Brain injury

Traumatic brain injury, or TBI, occurs when a bump or forceful blow to the head or body injures the brain and the brain no longer functions as it once did. The damage can be mild, moderate or severe.

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Symptoms of brain injury

Symptoms of a brain injury can appear as behavioral or physical changes directly following trauma to the head, or present days or weeks later. There are different symptoms for mild traumatic brain injury and moderate to severe brain injury.

Mild TBI

The signs and symptoms of mild traumatic brain injury (such as a concussion) may include:

  • Blurred vision.
  • Dilation of one or both pupils of the eyes.
  • Dizziness or loss of balance or ringing in the ears.
  • Drowsiness.
  • Headache or sensitivity to light or sound.
  • Loss of consciousness for only a few seconds or few minutes.
  • Memory problems.
  • Mood changes.
  • Nausea or vomiting.
  • Numbness/weakness in fingers and toes.
  • Sleeping more than usual.
  • Slurred speech.

Moderate to severe TBI

Moderate to severe traumatic brain injury may include the same symptoms as mild traumatic brain injury plus these additional symptoms:

  • Agitation/combativeness.
  • Coma.
  • Inability to awaken from sleep.
  • Loss of coordination.
  • Loss of consciousness for several minutes to hours.
  • Persistent headache.
  • Serious confusion.

Brain injuries in children

Infants and young children with brain injuries might not be able to clearly express the symptoms they are experiencing.

A child who has suffered a traumatic brain injury may exhibit:

  • Change in ability to pay attention.
  • Change in eating or nursing habits.
  • Change in sleeping patterns.
  • Constant crying.
  • Loss of interest in favorite activities.
  • Seizures.

Recovery from brain injuries

Severity affects recovery

Traumatic brain injuries are classified as either mild, or moderate to severe. Depending on the level of brain injury, each patient’s recovery will be different. The more moderate or severe the TBI, the more likely the patient can experience permanent brain damage.

Following a brain injury, the brain is equipped with natural repair mechanisms that can aid in recovery. When brain cells are lost after an injury, they do not come back. Instead, immune cells called inflammatory monocytes enter the injured tissue and clear away the dead brain cells. Then, another type of monocyte can work around the injury and help rebuild damaged blood vessels.

Rebuilding connections

As neurons are lost, new brain connections have to be made and are rebuilt by a process called neuroplasticity. While neuroplasticity is the reason many brain injury patients have made strong recoveries, it doesn’t happen without the patient’s help to retrain the brain with new skills.

Neuroplasticity is responsible for helping to re-route brain neurons and in finding new neural bridges to connect with to change the flow of information in the brain, as the patient re-learns skills and strengthens their thinking.

Frequently asked questions (FAQs) about brain injury

Do brain cells grow back?

When brain cells are lost due to brain injury, the brain does not make new ones. Instead, after an injury, the brain finds another way to heal the injury by creating new neural pathways, and the surviving cells adapt and take on more work.

What is an acquired brain injury?

An acquired brain injury is when the brain becomes injured from an internal or external source that is not hereditary, degenerative or congenital.

There are two types of acquired brain injury: traumatic (TBI) and non-traumatic.

  • Traumatic brain injury is a result of changed brain function after an external blow to the head.
  • Non-traumatic brain injury arises from internal factors such as infections like Meningitis, lack of oxygen, stroke or tumor.
Do TBI patients sleep a lot?

When patients have a TBI, there is a loss of neurons that assist with staying awake and regulating sleep. TBI patients often report they are experiencing different sleep patterns, excessive daytime sleepiness, increased sleep need and insomnia, especially in the first two weeks after the injury.

Patients with a severe TBI, who were in a coma, had a skull fracture or required neurosurgery, often have an exaggerated form of hypersomnia similar to those seen in patients with narcolepsy.

Depression and anxiety, post-traumatic stress disorder and chronic pain can commonly accompany patients with TBI and also exacerbate sleep issues after a traumatic brain injury.

Can someone fully recover from a traumatic brain injury?

Traumatic brain injuries (TBIs) are classified as either mild, or moderate to severe.

All TBIs can have some sort of behavioral, cognitive, emotional and or physical side effects that linger following the injury. TBI patients and caregivers should modify their expectations and timeline for recovery, depending on the severity of the injury and side effects.


Center for Disease Control and Prevention (CDC). Traumatic Brain Injury Concussion (

National Institute of Neurological Disorders and Stroke (NINDS). Traumatic Brain Injury (

MedlinePlus: National Library of Medicine. Traumatic Brain Injury (