Understanding Brain Injury - Acute Hospitalization

Understanding Brain Injury > Understanding Brain Injury - Acute Hospitalization

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Brain Injuries

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The term brain injury is often used interchangeably with head injury.  However, brain injury is a more specific term. Most traumatic brain injuries occur in association with accidents or physical assaults that result in a forceful blow to the head, yet injury to the brain can occur in other ways. A near drowning victim revived through cardiopulmonary resuscitation suffers damage to brain cells because of lack of oxygen. A stroke occurs when a brain blood vessel ruptures or becomes clogged, and the blood supply (carrying oxygen and nutrients) is interrupted, resulting in injury to the brain tissue. Likewise, bleeding from a ruptured artery underneath the skull or within the brain can compress brain tissue and lead to permanent damage and or temporary loss of brain function. Infections, such as meningitis, brain tumors, an overdose of medications, and certain diseases can also result in injury to the brain. 

The changes that occur after a brain injury depend on the severity, type and location of the damage. Physical, emotional, mental, and behavioral changes can be temporary or long-lasting. Since no part of the brain operates independently, an injury in one area often affects the functions of many brain areas simultaneously. Interactions between different parts of the brain are essential for almost all body functions. Fortunately when one part of the brain fails to operate properly, other parts may eventually compensate for the loss. Recovery following a brain injury can take a great deal of time and may be partial or complete. 

To better understand the effects of brain injury, the causes and types are outlined on the following pages.



A concussion is a common term used to describe a mild brain injury. Signs that may briefly follow trauma indicating a concussion include: confusion, amnesia, slurred speech, headache, dizziness, nausea, vomiting, as well as loss of balance or loss of consciousness. A major misconception is that a concussion only occurs when an individual is “knocked out”. The majority of concussions do not involve loss of consciousness.  Usually the more intense the blow, the more severe the concussion and the resulting symptoms. Lingering symptoms that follow a concussion may include difficulties with headaches, dizziness, vision, hearing, tasting, smelling, balance, coordination, sleep regulation, fatigue, sensation, cognition and emotional regulation.


Skull Fractures 

All skull fractures are associated with a risk of underlying brain injury which may include brain bruising or bleeding. Most people realize that a strong blow to the head can cause the skull bones to break. Sometimes the injury results in a crack without displacement of the bone. Physicians may compare this “nondisplaced” fracture to the crack of an eggshell in which the shape of the shell remains unchanged.  These fractures usually heal on their own.  A more serious fracture, known as a depressed skull fracture, results when pieces of skull bone are displaced and press in against brain tissue. This type of skull fracture usually requires corrective surgery.


Penetrating Head Wound 

A penetrating head wound occurs when something forcefully enters the skull and penetrates the brain. Injury occurs along the path that the object travels into the brain and where it comes to rest.  The extent of brain injury depends on the object’s size and force of entry. Penetrating head wounds always damage the skull, and bone fragments in the wound may worsen the injury.  As the object travels through the brain, it disrupts blood vessels, causing bleeding. This bleeding may increase pressure inside the skull, leading to coma and, in serious cases, death. 

Intentional and accidental events cause penetrating head wounds. Examples are stab wounds, car accidents and workplace accidents (nails, screwdrivers). During natural disasters, such as hurricanes or tornadoes, flying objects can penetrate the skull. About 35% of penetrating head wounds are gunshot wounds. 

Every penetrating head wound is different, so the consequences are unpredictable. Anything can happen – from no lingering deficits after a minor injury to death from a serious injury. Deep wounds are more damaging than shallow ones.


Arterial Dissections 

Blunt or penetrating trauma to the head or neck may cause the arteries in the neck to tear. These tears are also referred to as “dissections” and are a common cause of stroke after brain injury. The carotid or vertebral arteries may be involved. Treatment may involve the use of blood thinners, placement of a stent to keep the blood vessel open or bypass surgery.


