Head injury

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Head injury
Other names	Head trauma
cerebral hemorrhage, stroke, coma, nervous system damage, paralysis, death
Types	Concussion, cerebral contusion, penetrating head injury, basilar skull fracture, traumatic brain 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.^[1] 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 (such as being struck or shaken) leading to hospitalization.

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.^[3]

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

surgeries are used in these cases to lessen the pressure by draining off the blood.

effect (the impact to the head can cause the brain to move within the skull, causing the brain to impact the interior of the skull opposite the head-impact). 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 (due to inertia) but be hit by the moving skull (both are contrecoup injuries).

Specific problems after head injury can include[4]^[5][6]

Concussion

Coup injury

A concussion is a form of a mild traumatic brain injury (TBI). 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,

.

A slightly greater injury is associated with both anterograde and retrograde

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

Extra-axial bleeding

Comparison of epidural and subdural hematomas

• v
• t
• e

Compared quality	Epidural	Subdural
Location	Between the endosteal and inner meningeal layer of dura mater	Between the meningeal layers of dura mater and the Arachnoid mater
Involved vessel	Temperoparietal locus (most likely) – transverse or sigmoid sinuses Vertex locus – superior sagittal sinus	Bridging veins
Symptoms (depending on the severity)[11]	Lucid interval followed by unconsciousness	Gradually increasing headache and confusion
CT scan appearance	Biconvex lens	Crescent-shaped

Extra-axial hemorrhage, bleeding that occurs within the skull but outside of the brain tissue, falls into three subtypes:

• meninx) 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 (LOC), then a lucid interval, then sudden deterioration (vomiting, restlessness, LOC)
  • Head CT shows lenticular (convex) 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
• cisterns (most often the suprasellar cistern because of the presence of the vessels of the circle of Willis and their branch points within that space). The classic presentation of subarachnoid hemorrhage is the sudden onset of a severe headache (a thunderclap headache
  ). This can be a very dangerous entity and requires emergent neurosurgical evaluation and sometimes urgent intervention.

Cerebral contusion

Cerebral contusion is bruising of the brain tissue. The piamater is not breached in contusion in contrary to lacerations. The majority of contusions occur in the frontal and temporal lobes. Complications may include cerebral edema and transtentorial herniation. The goal of treatment should be to treat the increased intracranial pressure. The prognosis is guarded.

Diffuse axonal injury

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.^[12]

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 (minor) incident. Narcolepsy and sleep disorders are common misdiagnoses.^{[citation needed]}

Moderate/severe brain injuries

Cognitive symptoms include confusion, aggressive, 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 loss of coordination. In cases of severe brain injuries, the likelihood of areas with permanent

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.[13]

Presentation varies according to the injury. Some patients with head trauma stabilize and other patients deteriorate. A patient may present with or without

Symptoms of skull fracture can include:

• leaking cerebrospinal fluid (a clear fluid drainage from nose, mouth or ear) 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.
• otorrhea
  .

Because brain injuries can be life-threatening, even people with apparently slight injuries, with no noticeable signs or complaints, require close observation; They have a chance for severe symptoms later on. The caretakers of those patients with mild trauma who are released from the hospital are frequently advised to rouse the patient several times during the next 12 to 24 hours to assess for worsening symptoms.

The

Location of brain damage predicts symptoms

Symptoms of brain injuries can also be influenced by the location of the injury and as a result, impairments are specific to the part of the brain affected. Lesion size is correlated with severity, recovery, and comprehension.[16] Brain injuries often create impairment or disability that can vary greatly in severity.

