydrocephalus, diplopia, visual field cut, and blindness. According to the study authors, advances in compressed-gas technology have led to a significant increase in the power and muzzle velocity of such guns, with the ability to penetrate a child's skull and brain. [9]

Siccardi et al prospectively studied a series of 314 patients with craniocerebral missile wounds and found that 73% of the victims died at the scene, 12% died within 3 hours of injury, and 7% died later, yielding a total mortality of 92% in this series. [10] In another study, gunshot wounds were responsible for at least 14% of the head injury-related deaths. [1] A study using multiple logistic regressions found that injury from firearms greatly increases the probability of death and that the victim of a gunshot wound to the head is approximately 35 times more likely to die than is a patient with a comparable nonpenetrating brain injury. [11]

The assessment of patients with penetrating brain injuries should include routine laboratory tests, electrolytes, and coagulation profile. Many patients have lost a significant amount of blood before reaching the emergency department or might present with disseminated intravascular coagulation (DIC); consequently, determining the hemoglobin concentration and platelet count is important. Type and cross match should always be obtained with the initial orders. Obtaining a toxicology screen, including alcohol levels, is also appropriate.

The radiologic methods of evaluation depend on the patient's condition. In general, a lateral cervical spine and chest radiographs are obtained in the resuscitation room. A CT scan of the head should be obtained as soon as the patient's cardiopulmonary condition has been stabilized to determine the extent of intracranial damage and the presence of intracranial metallic fragments. The study always should include bone windows to evaluate for fractures, especially when the skull base or orbits are compromised. Some centers can perform CT angiography (CTA) for the evaluation of intracranial and extracranial vessels. Multidetector-row CTA has improved the detectability of both vascular and extravascular injuries in patients with penetrating injuries. [2, 12, 13, 14]

If a vascular injury is suspected and the patient is stable, cerebral angiography often is used to diagnose injuries such as carotid and/or vertebral artery dissections, traumatic pseudoaneurysms, or arteriovenous fistulas.

In patients with penetrating injuries and intracranial metallic fragments, an MRI scan is contraindicated. If the presence of bullets or intracranial metallic fragments has been ruled out, an MRI scan of the brain provides valuable information on posterior fossa structures and the extent of sharing injuries.

Patients with severe penetrating injuries should receive resuscitation according to the Advanced Trauma Life Support guidelines. Specific indications for endotracheal intubation include inability to maintain adequate ventilation, impending airway loss from neck or pharyngeal injury, poor airway protection associated with depressed level of consciousness, and/or the potential for neurologic deterioration. Virtually all individuals with an admission Glasgow Coma Scale (GCS) of 8 or less meet these criteria. [15, 16, 6, 6]

The cervical spine is stabilized, and a careful examination for injuries to the neck, chest, abdomen, pelvis, and extremities is performed. A Foley catheter should be inserted, appropriate IV access secured, and volume replacement started.

The following are significant reasons for surgery: (1) to remove masses such as epidural, subdural, or intracerebral hematomas; (2) to remove necrotic brain and prevent further swelling and ischemia; (3) to control an active hemorrhage; and (4) to remove necrotic tissue, metal, bone fragments, or other foreign bodies to prevent infections.

A National Institutes of Health survey estimates that in the United States, 1.9 million persons annually experience a skull fracture or intracranial injury, and of these cases, 50% have a suboptimal outcome. Firearms account for the largest proportion of deaths from traumatic brain injury in the United States. Each year close to 20,000 persons in the United States are involved in gunshot wounds to the head. [2, 3]

Every year, at least 1.7 million traumatic brain injuries (TBIs) occur in the United States, and they are a contributing factor in 30.5% of all injury-related deaths. Older adolescents (aged 15-19 yr), older adults (aged 65 yr and older), and males across all age groups are most likely to sustain a TBI. The incidence of TBI, as measured by combined emergency department visits, hospitalizations, and deaths, has steadily risen. For example, from 2001 to 2005, the TBI rates increased from 521 to 616 per 100,000 population and, in 2010, increased to 824 per 100,000 population. In addition, deaths related to TBI decreased by 7% over the same 10-year period. [18, 19]

