1. Introduction

Head injury is physical injury to brain tissue that temporarily or permanently impairs

brain function.  Loss of consciousness does not need to occur. The severity of head

injuries is most commonly classified by the initial post-resuscitation of Glasgow Coma

Scale (GCS) score, which generates a numerical summed score for eye, motor, and verbal

abilities. Traditionally, a score of 13-15 indicates mild injury, a score of 9-12 indicates

moderate injury, and a score of 8 or less indicates severe injury. Head injury is classified

as either closed or open (penetrating). A closed head injury means you received a hard

blow to the head from striking an object, but the object did not break the skull. While an

open, or penetrating, head injury means you were hit with an object that broke the skull

and entered the brain. This usually happens when you move at high speed, such as going

through the windshield during a car accident. It can also happen from a gunshot to the

head.

2. Classification 

2.1 Hematoma

Hematomas (collections of blood in or around the brain) can occur with open or closed

injuries and may be epidural, subdural, or intracerebral. Subarachnoid hemorrhage is

common in head injury, although the appearance on CT scan is not usually the same as

aneurysmal Subarachnoid hemorrhage.

2.2 Subdural hematoma

Subdural hematomas are collections of blood between the dura mater and the pia-

arachnoid mater. Acute subdural hematomas arise from laceration of cortical veins or

avulsion of bridging veins between the cortex and dural sinuses. They often occur with

head trauma from falls and motor vehicle crashes. Compression of the brain by the

hematoma and swelling of the brain due to edema or hyperemia (increased blood flow

due to engorged blood vessels) can increase ICP. When these processes both occur,

mortality and morbidity can be high. A chronic subdural hematoma may appear and

produce symptoms gradually over several weeks after trauma.These hematomas occur

more often in elderly patients (especially in those taking antiplatelet or anticoagulant

drugs, or in those with brain atrophy). Elderly patients may consider the head injury

relatively trivial or may have even forgotten it.

2.3 Epidural hematoma

With an epidural hematoma, the bleeding is located between the dura mater and the skull.

This is often present along the side of the head where the middle meningeal  artery runs in

a groove along the temporal bone. This bone is relatively thin and offers less protection

of the skull. As the bleeding continues, the hematoma expands. There is little space in the

skull for the hematoma to grow and as it expands, the adjacent brain tissue is compressed.

As the pressure increases, the whole brain begins to shift and becomes compressed

against the bones of the skull. The pressure tends to build quickly because the septae that

attach the dura to the skull bones create small spaces that trap blood.

2.4 Subarachnoid bleed

Subarachnoid bleeding occurs in the space beneath the arachnoid layer where the CSF is

located. Often there is intense headache and vomiting with subarachnoid bleeding.

Because this space connects with the spinal canal, pressure build-up tends not to occur.

However, this injury often occurs in combination with the other types of bleeding in the

brain, and the symptoms can be compounded.

2.5 Intracerebral bleed

Intracerebral bleeding occurs within the brain tissue itself. Sometimes the amount of

bleeding is small, but like bruising in any other part of the body, swelling or edema may

occur over a period of time, causing a progressive decrease in the level of consciousness

and other symptoms of head injury.

2.6 Skull fracture

The bones of the skull are classified as flat bones, meaning that they do not have an

inside marrow. It takes a significant amount of force to break the skull, and the skull does

not absorb any of that impact. It is often transmitted directly to the brain. Skull fractures

are described by which bone is broken, whether there is an associated laceration of the

scalp, and whether the bone is depressed and potentially pushed into the brain tissue.

2.7 Concussion 

Concussion is defined as a transient and reversible post traumatic alteration in mental

status (eg, loss of consciousness or memory) lasting from seconds to minutes and, by

arbitrary definition, < 6 h. Gross structural brain lesions and serious neurologic residual

are not part of concussion, although temporary disability can occur due to symptoms,

such as nausea, headache, dizziness, and memory disturbance (post concussion

syndrome).

2.8 Brain contusions 

Contusions (bruises of the brain) can occur with open or closed injuries and can impair a

wide range of brain functions, depending on contusion size and location. Larger

contusions may cause brain edema and increased intracranial pressure (ICP). Contusions

may enlarge in the hours and days following the initial injury and cause neurologic

deterioration.

2.9 Diffuse axonal injury

Diffuse axonal injury (DAI) occurs when deceleration causes shear-type forces that result

in generalized, widespread disruption of axonal fibers and myelin sheaths. A few DAI

lesions may also result from minor head injury. Gross structural lesions are not part of

DAI, but small petechial hemorrhages in the white matter are often observed on CT scan

and on histopathologic examination. DAI is sometimes defined clinically as a loss of

consciousness lasting > 6 h in the absence of a specific focal lesion. Edema from the

injury often increases ICP, leading to various manifestations. DAI is typically the

underlying injury in shaken baby syndrome.

