Head injury
A head injury is any injury that results in trauma to the skull or brain. The terms traumatic brain injury and head injury are often used interchangeably in the medical literature. Because head injuries cover such a broad scope of injuries, there are many causes—including accidents, falls, physical assault, or traffic accidents—that can cause head injuries.
The number of new cases is 1.7 million in the United States each year, with about 3% of these incidents leading to death. Adults have head injuries more frequently than any age group resulting from falls, motor vehicle crashes, colliding or being struck by an object, or assaults. Children, however, may experience head injuries from accidental falls or intentional causes leading to hospitalization. Acquired brain injury is a term used to differentiate brain injuries occurring after birth from injury, from a genetic disorder, or from a congenital disorder.
Unlike a broken bone where trauma to the body is obvious, head trauma can sometimes be conspicuous or inconspicuous. In the case of an open head injury, the skull is cracked and broken by an object that makes contact with the brain. This leads to bleeding. Other obvious symptoms can be neurological in nature. The person may become sleepy, behave abnormally, lose consciousness, vomit, develop a severe headache, have mismatched pupil sizes, and/or be unable to move certain parts of the body. While these symptoms happen immediately after a head injury occurs, many problems can develop later in life. Alzheimer's disease, for example, is much more likely to develop in a person who has experienced a head injury.
Brain damage, which is the destruction or degeneration of brain cells, is a common occurrence in those who experience a head injury. Neurotoxicity is another cause of brain damage that typically refers to selective, chemically induced neuron/brain damage.
Classification
Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull. Head injuries can be closed or open. A closed head injury is where the dura mater remains intact. The skull can be fractured, but not necessarily. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area. A head injury may cause skull fracture, which may or may not be associated with injury to the brain. Some patients may have linear or depressed skull fractures. If intracranial hemorrhage occurs, a hematoma within the skull can put pressure on the brain. Types of intracranial hemorrhage include subdural, subarachnoid, extradural, and intraparenchymal hematoma. Craniotomy surgeries are used in these cases to lessen the pressure by draining off the blood.Brain injury can occur at the site of impact, but can also be at the opposite side of the skull due to a contrecoup effect. While impact on the brain at the same site of injury to the skull is the coup effect. If the impact causes the head to move, the injury may be worsened, because the brain may ricochet inside the skull causing additional impacts, or the brain may stay relatively still but be hit by the moving skull.
Specific problems after head injury can include
Concussion
A concussion is a form of a mild traumatic brain injury. This injury is a result due to a blow to the head that could make the person's physical, cognitive, and emotional behaviors irregular. Symptoms may include clumsiness, fatigue, confusion, nausea, blurry vision, headaches, and others. Mild concussions are associated with sequelae. Severity is measured using various concussion grading systems.A slightly greater injury is associated with both anterograde and retrograde amnesia. The amount of time that the amnesia is present correlates with the severity of the injury. In all cases, the patients develop post concussion syndrome, which includes memory problems, dizziness, tiredness, sickness and depression. Cerebral concussion is the most common head injury seen in children.
Intracranial bleeding
Types of intracranial hemorrhage are roughly grouped into intra-axial and extra-axial. The hemorrhage is considered a focal brain injury; that is, it occurs in a localized spot rather than causing diffuse damage over a wider area.Intra-axial bleeding
Intra-axial hemorrhage is bleeding within the brain itself, or cerebral hemorrhage. This category includes intraparenchymal hemorrhage, or bleeding within the brain tissue, and intraventricular hemorrhage, bleeding within the brain's ventricles. Intra-axial hemorrhages are more dangerous and harder to treat than extra-axial bleeds.Extra-axial bleeding
Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:- Epidural hemorrhage which occur between the dura mater and the skull, is caused by trauma. It may result from laceration of an artery, most commonly the middle meningeal artery. This is a very dangerous type of injury because the bleed is from a high-pressure system and deadly increases in intracranial pressure can result rapidly. However, it is the least common type of meningeal bleeding and is seen in 1% to 3% cases of head injury.
