Penetrating head injury
Encyclopedia
A penetrating head injury, or open head injury, is a head injury
in which the dura mater
, the outer layer of the meninges
, is breached. Penetrating injury can be caused by high-velocity
projectiles or objects of lower velocity such as knives, or bone fragments from a skull fracture
that are driven into the brain. A perforating head injury is one in which the object passes through the head and leaves an exit wound. Head injuries caused by penetrating trauma
are serious medical emergencies
and may cause permanent disability
or death
.
In penetrating injury from high-velocity missiles, injuries may occur not only from initial laceration and crushing of brain tissue by the projectile
but also from the subsequent cavitation
. High-velocity objects create rotations and can create a shock wave
that cause stretch injuries, forming a cavity that is three to four times greater in diameter
than the missile itself. A pulsating temporary cavity is also formed by a high-speed missile and can have a diameter thirty times greater than that of the missile. Though this cavity is reduced in size once the force is over, the tissue that was compressed during cavitation remains injured. Destroyed brain tissue may either be ejected from entrance or exit wounds or packed up against the sides of the cavity formed by the missile.
Low-velocity objects usually cause penetrating injuries in the regions of the skull
's temporal bone
s or orbital surfaces, where the bones are thinner and thus more likely to break. Damage from lower-velocity penetrating injuries is restricted to the tract of the stab wound, because the lower-velocity object does not create as much cavitation. However, low-velocity penetrating objects such as slow bullets may ricochet inside the skull, continuing to cause damage until they stop moving.
, penetrating trauma is similar to closed head injury
such as cerebral contusion or intracranial hemorrhage
in a number of ways. As in closed head injury, intracranial pressure
is likely to increase due to swelling
or bleeding, potentially crushing delicate brain tissue. Most deaths from penetrating trauma are caused by damage to blood vessel
s, which can lead to intracranial hematomas and ischemia
, which can in turn lead to a biochemical cascade
called the ischemic cascade
. The injury in penetrating brain trauma is mostly focal (that is, it affects a specific area of tissue).
Studies with PET scanning and transcranial Doppler imaging have shown that changes in cerebral blood flow
, such as hypoperfusion and vasospasm
, can follow penetrating head injury. These changes can last for two weeks. An ischemic cascade
similar to the course of cellular and metabolic events that follow other head injuries may follow penetrating head injuries. Sometimes in penetrating injuries, the brain releases thromboplastin
, which can lead to problems with blood clotting.
While blunt head trauma does not present a risk of shock due to hemorrhage, penetrating head trauma does.
A person with a penetrating head injury may be evaluated using X-ray
, CT scan, or MRI
(however MRI can only be used when the penetrating object would not be magnetic, because MRI uses magnetism and could move the object, causing further injury).
Surgery
may be required to debride
or repair the injury or to relieve excessive intracranial pressure
. Intracranial pressure is monitored and attempts are made to maintain it within normal ranges. Intravenous fluids are given and efforts are taken to maintain high blood oxygen levels.
The highest-velocity injuries tend to have the worst associated damage. Penetrating injury from any missile such as a bullet has a mortality rate of 92%. Thus, firearm
s cause the most head injury-related deaths.
Perforating injuries have an even worse prognosis.
Penetrating head trauma can cause impairment or loss of abilities controlled by parts of the brain that are damaged
. A famous example is Phineas Gage
, whose personality appears to have changed (though not as dramatically as usually described) after a penetrating injury to his frontal lobe
(s).
People with subarachnoid hemorrhage
, a blown pupil
, respiratory distress
, hypotension
, or cerebral vasospasm are more likely to have worse outcomes.
People with penetrating head trauma may have complications such as acute respiratory distress syndrome
, disseminated intravascular coagulation
, and neurogenic pulmonary edema
. Up to 50% of patients with penetrating brain injuries get late-onset post-traumatic epilepsy
.
Fortunate cases exist, e.g., in 2009 a Mississippi woman survived after being shot through the head with a .38-caliber
handgun.
Her condition was such that she was able to offer tea to the arriving police, and she was furthermore expected to make full recovery.
Head injury
Head injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....
in which the dura mater
Dura mater
The dura mater , or dura, is the outermost of the three layers of the meninges surrounding the brain and spinal cord. It is derived from Mesoderm. The other two meningeal layers are the pia mater and the arachnoid mater. The dura surrounds the brain and the spinal cord and is responsible for...
, the outer layer of the meninges
Meninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...
, is breached. Penetrating injury can be caused by high-velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
projectiles or objects of lower velocity such as knives, or bone fragments from a skull fracture
Skull fracture
A skull fracture is a break in one or more of the bones in the skull usually occurring as a result of blunt force trauma. If the force of the impact is excessive the bone may fracture at or near the site of the impact...
that are driven into the brain. A perforating head injury is one in which the object passes through the head and leaves an exit wound. Head injuries caused by penetrating trauma
Penetrating trauma
Penetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out...
are serious medical emergencies
Medical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
and may cause permanent disability
Disability
A disability may be physical, cognitive, mental, sensory, emotional, developmental or some combination of these.Many people would rather be referred to as a person with a disability instead of handicapped...
or death
Death
Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....