Common Types of Traumatic Brain Injury

Disorder Clinical Findings Diagnosis

Acute subdural hematoma Typically, acute neurologic

dysfunction, which may be

focal, nonfocal, or both

Patients with small

hematomas may have normal

function

CT: Hyperdensity in subdural

space, classically crescent-

shaped

Degree of midline shift

important

Basilar skull fracture Leakage of CSF from the nose

or ear

Blood behind the tympanic

membrane (hemotympanum)

or in the external ear

Ecchymosis behind the ear

(Battle's sign) or around the

eye (raccoon eyes)

CT: Usually visible

Brain contusion Widely variable degrees of

neurologic dysfunction or

normal function

CT: Hyperdensities resulting

from punctate hemorrhages

of varied sizes

Concussion Transient mental status

alteration (eg, loss of

consciousness or memory)

lasting < 6 h

Based on clinical findings

CT or MRI: Clinical

abnormalities not explained

by lesions in brain

parenchyma

Chronic subdural hematoma Gradual headache,

somnolence, confusion,

sometimes with focal deficits

or seizures

CT: Hypodensity in subdural

space (abnormality is

isodense during subacute

transition from hyperdense to

hypodense)

Diffuse axonal injury Loss of consciousness lasting

> 6 h but may not have focal

deficits or motor posturing

Based on clinical findings

CT: At first, may be normal or

show small hyperdensities

(microhemorrhages) in corpus

callosum, centrum semiovale,

basal ganglia, or brain stem

MRI: Often abnormal

Epidural hematoma Headache, impaired

consciousness within hours,

sometimes with a lucid

interval

Herniation typically causing

contralateral hemiparesis and

ipsilateral pupillary dilation

CT: Hyperdensity in epidural

space, classically lenticular-

shaped and located over the

middle meningeal artery

(temporal fossa) due to a

temporal bone fracture

Subarachnoid hemorrhage Typically, normal function

Occasionally, acute neurologic

dysfunction

CT: Hyperdensity within

subarachnoid space on the

surface of the brain; often

outlining sulci

3. Etiology

By definition, trauma is required to cause a head injury, but that trauma does not

necessarily need to be violent. Falling down a few steps or falling into a hard object may

be enough to cause damage. Motor vehicle crashes account for more than 50% of

traumatic brain injuries, with sports related injuries mostly football adding another 20%.

Almost 80% of head injuries occur in males.

3.1 Penetrating trauma

Missiles such as bullets or sharp instruments (such as knives, screwdrivers, or ice picks)

may penetrate the skull. The result is called a penetrating head injury. Penetrating injuries

often require surgery to remove debris from the brain tissue. The initial injury itself may

cause immediate death, especially if from a high-energy missile such as a bullet. 

3.2 Blunt head trauma 

These injuries may be from a direct blow (a club or large missile) or from a rapid

deceleration force (a fall or striking the windshield in a car accident).

4. Pathophysiology

Brain function may be immediately impaired by direct damage (crush, laceration) of

brain tissue. Further damage may occur shortly from the cascade of events triggered by

the initial injury. Head injury of any sort can produce cerebral edema and decrease brain

blood flow. The cranial vault is fixed in size (constrained by the skull) and filled by CSF

and minimally compressible brain tissue, consequently, any swelling from edema or an

intracranial hematoma has nowhere to expand and thus increases ICP. Cerebral blood

flow is proportional to the cerebral perfusion pressure (CPP), which is the difference

between mean arterial pressure (MAP) and mean ICP. Thus, as ICP increases, CPP

decreases. When CCP falls below 50 mm Hg, the brain may become ischemic. Ischemia

and edema may trigger various secondary mechanisms of injury (eg, release of excitatory

neurotransmitters, intracellular Ca, free radicals, and cytokines), causing further cell

damage, further edema, and further increases in ICP. Systemic complications from

trauma (eg, hypotension, hypoxia) can also contribute to cerebral ischemia and are often

called secondary brain insults. Excessive ICP initially causes global cerebral dysfunction.

If excessive ICP is unrelieved, it can push brain tissue across the tentorium or through the

foramen magnum, causing herniation and increased morbidity and mortality.

5. Symptoms

Signs and symptoms of head injuries vary with the type and severity of the injury.