TBI is the leading cause of disability and death in children aged 0-4 yr and adolescents aged15-19 yr. Also, it is estimated that 145,000 children and adolescents (ages 0-19 yr) are living with lasting cognitive, physical, or behavioral effects of TBI. [18, 19]

Approximately 70-90% of patients with penetrating traumatic brain injury (TBI) die before reaching the hospital, and 50% of those who survive to reach the hospital die during resuscitation attempts in the ED. Approximately 35,000 civilian deaths are attributed to penetrating brain injury each year, with firearms-related injuries being the leading cause of mortality in this group. Of the 333,169 US military TBIs recorded between 2000-2015, 4,904 were classified as penetrating TBI. [20]

The pathologic consequences of penetrating head wounds depend on the circumstances of the injury, including the properties of the weapon or missile, the energy of the impact, and the location and characteristics of the intracranial trajectory. [21] Following the primary injury or impact, secondary injuries may develop. Secondary injury mechanisms are defined as pathologic processes that occur after the time of the injury and adversely affect the ability of the brain to recover from the primary insult. A biochemical cascade begins when a mechanical force disrupts the normal cell integrity, producing the release of numerous enzymes, phospholipids, excitatory neurotransmitters (glutamate), and free oxygen radicals that propagate further cell damage.

Missiles range from low-velocity bullets used in handguns, as shown in the image below, or shotguns to high-velocity metal-jacket bullets fired from military weapons. [22, 23] Low-velocity civilian missile wounds occur from air rifle projectiles, nail guns used in construction devices, stun guns used for animal slaughter, and shrapnel produced during explosions. Bullets can cause damage to brain parenchyma through 3 mechanisms: (1) laceration and crushing, (2) cavitation, and (3) shock waves. The injury may range from a depressed fracture of the skull resulting in a focal hemorrhage to devastating diffuse damage to the brain.

As stated previously, a wound in which the projectile breaches the cranium but does not exit is described technically as penetrating, and an injury in which the projectile passes entirely though the head, leaving both entrance and exit wounds, is described as perforating. This distinction has some prognostic implications. In a series of missile-related head injuries during the Iran-Iraq war, a poor postsurgical outcome occurred in 50% of patients treated for perforating wounds, as compared to only 20% of those with penetrating wounds. [24]

In missile wounds, the amount of damage to the brain depends on numerous factors, including (1) the kinetic energy imparted, (2) the trajectory of the missile and bone fragments through the brain, (3) intracranial pressure (ICP) changes at the moment of impact, and (4) secondary mechanisms of injury. The kinetic energy is calculated employing the formula 1/2mv2, where m is the bullet mass and v is the impact velocity.

At the time of impact, injury is related to (1) the direct crush injury produced by the missile, (2) the cavitation produced by the centrifugal effects of the missile on the parenchyma, and (3) the shock waves that cause a stretch injury. As a projectile passes through the head, tissue is destroyed and is either ejected out of the entrance or exit wounds or compressed into the walls of the missile tract. This creates both a permanent cavity that is 3-4 times larger than the missile diameter and a pulsating temporary cavity that expands outward. The temporary cavity can be as much as 30 times larger than the missile diameter and causes injury to structures a considerable distance from the actual missile tract.

Stab wounds (see the image below) represent a smaller fraction of penetrating head injuries. The causes may be from knives, nails, spikes, forks, scissors, and other assorted objects. [7] Penetrations most commonly occur in the thin bones of the skull, especially in the orbital surfaces and the squamous portion of the temporal bone. The mechanisms of neuronal and vascular injury caused by cranial stab wounds may differ from those caused by other types of head trauma. Unlike missile injuries, no concentric zone of coagulative necrosis caused by dissipated energy is present. Unlike motor vehicle accidents, no diffuse shearing injury to the brain occurs.

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