Diffuse Axonal Injury 

Nerve cells, or neurons, have long branches called axons. Axons transmit signals to other neurons throughout the brain, spinal cord, and body. Many axons running parallel make up the white matter of the brain and spinal cord — so called for the whitish color of their protective myelin sheaths. Axons are somewhat flexible but will tear when stretched suddenly by a traumatic event. This type of injury, known as shearing, damages the axons and myelin sheaths. It prevents them from working properly — disrupting communication among neurons. Without this communication, the brain cannot function properly. 

A diffuse injury is widespread or scattered — an extensive injury to axons throughout a part of the brain. Hitting your head in a car accident, fall from a bicycle, slip on icy pavement, or other accident can lead to diffuse axonal injury. Violently shaking or throwing a person can cause this type of injury. In babies, this condition is called shaken baby syndrome.  

A diffuse axonal injury can temporarily or permanently disrupt how the brain works. Since some parts of the brain are more vulnerable to injury than others, it is difficult to predict how a person will be affected. This type of injury can increase pressure inside the skull, leading to coma and sometimes death.


Cerebral Infarction/Stroke 

When a blood clot blocks the blood flow to the brain, a person has an ischemic stroke. This type of stroke is also called a cerebral infarction or brain attack. During the stroke, the brain cannot receive new supplies of oxygen and other vital nutrients from the blood. Within minutes, starving brain cells die. A stroke is a medical emergency that needs immediate treatment to prevent brain damage and death. 

Blood clots cause about 80% of all strokes. A clot, or thrombus, may form within brain or neck arteries or travel to the brain as an embolus from elsewhere in the body. 

Blood clots generally lodge in clogged arteries. Over time, bad cholesterol and other fatty substances (plaques) build up on the artery walls, narrowing the passageways. This condition is called atherosclerosis. Blood clots can get snagged on the fatty plaques or trapped in narrowed arteries. 

Blood clots from the heart or legs may get stuck in the small arteries of the brain. 

Other conditions cause blood clots. They include:

  • Heart problems, i.e., a defective heart valve or abnormal heartbeat
  • Blood disorders
  • Certain drugs, e.g., birth control pills

The effects of stroke vary. The extent of damage depends on where the clotting occurs and how long the brain survives without oxygen. 

A stroke may cause temporary or permanent injury, coma or death. After stroke, common disabilities are difficulty speaking or swallowing, paralysis on one or both sides of the body and problems with concentration, attention, learning, memory and judgment. A person may find it hard to control emotions. Their personality may change. They may feel sad or experience numbness, strange sensations or nerve pain in their hands and feet.


Anoxic/Hypoxic Encephalopathy 

The total absence of oxygen in the brain is called anoxia. Hypoxia is a shortage of oxygen. In both conditions, the brain is starved of oxygen — only to different degrees. Often these terms are confused, and used interchangeably.  Widespread brain damage that changes the way the brain works or alters its structure is known as encephalopathy. 

Anoxia quickly leads to brain injury.  Since the blood carries oxygen throughout the body, any interference in circulation means a decrease in the oxygen supply to vital organs.  Thus, when the heart stops pumping during a cardiac arrest, the oxygen supply to the brain also stops.  Unlike stroke, a heart attack cuts off oxygen to the whole brain – resulting in global injury.  Near drownings or various accidents that cause severe blood loss can result in anoxia.  

Some brain regions, such as the hippocampus and basal ganglia, are more vulnerable to damage from a lack of oxygen. They become injured faster than other parts of the brain when deprived of oxygen. 

The brainstem, which controls breathing and basic body functions, is better protected against oxygen starvation than the cerebrum. This is why a person can survive a heart attack but still suffer from physical, behavioral and mental problems. 