Studies show there is a correlation between brain lesion and language, speech, and category-specific disorders. Wernicke's aphasia is associated with

Damage to the Broca's area typically produces symptoms like omitting functional words (agrammatism), sound production changes, dyslexia, dysgraphia, and problems with comprehension and production. Broca's aphasia is indicative of damage to the posterior inferior frontal gyrus of the brain.^[19]

An impairment following damage to a region of the brain does not necessarily imply that the damaged area is wholly responsible for the cognitive process which is impaired, however. For example, in pure alexia, the ability to read is destroyed by a lesion damaging both the left visual field and the connection between the right visual field and the language areas (Broca's area and Wernicke's area). However, this does not mean someone with pure alexia is incapable of comprehending speech—merely that there is no connection between their working visual cortex and language areas—as is demonstrated by the fact that pure alexics can still write, speak, and even transcribe letters without understanding their meaning.^[20] Lesions to the fusiform gyrus often result in prosopagnosia, the inability to distinguish faces and other complex objects from each other.^{[21][medical citation needed][22]} Lesions in the amygdala would eliminate the enhanced activation seen in occipital and fusiform visual areas in response to fear with the area intact. Amygdala lesions change the functional pattern of activation to emotional stimuli in regions that are distant from the amygdala.^[23]

Other lesions to the

, a loss of perception on the opposite side of the body.

Causes

Head injuries can be caused by a large variety of reasons. All of these causes can be put into two categories used to classify head injuries; those that occur from impact (blows) and those that occur from shaking.

According to the United States

Brain tumors

can increase intracranial pressure, causing brain damage.

Diagnosis

There are a few methods used to diagnose a head injury. A healthcare professional will ask the patient questions revolving around the injury as well as questions to help determine in what ways the injury is affecting function. In addition to this hearing, vision, balance, and reflexes may also be assessed as an indicator of the severity of the injury.^[29] A non-contrast CT of the head should be performed immediately in all those who have sustained a moderate or severe head injury. A CT is an imaging technique that allows physicians to see inside the head without surgery in order to determine if there is internal bleeding or swelling in the brain.^[31] Computed tomography (CT) has become the diagnostic modality of choice for head trauma due to its accuracy, reliability, safety, and wide availability. The changes in microcirculation, impaired auto-regulation, cerebral edema, and axonal injury start as soon as a head injury occurs and manifest as clinical, biochemical, and radiological changes.^[32] An MRI may also be conducted to determine if someone has abnormal growths or tumors in the brain or to determine if the patient has had a stroke.^[33]

Glasgow Coma Scale (GCS) is the most widely used scoring system used to assess the level of severity of a brain injury. This method is based on objective observations of specific traits to determine the severity of a brain injury. It is based on three traits eye-opening, verbal response, and motor response, gauged as described below. Based on the Glasgow Coma Scale severity is classified as follows, severe brain injuries score 3–8, moderate brain injuries score 9-12 and mild score 13–15.

There are several imaging techniques that can aid in diagnosing and assessing the extent of brain damage, such as

(PET), single-photon emission tomography (SPECT). CT scans and MRI are the two techniques widely used and are the most effective. CT scans can show brain bleeds, fractures of the skull, fluid build up in the brain that will lead to increased cranial pressure. MRI is able to better detect smaller injuries, detect damage within the brain, diffuse axonal injury, injuries to the brainstem, posterior fossa, and subtemporal and sub frontal regions. However, patients with pacemakers, metallic implants, or other metal within their bodies are unable to have an MRI done. Typically the other imaging techniques are not used in a clinical setting because of the cost, lack of availability.

Management

Most head injuries are of a benign nature and require no treatment beyond

. If the brain has been severely damaged by trauma, a neurosurgical evaluation may be useful. Treatments may involve controlling elevated intracranial pressure. This can include sedation, paralytics, cerebrospinal fluid diversion. Second-line alternatives include decompressive craniectomy (Jagannathan et al. found a net 65% favorable outcomes rate in pediatric patients), barbiturate coma, hypertonic saline, and hypothermia. Although all of these methods have potential benefits, there has been no randomized study that has shown unequivocal benefit.

Clinicians will often consult clinical decision support rules such as the Canadian CT Head Rule or the New Orleans/Charity Head injury/Trauma Rule to decide if the patient needs further imaging studies or observation only. Rules like these are usually studied in depth by multiple research groups with large patient cohorts to ensure accuracy given the risk of adverse events in this area.^[34]

There is a subspecialty certification available for brain injury medicine that signifies expertise in the treatment of brain injury.^[35][36]

Prognosis

Prognosis, or the likely progress of a disorder, depends on the nature, location, and cause of the brain damage (see Traumatic brain injury, Focal and diffuse brain injury, Primary and secondary brain injury).