Symptoms can vary from almost none to loss of consciousness and coma. As well, the

symptoms may not necessarily occur immediately at the time of injury. While a brain

injury occurs at the time of trauma, it may take time for enough swelling or bleeding to

occur to cause symptoms that are recognizable. Minor blunt head injuries may involve

only symptoms of being "dazed" or brief loss of consciousness. They may result in

headaches or blurring of vision or nausea and vomiting.There may be longer lasting

subtle symptoms including, irritability, difficulty concentrating, insomnia, and difficulty

tolerating bright light and loud sounds. These post concussion symptoms may last for a

prolonged period of time. Severe blunt head trauma involves a loss of consciousness

lasting from several minutes to many days or longer. Seizures may result. The person

may suffer from severe and sometimes permanent neurological deficits or may die.

Neurological deficits from head trauma resemble those seen in stroke and

include paralysis, seizures, or difficulty with speaking, seeing, hearing, walking, or

understanding. While in penetrating trauma may cause immediate, severe symptoms or

only minor symptoms despite a potentially life-threatening injury. Death may follow

from the initial injury. Any of the signs of serious blunt head trauma may result.

6. Diagnosis

The physician or health care practitioner will take a history of the events. The

information may be provided by the patient, people who witnessed the event, emergency

medical personnel, and if applicable, the police. The circumstances are very important

since it is important to find out the severity and intensity of the trauma sustained by the

head. If the patient is not fully awake, the examination will initially try to determine the

level of coma using the Glasgow Coma Scale (GCS) which number is useful in tracking

whether the patient is improving or declining in function over time. If no other injuries

are found on examining the body, attention will be paid to the head and the neurologic

exam. The health care practitioner will examine the patient for evidence of a basilar

skull fracture, in which an injury has occurred to the bones that support the brain. Signs

of this type of fracture include bruising of around the eyes (called raccoon eyes),  bruising

behind the ear (Battle's sign), bleeding from the ear canal, or CSF leaking from the ear or

nose. The neurologic exam may include evaluation of the cranial nerves. If the neck is

not injured, the exam may include evaluation of muscle tone and strength of the arms and

legs; sensation in the extremities including light touch, pain, and vibration; coordination;

and walking. It is important to remember that injuries to other parts of the body may also

be present, and the evaluation of the head injury may occur at the same time as the

evaluation of other injuries.

 Imaging should always be done in patients with more than transiently impaired

consciousness, GCS score < 15, focal neurologic findings, persistent vomiting, seizures, a

history of loss of consciousness or clinically suspected fractures. However, a case can be

made for obtaining a CT scan of the head in all patients with more than a trivial head

injury, because the clinical and medicolegal consequences of missing a hematoma are

severe. MRI may be useful later in the clinical course to detect more subtle contusions

and DAI. It is usually more sensitive than CT for the diagnosis of very small acute or

isodense subacute and isodense chronic subdural hematomas. Preliminary, unconfirmed

evidence suggests that certain MRI findings predict prognosis.

7. Treatment

Multiple noncranial injuries, which are likely with motor vehicle crashes and falls, often

require simultaneous treatment. At the injury scene, a clear airway is secured and external

bleeding is controlled before the patient is moved. Particular care is taken to avoid

displacement of the spine or other bones to protect the spinal cord and blood vessels.

Proper immobilization should be maintained with a cervical collar and long spine board

until stability of the entire spine has been established by appropriate examination and

imaging. After the initial rapid neurologic assessment, pain should be relieved with a

short-acting opioid. In the hospital, after quick initial evaluation, neurologic findings

(GCS and pupillary reaction), BP, pulse, and temperature should be recorded frequently

for several hours because any deterioration demands prompt attention. Serial GCS and CT

results stratify injury severity.

7.1 Mild injury

 Injury is mild (by GCS score) in 80% of patients who have head injury and present to an

emergency department. If there is brief or no loss of consciousness and if patients have

stable vital signs, a normal head CT scan, and normal mental and neurologic function,

they may be discharged home provided family members or friends can observe them

closely for an additional 24 h. These observers are instructed to return patients to the

hospital if any of the following develop: decreased level of consciousness, focal

neurologic deficits, worsening headache, vomiting, or deterioration of mental function.

Patients who have had loss of consciousness or have any abnormalities in mental or

neurologic function and cannot be observed closely after discharge are generally

observed in the emergency department or overnight in the hospital and follow-up CT is

done in 4 to 8 h. Patients who have no neurologic changes but minor abnormalities on

head CT (eg, small contusions, small subdural hematomas with no mass effect, or

punctuate or small traumatic subarachnoid hemorrhage) may need only a follow-up CT

within 24 h. With a stable CT and normal neurologic examination results, these patients

may be discharged home.

