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Traumatic Brain Injury

By: Carine Human

Picture of the brain

The brain is composed of three parts: the brainstem, cerebellum, and cerebrum. The cerebrum is divided into four lobes: frontal, parietal, temporal, and occipital. While an injury may occur in a specific area, it is important to understand that the brain functions by inter-relating its component parts.

Every patient is unique and some injuries can involve more than one area or a partial section, making it difficult to predict which specific symptoms the patient will experience.

What is a traumatic brain injury?

Traumatic brain injury (TBI) is an injury to the brain caused by a blow or jolt to the head from blunt or penetrating trauma. Common causes include car or motorcycle crashes, falls, sports injuries, and assaults. The injury that occurs at the moment of impact is known as the primary injury and it can involve a specific lobe of the brain or can involve the entire brain. Skull fractures sometimes happen, but not always. At the time of impact, the brain are jolted around inside the skull and the crashing against the skull causes bruising, bleeding, and tearing of nerve fibers (Fig. 1). At that point in time the person may be confused, not remembering what happened, have blurry vision and dizziness, or lose consciousness. At first the person may appear fine, but their condition can decline rapidly. After the initial impact occurs, the brain undergoes a delayed trauma which means it swells and pushes against the skull resulting in reduced flow of oxygen-rich blood. This is called secondary injury, which is often more damaging than the primary injury.

Injuries of this nature are classified according to the severity and mechanism of the injury:

  • A mild injury means the person is awake with his eyes open. Symptoms can include confusion, disorientation, memory loss, headache, and brief loss of consciousness.
  • With a moderate injury the person is lethargic and his will eyes open to stimulation. Loss of consciousness lasting 20 minutes to 6 hours. Some brain swelling or bleeding causing sleepiness, but can still be woken up.
  • In severe injury the person is unconscious and his eyes will not open, even with stimulation.

Picture of brain trauma

Types of brain injuries.

Various types of traumatic brain injuries occur. They are divided in two groups namely:

Diffused injuries, which involves the entire brain and include:

  • Concussion, which is a mild head injury that can cause a brief loss of consciousness and usually does not cause permanent brain injury.
  • Diffuse axonal injury (DAI). This is the shearing and stretching of the nerve cells at the cellular level. This is usually the result when the brain quickly moves back and forth inside the skull, tearing and damaging the nerve axons. Axons connect one nerve cell to another throughout the brain, like telephone wires.
  • Traumatic Subarachnoid Hemorrhage (tSAH) is bleeding into the space that surrounds the brain. This space is normally filled with cerebrospinal fluid (CSF), which acts as a floating cushion to protect the brain. Traumatic SAH occurs when small arteries tear during the initial injury. The blood spreads over the surface of the brain causing widespread effects.

Focal injuries, which involves specific areas of the brain including:

  • Contusion, which is a bruise to a specific area of the brain caused by an impact to the head. This is divided in two groups i.e. coup injuries when the brain is injured directly under the area of impact and contre-coup injuries when the brain it is injured on the side opposite the impact.
  • Hematoma is a blood clot that forms when a blood vessel ruptures. A hematoma may be small or it may grow large and compress the brain. Symptoms vary depending on the location of the clot. Over time the body reabsorbs the clot. Sometimes surgery is performed to remove large clots.

A person who has suffered a TBI is more likely to have a combination of injuries, each of which may have a different level of severity. This makes it difficult to establish the exact location of an injury, as more than one area is usually involved.

A further complication may arise as a result of the body's inflammatory response to the primary injury and is called secondary brain injury. Extra fluid and nutrients accumulate in an attempt to heal the injury. In other areas of the body, this is a good and expected result that helps the body heal. However, brain inflammation can be dangerous because the rigid skull limits the space available for the extra fluid and nutrients. Brain swelling increases pressure within the head, which causes injury to parts of the brain that were not initially injured. The swelling happens gradually and can occur up to 5 days after the injury.

What are the symptoms?

Depending on the type and location of the injury, the person's symptoms may include:

Loss of consciousness

  • Confusion and disorientation
  • Memory loss / amnesia
  • Fatigue
  • Headaches
  • Visual problems
  • Poor attention / concentration
  • Sleep disturbances
  • Dizziness / loss of balance
  • Irritability / emotional disturbances
  • Feelings of depression
  • Seizures
  • Vomiting