.
Mechanisms
Projectile
A projectile is any object projected into space by the exertion of a force. Although a thrown baseball is technically a projectile too, the term more commonly refers to a weapon....
but also from the subsequent cavitation
Cavitation
Cavitation is the formation and then immediate implosion of cavities in a liquidi.e. small liquid-free zones that are the consequence of forces acting upon the liquid...
. High-velocity objects create rotations and can create a shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
that cause stretch injuries, forming a cavity that is three to four times greater in diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
than the missile itself. A pulsating temporary cavity is also formed by a high-speed missile and can have a diameter thirty times greater than that of the missile. Though this cavity is reduced in size once the force is over, the tissue that was compressed during cavitation remains injured. Destroyed brain tissue may either be ejected from entrance or exit wounds or packed up against the sides of the cavity formed by the missile.
Low-velocity objects usually cause penetrating injuries in the regions of the skull
Human skull
The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
's temporal bone
Temporal bone
The temporal bones are situated at the sides and base of the skull, and lateral to the temporal lobes of the cerebrum.The temporal bone supports that part of the face known as the temple.-Parts:The temporal bone consists of four parts:* Squama temporalis...
s or orbital surfaces, where the bones are thinner and thus more likely to break. Damage from lower-velocity penetrating injuries is restricted to the tract of the stab wound, because the lower-velocity object does not create as much cavitation. However, low-velocity penetrating objects such as slow bullets may ricochet inside the skull, continuing to cause damage until they stop moving.
Pathophysiology
Though it is more likely to cause infectionInfection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
, penetrating trauma is similar to closed head injury
Closed head injury
Closed head injuries are a type of Traumatic Brain Injury in which the skull and dura mater remain intact. Closed head injuries are the leading cause of death in children under 4 years old and the most common cause of physical disability and cognitive impairment in young people...
such as cerebral contusion or intracranial hemorrhage
Intracranial hemorrhage
An intracranial hemorrhage is a hemorrhage, or bleeding, within the skull.-Causes:Intracranial bleeding occurs when a blood vessel within the skull is ruptured or leaks. It can result from physical trauma or nontraumatic causes such as a ruptured aneurysm...
in a number of ways. As in closed head injury, intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
is likely to increase due to swelling
Cerebral edema
Cerebral edema or cerebral œdema is an excess accumulation of water in the intracellular or extracellular spaces of the brain.-Vasogenic:Due to a breakdown of tight endothelial junctions which make up the blood-brain barrier...
or bleeding, potentially crushing delicate brain tissue. Most deaths from penetrating trauma are caused by damage to blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s, which can lead to intracranial hematomas and ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...
, which can in turn lead to a biochemical cascade
Biochemical cascade
A biochemical cascade is a series of chemical reactions in which the products of one reaction are consumed in the next reaction. There are several important biochemical cascade reactions in biochemistry, including the enzymatic cascades, such as the coagulation cascade and the complement system,...
called the ischemic cascade
Ischemic cascade
The ischemic cascade is a series of biochemical reactions that are initiated in the brain and other aerobic tissues after seconds to minutes of ischemia . This is typically secondary to stroke, injury, or cardiac arrest due to heart attack. Most ischemic neurons that die do so due to the...
. The injury in penetrating brain trauma is mostly focal (that is, it affects a specific area of tissue).
Studies with PET scanning and transcranial Doppler imaging have shown that changes in cerebral blood flow
Cerebral blood flow
Cerebral blood flow, or CBF, is the blood supply to the brain in a given time. In an adult, CBF is typically 750 millitres per minute or 15% of the cardiac output. This equates to 50 to 54 millilitres of blood per 100 grams of brain tissue per minute. CBF is tightly regulated to meet the brain's...
, such as hypoperfusion and vasospasm
Vasospasm
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...
, can follow penetrating head injury. These changes can last for two weeks. An ischemic cascade
Ischemic cascade
The ischemic cascade is a series of biochemical reactions that are initiated in the brain and other aerobic tissues after seconds to minutes of ischemia . This is typically secondary to stroke, injury, or cardiac arrest due to heart attack. Most ischemic neurons that die do so due to the...
similar to the course of cellular and metabolic events that follow other head injuries may follow penetrating head injuries. Sometimes in penetrating injuries, the brain releases thromboplastin
Thromboplastin
Thromboplastin is a plasma protein aiding blood coagulation through conversion of prothrombin to thrombin.Although sometimes used as a synonym for tissue factor, this is a misconception. Historically, thromboplastin was a lab reagent, usually derived from placental sources, used to assay...
, which can lead to problems with blood clotting.