- * Patients have a loss of consciousness, then a lucid interval, then sudden deterioration
- * Head CT shows lenticular deformity.
- Subdural hemorrhage results from tearing of the bridging veins in the subdural space between the dura and arachnoid mater.
- * Head CT shows crescent-shaped deformity
- Subarachnoid hemorrhage, which occur between the arachnoid and pia meningeal layers, like intraparenchymal hemorrhage, can result either from trauma or from ruptures of aneurysms or arteriovenous malformations. Blood is seen layering into the brain along sulci and fissures, or filling cisterns. The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache. This can be a very dangerous entity and requires emergent neurosurgical evaluation and sometimes urgent intervention.
Cerebral contusion
Diffuse axonal injury
, or DAI, usually occurs as the result of an acceleration or deceleration motion, not necessarily an impact. Axons are stretched and damaged when parts of the brain of differing density slide over one another. Prognoses vary widely depending on the extent of the damage.Compound head injury
Overlying scalp laceration and soft tissue disruption in continuity with a skull fracture constitutes "compound head injury", and has higher rates of infection, unfavorable neurologic outcome, delayed seizures, mortality, and duration of hospital stay.Signs and symptoms
Three categories used for classifying the severity of brain injuries are mild, moderate or severe.Mild brain injuries
Symptoms of a mild brain injury include headaches, confusion, ringing ears, fatigue, changes in sleep patterns, mood or behavior. Other symptoms include trouble with memory, concentration, attention or thinking. Mental fatigue is a common debilitating experience and may not be linked by the patient to the original incident. Narcolepsy and sleep disorders are common misdiagnoses.Moderate/severe brain injuries
Cognitive symptoms include confusion, aggression, abnormal behavior, slurred speech, and coma or other disorders of consciousness. Physical symptoms include headaches that do not go away or worsen, vomiting or nausea, convulsions or seizures, abnormal dilation of the eyes, inability to awaken from sleep, weakness in the extremities, and a loss of coordination. In cases of severe brain injuries, the likelihood of areas with permanent disability is great, including neurocognitive deficits, delusions, speech or movement problems, and intellectual disability. There may also be personality changes. The most severe cases result in coma or even persistent vegetative state.Symptoms in children
Symptoms observed in children include changes in eating habits, persistent irritability or sadness, changes in attention, disrupted sleeping habits, or loss of interest in toys.Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without neurological deficit. Patients with concussion may have a history of seconds to minutes unconsciousness, then normal arousal. Disturbance of vision and equilibrium may also occur. Common symptoms of head injury include coma, confusion, drowsiness, personality change, seizures, nausea and vomiting, headache and a lucid interval, during which a patient appears conscious only to deteriorate later.
Symptoms of skull fracture can include:
- leaking cerebrospinal fluid is strongly indicative of basilar skull fracture and the tearing of sheaths surrounding the brain, which can lead to secondary brain infection.
- visible deformity or depression in the head or face; for example a sunken eye can indicate a maxillar fracture
- an eye that cannot move or is deviated to one side can indicate that a broken facial bone is pinching a nerve that innervates eye muscles
- wounds or bruises on the scalp or face.
- Basilar skull fractures, those that occur at the base of the skull, are associated with Battle's sign, a subcutaneous bleed over the mastoid, hemotympanum, and cerebrospinal fluid rhinorrhea and otorrhea.
The Glasgow Coma Scale is a tool for measuring the degree of unconsciousness and is thus a useful tool for determining the severity of the injury. The Pediatric Glasgow Coma Scale is used in young children. The widely used PECARN Pediatric Head Injury/Trauma Algorithm helps physicians weigh risk-benefit of imaging in a clinical setting given multiple factors about the patient—including mechanism/location of the injury, age of the patient, and GCS score.