7.2 Moderate and severe injury

Injury is moderate in 10% of patients who have head injury and present to an emergency

department. They often do not require intubation and mechanical ventilation (unless other

injuries are present) or ICP monitoring. However, because deterioration is possible, these

patients should be admitted and observed even if head CT is normal.

Injury is severe in 10% of patients who have head injury and present to an emergency

department. They are admitted to a critical care unit. Because airway protective reflexes

are usually impaired and ICP may be increased, patients are intubated endotracheally

while measures are taken to avoid increasing ICP. Close monitoring using the GCS and

pupillary response should continue, and CT scan is repeated, particularly if there is an

unexplained ICP rise. Osmotic diuretics (eg, mannitol) may be given IV to lower ICP and

maintain serum osmolality.

7.3 Surgery

 Intracranial hematomas may require urgent surgical evacuation to prevent or treat brain

shift, compression, and herniation; hence, early neurosurgical consultation is mandatory.

However, not all hematomas require surgical removal. Small intracerebral hematomas

rarely require surgery. Patients with small subdural hematomas can often be treated

without surgery. Factors that suggest a need for surgery include a midline brain shift

of > 5 mm, compression of the basal cisterns, and worsening neurologic examination

findings. Chronic subdural hematomas may require surgical drainage but much less

urgently than acute subdural hematomas. Large or arterial epidural hematomas are treated

surgically, but small epidural hematomas that are thought to be venous in origin can be

followed with serial CT scans.

7.4 Rehabilitation

 When neurologic deficits persist, rehabilitation is needed. Rehabilitation is best provided

through a team approach that combines physical, occupational, and speech therapy, skill-

building activities, and counseling to meet the patient's social and emotional needs. Brain

injury support groups may provide assistance to the families of brain-injured patients.

8. Prognosis

Adults with severe head injury who are treated have a mortality rate of about 25 to 33%.

Mortality is lower with higher GCS scores. Mortality rates are lower in children ≥ 5 yr

(≤10% with a GCS score of 5 to 7). Children overall do better than adults with a

comparable injury. The vast majority of patients with mild head injury retain good

neurologic function. With moderate or severe head injury, the prognosis is not as good

but is much better than is generally believed. There are indications for head injury

outcome:

Good recovery (return to previous level of function)

Moderate disability (capable of self-care)

Severe disability (incapable of self-care)

Vegetative (no cognitive function)

Death

Over 50% of adults with severe head injury have a good recovery or moderate disability.

Occurrence and duration of coma after a head injury are strong predictors of disability.

Of patients whose coma exceeds 24 h, 50% have major persistent neurologic sequelae,

and 2 to 6% remain in a persistent vegetative state at 6 mo. In adults with severe head

injury, recovery occurs most rapidly within the initial 6 mo. Smaller improvements

continue for perhaps as long as several years. Children have a better immediate recovery

from head injury regardless of severity and continue to improve for a longer period of

time. Cognitive deficits, with impaired concentration, attention, and memory, and various

personality changes are a more common cause of disability in social relations and

employment than are focal motor or sensory impairments. Posttraumatic anosmia and

acute traumatic blindness seldom resolve after 3 to 4 mo. Hemiparesis and aphasia

usually resolve at least partially, except in the elderly.

9. Prevention

In sporting activities, the use of a helmet may help minimize the risk of injury; similarly,

wearing a helmet while riding a motorcycle or bicycle helps minimize the risk of brain

injury. Seatbelts can help prevent a head injury during a car crash. Since alcohol is a risk

factor for falls and other injuries, it should be used responsibly. Falls are a concern in the

elderly. Homes can be made less fall-prone by installing assist devices on walls and in

bathrooms. Loose floor coverings such as area rugs should be avoided, since walking

from one floor covering to another increases the risk of falls. If needed, canes and

walkers may be helpful as walking assistive devices.

References

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from:http://www.merckmanuals.com/professional/sec21/ch310/ch310a.html

[Accessed 10 April 2011]

Benjamin, C. 2010. Head Injury, Medicinenet website, Available from :

http://www.medicinenet.com/head_injury/article.htm [Accessed 11 April 2011]

David , A. 2009. Head Injury, Emedicine website, Avalaible from :

http://emedicine.medscape.com/article/1163653-overview

[Accessed 11 April 2011]

Kumar P, Clark M. 2002. Clinical Medicine 5th Edition. Head Injury.

WB Saunders. P 1175-1176

Tortora G, Derrickson B. 2006. Principles of Anatomy and physiology 11th Edition.

The Brain and Cranial Nerves. John Wiley & sons,Inc. P 496