The most common causes of anoxia/hypoxia are:

  • Strangulation
  • Severe asthma attack
  • Blood clots in the lung
  • A crushing injury to the chest
  • Near drowning
  • Shock from massive blood loss
  • Cardiac Arrest / Irregular heartbeat (ventricular fibrillation)
  • Carbon monoxide poisoning 

After anoxic/hypoxic encephalopathy, a person may be unable to move their limbs, have slurred speech, difficulty swallowing, seizures, tremors or other movement problems. Concentration, attention, problem-solving skills, judgment and memory may be affected. Personality may change. A person may be moody and anger easily or feel sad and disinterested in life. In severe cases, a person may fall into a coma or suffer brain death. 


Increased Intracranial Pressure 

Patients’ symptoms following a brain injury are often a direct result of a build-up of pressure within the skull. The brain, its membranes, and the cerebrospinal fluid are encased within rigid skull bones; there is no leeway to accommodate the swelling or accumulation of blood (hematomas) caused by injury. Increased intracranial pressure compresses delicate brain tissue and leads to further brain injury. 

To help reduce this increased intracranial pressure, surgeons remove hematomas in the operating room or use other methods of control. They carefully monitor for signs and symptoms of increasing pressure in the brain, including: decreased alertness, drowsiness, coma, severe headache, forceful vomiting, development of weakness or paralysis of arms and/or legs, irregular breathing patterns, and changes in the pupils’ reaction to light. In addition, surgeons often insert a special device beneath the skull to monitor pressure so they can detect abnormally elevated pressures early on and respond quickly. 

Physicians may use other methods besides surgery to manage increased intracranial pressure. These include certain medications and controlled hyperventilation using a respirator to increase the breathing rate, thus reducing carbon dioxide in the blood.



Hydrocephalus may develop in individual’s following a brain injury. Hydrocephalus occurs when there is obstruction of the normal flow of cerebrospinal fluid between the fluid filled spaces of the brain. Blockage of the flow of cerebrospinal fluid will result in dilation of the brains ventricles (fluid filled spaces) which can be seen on CT or MRI Scans. Symptoms of hydrocephalus may include the deterioration of a patient’s physical, cognitive and emotional condition, as well as the failure of a patient to improve despite aggressive therapies and treatments. Most commonly, a triad of dementia, ataxia, and incontinence develops. Treatment includes the neurosurgical placement of a “shunt”. A “shunt” is a surgically placed tube connected to a brain ventricle for the purpose of diverting excessive fluid to the abdominal cavity, heart or a large vein in the neck.  (See ICP Monitor/Ventriculostomy, in the Intensive Care section later is this booklet for more information on shunts.)



A contusion is bruising of brain tissue.  It can form anywhere blood leaking from broken blood vessels pools in brain tissue, causing swelling. 

Strong, direct blows to the head cause brain contusions. They also happen when a moving head strikes an object at high speed — for example, when a head hits the windshield during a car crash. The head often suffers structural damage, such as broken skull bones (skull fracture).  Contusions can occur beneath a skull fracture or in response to an impact in which the brain shifts and rebounds against the skull.  A contusion may occur at two points: where the head hits an object (the point of impact); and where the recoiling brain strikes the opposite side of the skull. This is known as a coup-contrecoup injury.  A severe blow to one side of the head can cause even greater damage on the opposite side. 

Contusions can temporarily or permanently disrupt brain activity — depending on their size and location. Minor damage from hits or blows causes small contusions and mild symptoms. A person may blackout for only a few seconds or may not lose consciousness at all. They may feel dazed for a few days or weeks after the injury. Other symptoms are headache, dizziness, blurred vision, ringing in the ears, tiredness, sleep problems, mood changes, and having trouble remembering, concentrating, paying attention or thinking. 

Moderate and severe contusions cause longer blackouts — lasting minutes or longer. Over time, a person may develop worsening headaches, nausea and vomiting, seizures, dilation of the pupils, slurred speech, loss of coordination, inability to awaken from sleep, weakness or numbness in arms or legs, worsening confusion, restlessness and feeling upset. 

The tissue damage and bleeding associated with contusions may lead to coma and even death.  Multiple contusions may result in widespread bleeding and swelling which increases pressure on the brain. Moderate to severe contusions are life threatening and need emergency medical attention. This may include neurosurgery to open the skull to reduce pressure and/or for removal of necrotic tissue.