While blunt head trauma does not present a risk of shock due to hemorrhage, penetrating head trauma does.
Diagnosis and treatment
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
, CT scan, or MRI
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(however MRI can only be used when the penetrating object would not be magnetic, because MRI uses magnetism and could move the object, causing further injury).
Surgery
Surgery
Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...
may be required to debride
Debridement
Debridement is the medical removal of a patient's dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue...
or repair the injury or to relieve excessive intracranial pressure
Intracranial pressure
Intracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
. Intracranial pressure is monitored and attempts are made to maintain it within normal ranges. Intravenous fluids are given and efforts are taken to maintain high blood oxygen levels.
Prognosis
The highest-velocity injuries tend to have the worst associated damage. Penetrating injury from any missile such as a bullet has a mortality rate of 92%. Thus, firearm
Firearm
A firearm is a weapon that launches one, or many, projectile at high velocity through confined burning of a propellant. This subsonic burning process is technically known as deflagration, as opposed to supersonic combustion known as a detonation. In older firearms, the propellant was typically...
s cause the most head injury-related deaths.
Perforating injuries have an even worse prognosis.
Penetrating head trauma can cause impairment or loss of abilities controlled by parts of the brain that are damaged
Brain damage
"Brain damage" or "brain injury" is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors...
. A famous example is Phineas Gage
Phineas Gage
Phineas P. Gage was an American railroad construction foreman now remembered for his improbablesurvival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and...
, whose personality appears to have changed (though not as dramatically as usually described) after a penetrating injury to his frontal lobe
Frontal lobe
The frontal lobe is an area in the brain of humans and other mammals, located at the front of each cerebral hemisphere and positioned anterior to the parietal lobe and superior and anterior to the temporal lobes...
(s).
People with subarachnoid hemorrhage
Subarachnoid hemorrhage
A subarachnoid hemorrhage , or subarachnoid haemorrhage in British English, is bleeding into the subarachnoid space—the area between the arachnoid membrane and the pia mater surrounding the brain...
, a blown pupil
Blown pupil
Blown pupil is an informal medical term used by medical providers to refer to sudden pupillary dilation and loss of ability to constrict in response to light...
, respiratory distress
Respiratory distress
Respiratory distress may refer to either/both:* Labored breathing, the physical presentation of respiratory distress*Shortness of breath or dyspnea - a sensation of respiratory distress-See also:*List of terms of lung size and activity...
, hypotension
Hypotension
In physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
, or cerebral vasospasm are more likely to have worse outcomes.
People with penetrating head trauma may have complications such as acute respiratory distress syndrome
Acute respiratory distress syndrome
Acute respiratory distress syndrome , also known as respiratory distress syndrome or adult respiratory distress syndrome is a serious reaction to various forms of injuries to the lung....
, disseminated intravascular coagulation
Disseminated intravascular coagulation
Disseminated intravascular coagulation , also known as disseminated intravascular coagulopathy or consumptive coagulopathy, is a pathological activation of coagulation mechanisms that happens in response to a variety of diseases. DIC leads to the formation of small blood clots inside the blood...
, and neurogenic pulmonary edema
Pulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
. Up to 50% of patients with penetrating brain injuries get late-onset post-traumatic epilepsy
Post-traumatic epilepsy
Post-traumatic epilepsy is a form of epilepsy that results from brain damage caused by physical trauma to the brain . A person with PTE suffers repeated post-traumatic seizures more than a week after the initial injury...
.
Fortunate cases exist, e.g., in 2009 a Mississippi woman survived after being shot through the head with a .38-caliber
9 mm caliber
This article lists firearm cartridges which have a bullet in the caliber range. The most prevalent of these rounds is the 9x19mm Parabellum.*Length refers to the cartridge case length.*OAL refers to the overall length of the cartridge....
handgun.
Her condition was such that she was able to offer tea to the arriving police, and she was furthermore expected to make full recovery.
See also
- Brain herniationBrain herniationBrain herniation, also known as cistern obliteration, is a deadly side effect of very high intracranial pressure that occurs when the brain shifts across structures within the skull...
- Intracranial hemorrhageIntracranial hemorrhageAn intracranial hemorrhage is a hemorrhage, or bleeding, within the skull.-Causes:Intracranial bleeding occurs when a blood vessel within the skull is ruptured or leaks. It can result from physical trauma or nontraumatic causes such as a ruptured aneurysm...
- Intracranial pressureIntracranial pressureIntracranial pressure is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid . The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by about 1 mmHg in normal adults through shifts in production and absorption of CSF...
- Penetrating traumaPenetrating traumaPenetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out...
- Traumatic brain injuryTraumatic brain injuryTraumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...
- Head injuryHead injuryHead injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....
- Skull fractureSkull fractureA skull fracture is a break in one or more of the bones in the skull usually occurring as a result of blunt force trauma. If the force of the impact is excessive the bone may fracture at or near the site of the impact...