In children with uncomplicated minor head injuries the risk of intracranial bleeding over the next year is rare at 2 cases per 1 million.^[37] In some cases transient neurological disturbances may occur, lasting minutes to hours. Malignant post traumatic cerebral swelling can develop unexpectedly in stable patients after an injury, as can post-traumatic seizures. Recovery in children with neurologic deficits will vary. Children with neurologic deficits who improve daily are more likely to recover, while those who are vegetative for months are less likely to improve. Most patients without deficits have full recovery. However, persons who sustain head trauma resulting in unconsciousness for an hour or more have twice the risk of developing Alzheimer's disease later in life.^[38]

Head injury may be associated with a neck injury. Bruises on the back or neck, neck pain, or pain radiating to the arms are signs of cervical spine injury and merit spinal immobilization via application of a

, one-sided weakness, or has persistent vomiting.

To combat overuse of head CT scans yielding negative intracranial hemorrhage results, which unnecessarily exposes patients to radiation and increase time in the hospital and cost of the visit, multiple clinical decision support rules have been developed to help clinicians weigh the option to scan a patient with a head injury. Among these are the Canadian Head CT rule, the PECARN Head Injury/Trauma Algorithm, and the New Orleans/Charity Head Injury/Trauma Rule all help clinicians make these decisions using easily obtained information and noninvasive practices.

Brain injuries are very hard to predict in the outcome. Many tests and specialists are needed to determine the likelihood of the prognosis. People with minor brain damage can have debilitating side effects; not just severe brain damage has debilitating effects. The side-effects of a brain injury depend on location and the body's response to injury. Even a mild concussion can have long term effects that may not resolve.

History

The foundation for understanding human behavior and brain injury can be attributed to the case of Phineas Gage and the famous case studies by Paul Broca. The first case study on Phineas Gage's head injury is one of the most astonishing brain injuries in history. In 1848, Phineas Gage was paving way for a new railroad line when he encountered an accidental explosion of a tamping iron straight through his frontal lobe. Gage observed to be intellectually unaffected but exemplified post-injury behavioral deficits. These deficits include: becoming sporadic, disrespectful, extremely profane, and gave no regard for other workers. Gage started having seizures in February 1860, dying only four months later on May 21, 1860.^[39]

Ten years later, Paul Broca examined two patients exhibiting impaired speech due to frontal lobe injuries. Broca's first patient lacked productive speech. He saw this as an opportunity to address language localization. It wasn't until Leborgne, formally known as "tan", died when Broca confirmed the frontal lobe lesion from an autopsy. The second patient had similar speech impairments, supporting his findings on language localization. The results of both cases became a vital verification of the relationship between speech and the left cerebral hemisphere. The affected areas are known today as Broca's area and Broca's Aphasia.^[40]

A few years later, a German neuroscientist, Carl Wernicke, consulted on a stroke patient. The patient experienced neither speech nor hearing impairments but had a few brain deficits. These deficits included: lacking the ability to comprehend what was spoken to him and the words written down. After his death, Wernicke examined his autopsy that found a lesion located in the left temporal region. This area became known as Wernicke's area. Wernicke later hypothesized the relationship between Wernicke's area and Broca's area, which was proven fact.^[41]

Epidemiology

Head injury is the leading cause of death in many countries.^[42]

See also

• Traumatic brain injury
• Brain damage
• Concussion
• Acquired brain injury
• Neurodegeneration
• Chronic traumatic encephalopathy

References

External links

• Brain Injury (journal)
• Cochrane Injuries Group: systematic reviews on the prevention, treatment and rehabilitation of traumatic injury
• First aid advice for head injuries Archived 2011-05-19 at the Wayback Machine from the British Red Cross