Hemorrhages & Hematomas 

A strong blow to the head may damage or rupture one of the blood vessels surrounding the brain, or within the brain, leading to heavy bleeding (hemorrhage) or to the slow leakage of blood from the torn vessel. Other causes of bleeding are brain lacerations (tearing of brain tissue) and penetrating wounds from bullets, knives, or other sharp instruments. The accumulation of blood from these injuries is called a hematoma.  Hematoma means “a mass of blood”.  Frequently, the neurosurgeon can remove subdural and epidural hematomas and stop the bleeding. However, a blood clot or bleeding deep within the brain tissue itself may not be treatable with surgery.


Epidural Hematoma 

In an epidural hematoma, bleeding occurs between the skull and the dura mater, the outermost membrane covering the brain. Epidural hematomas occur most frequently in conjunction with a skull fracture on the side of the head over the temporal lobe and originate from an artery. Although the underlying brain may not have been damaged initially, pressure from the hematoma can lead to brain injury.


Intracerebral/Intraparenchymal Hematoma 

Bleeding that occurs directly within brain tissue may lead to a build-up of a blood clot within the brain itself, called an intracerebral/intraparenchymal hematoma. These hematomas usually result from penetrating wounds or blood vessels that rupture.


Subdural Hematoma 

When bleeding occurs between the dura mater and the underlying membranes covering the brain itself, the term subdural hematoma is used. Subdural hematomas often occur in association with damage to the veins overlying the brain which rupture and leak into the space between the two outermost membranes (meninges) surrounding the brain. They may produce symptoms immediately or gradually as blood seeps out of torn vessels.   

The hematoma compresses the brain. Trapped blood may clot, increasing pressure on brain tissue even more. Blood leaks into tissues of the brain, causing swelling. Brain cells begin to die as they are deprived of oxygen and nutrition. As the mass of blood grows, brain damage occurs. Large, rapid bleeds may lead to loss of consciousness and death. 

There are three types of subdural hematomas:

  • Acute: After a severe brain injury; causes immediate, life-threatening symptoms
  • Subacute: After major brain injuries; symptoms appear after days but may take longer
  • Chronic: After minor brain injuries; symptoms may not be noticed for weeks 

All subdural hematomas are medical emergencies and need medical attention as soon as possible to prevent permanent brain damage and death. 

The most common cause is brain injury from a traumatic event, such as accidental blow or fall, particularly in the elderly. As the brain shrinks with age, tiny veins between the brain’s surface and dura are stretched and more easily injured.  

The effects vary, depending on which area of the brain suffers the hematoma. A person may have difficulty speaking or swallowing, memory loss, pain or numbness, paralysis on one or both sides and changes in behavior.


Subarachnoid Hemorrhage 

Uncontrolled bleeding into the space between the middle and innermost membranes (meninges) surrounding the brain is a subarachnoid hemorrhage. The middle membrane is the arachnoid mater — hence subarachnoid or “under the arachnoid”. 

Vasospasm, or constriction of the blood vessels, restricts blood flow. It is a common complication of subarachnoid hemorrhage. It can cause stroke. The blood within the arachnoid space displaces the cerebrospinal fluid (CSF) and blocks the delivery of nutrients to the brain cells. The blood can block the flow of CSF in the ventricles causing a rise in pressure, or hydrocephalus. In both stroke and hydrocephalus, brain cells starve and die. 

The most common cause of bleeding is rupture of a bulge in an artery (aneurysm). Subarachnoid hemorrhage occurs in 10–15 out of 100,000 people. It is most common in people from 20 to 60 years of age. It happens more often in women than men. 

Sometimes the cause is unknown. Bleeding may occur in abnormal knots of blood vessels (arteriovenous malformations) present on the brain’s surface at birth. A subarachnoid hemorrhage may be caused by brain injuries, bleeding disorders, and the use of blood thinners. You are more likely to have a subarachnoid hemorrhage if others in your family have suffered one. In the elderly, brain injury resulting from a fall is often responsible. Car accidents are the leading cause in young people. 

Subarachnoid hemorrhage is a medical emergency. Without treatment, the person may die. What happens after treatment depends on the location and extent of bleeding. Some people recover completely. Others are left with permanent disabilities, while some die. Common disabilities are paralysis, difficulty talking or swallowing, memory loss, pain or numbness and changes in behavior.


Intraventricular Hemorrhage 

Uncontrolled bleeding into one or more of the brain’s ventricles is called an intraventricular hemorrhage. The ventricles are spaces within the brain that make and store cerebrospinal fluid (CSF), which nourishes the brain. 

This type of hemorrhage occurs most often in premature babies. In infants born before 32 weeks of pregnancy, the veins next to the ventricles are often weak, because they are not yet fully developed. In premature babies, other complications can increase pressure in the veins, causing them to rupture and bleed easily — usually in the first few days after birth. 

The bleeding causes swelling in nearby brain tissues. Blood in the ventricles can block the flow of CSF, causing a build-up of fluid that increases pressure within the brain. This condition is called hydrocephalus or “water on the brain.” About 1 in 500 newborns develop hydrocephalus. 

In adults, intraventricular hemorrhage occurs in about 35% of people with moderate to severe brain injuries. Most often, blood leaks into the ventricles after a traumatic brain injury, such as a blow to the head during a fall or car accident. 

The swelling and rise in pressure injures brain tissues, sometimes permanently. 

How much damage occurs depends on the location and extent of bleeding. Outcomes range from little or no permanent brain damage to death. 



An aneurysm is a weak spot in a blood vessel (artery) that bulges out and fills with blood. This bulge puts pressure on surrounding tissue and nerves. It may leak or rupture, spilling blood into the brain. 

This weakness often occurs where arteries branch, but aneurysms can occur anywhere in the brain. They are common along the Circle of Willis, a ring of arteries at the base of the brain. 

The causes of aneurysm are unclear. They may occur after a brain injury or infection. With age, vessel walls weaken and aneurysms may form. You can be born with an aneurysm. They can run in families and are more common in women than men. Most aneurysms happen in people between 40 and 60 years old. 

Some aneurysms are very small and cause no problems. Aneurysms that leak or rupture can be deadly. Leaking blood damages or kills nearby brain cells and increases pressure inside the skull. A ruptured aneurysm is a life-threatening medical emergency. In 50% of cases, it leads to death. 

What happens to a person after treatment depends on how much bleeding occurs and which area of the brain suffers. A person may have difficulty speaking or swallowing, memory loss, pain or numbness, paralysis on one or both sides and changes in behavior.



Five to 10 percent of all patients with brain injury will have seizures or convulsions soon after a brain injury or even years later. Seizures indicate irritation or injury to certain areas of the brain which interferes with the normal pattern of communication and transmission of information between brain cells (neurons). During the seizures, patients often lose consciousness and their bodies shake and writhe. Since prolonged uncontrolled seizures can cause further damage to the brain, medications are often used to prevent or control them.



Brain injury can also result in coma. This condition is a state of unconsciousness in which the patient is unresponsive to and unaware of surroundings. The length of a coma varies with each brain injury and can last from a few days to several months and in rare cases years. Family members should not expect a patient to suddenly wake up from a coma as they do after a night’s sleep. Emergence from a coma is usually a very gradual process of increasing responsiveness and awareness. 

Physicians and nurses cannot predict how an individual will progress and often must be patient along with the family. 

Family members and friends often wonder if comatose patients can hear. Sometimes patients seem to show signs that they may understand when they appear to follow a simple request, like squeezing a hand. Occasionally, they seem to be calmed by a familiar voice or music. Since patients rarely remember these events later, it is impossible to know what they actually experience. Nevertheless, health care professionals recommend people approach comatose patients as if they could hear and understand.