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Mild Brain Injury and Concussion

What happens in a mild brain injury
Diagnosis of Mild Brain Injury
What can I do if I have a mild brain injury
Mild Brain Injury Issues
Mild Brain Injury and Concussion
Additional Resources


The term “mild brain injury” can be misleading. The term “mild” is used in reference to the severity of the initial physical trauma that caused the injury. It does not indicate the severity of the consequences of the injury.

Read Anne's story about a person who sustained a mild brain injury and the challenges she faced in understanding this injury.

The Centers for Disease Control as part of its Report to Congress on Mild Traumatic Brain Injury in the United States developed the following definition of mild brain injury:

A case of mild traumatic brain injury is an occurrence of injury to the head resulting from blunt trauma or acceleration or deceleration forces with one or more of the following conditions attributable to the head injury during the surveillance period:

  • Any period of observed or self-reported transient confusion, disorientation, or impaired consciousness;
  • Any period of observed or self-reported dysfunction of memory (amnesia) around the time of injury;
  • Observed signs of other neurological or neuropsychological dysfunction, such as—
    • Seizures acutely following head injury;
    • Among infants and very young children: irritability, lethargy, or vomiting following head injury;
    • Symptoms among older children and adults such as headache, dizziness, irritability, fatigue, or poor concentration, when identified soon after injury, can be used to support the diagnosis of mild TBI, but cannot be used to make the diagnosis in the absence of loss of consciousness or altered consciousness. Further research may provide additional guidance in this area.
  • Any period of observed or self-reported loss of consciousness lasting 30 minutes or less.

The definition focuses on the actual injury or symptoms, not the possible consequences. For many people, there are challenges in getting an accurate diagnosis and treatment, especially when there is no documented or observed loss of consciousness. There does not need to be a loss of consciousness for a brain injury to occur. 

What happens in a mild brain injury?

The brain is not a hard, fixed substance. It is soft and jello-like in consistency, composed of millions of fine nerve fibers, and "floats" in cerebral-spinal fluid within the hard, bony skull. When the head is struck suddenly, strikes a stationary object, or is shaken violently, the mechanical force of this motion is transmitted to the brain.     

When the head has a rotational movement during trauma, the brain moves, twists, and experiences forces that cause differential movement of brain matter. This sudden movement or direct force applied to the head can set the brain tissue in motion even though the brain is well protected in the skull and very resilient. This motion squeezes, stretches and sometimes tears the neural cells.  Neural cells require a precise balance and distance between cells to efficiently process and transmit messages between cells.  The stretching and squeezing of brain cells from these forces can change the precise balance, which can result in problems in how the brain processes information. Closed Head Injury 
Any time the brain suffers a violent force or movement, the soft, floating brain is slammed against the skull’s uneven and rough interior. The internal lower surface of the skull, pictured to the left, is a rough, bony structure that often damages the fragile tissues within the brain as it moves across the bone surface. The brain may even rotate during this process. This friction can also stretch and strain the brain’s threadlike nerve cells called axons.

Base of Skull

Although the stretching and swelling of the axons may seem relatively minor or microscopic, the impact on the brain’s neurological circuits can be significant.  Even a “mild” injury can result in significant physiological damage and cognitive deficits. 

A Single Neuron
Another mechanism of injury involves changes that occur in the neuron’s ability to produce energy for the cell’s vital functions in structures called mitochondria. An initial increase in energy production occurs followed by a dramatic decrease that affects the ability of the cell to produce structural proteins to preserve the diameter of the axon. This change occurs gradually after the time of impact and may be responsible for the delay in symptoms sometimes observed.

As a person recovers, the cells re-establish the precise balance needed to ensure effective information processing, but this may mean some compensation or adjustments to the neural cell’s original alignments. The more often neural cells must compensate or adjust to injury, the more likely the task takes longer and may not be as complete. For example, when a person sprains or fractures an ankle, professionals recommend cold/heat treatments, rest and supports (i.e., cast, brace) and specific exercises to help the ankle adjust to the injury and recover maximal function. Depending on the severity of the ankle injury (i.e., sprain, fracture) and what is required after recovery (i.e., long distance running, ballet), the injury to the ankle can disrupt a person’s life.

Obviously, a human brain is much more complicated than an ankle. Yet, similarly, rest, supports (i.e., compensations, modifications) and “exercises” (i.e., therapies, education) for the brain may be recommended to rehabilitate and restore useful function. Depending on the severity of the injury and what the person needs to do (i.e., care for a family, return to work or school, manage a large company), a mild brain injury can disrupt a person’s life for a short period of time or even longer.

Diagnosis of Mild Brain Injury

Due to the diffuse and subtle nature of mild brain injury, it is common for typical neuroimaging (CT scan or MRI’s) to show no evidence of injury. The damage to the brain is a real injury. The limitation of these brain imaging technologies is they often cannot detect mild brain injury. Mild brain injury can often damage the "white matter" of the brain. "White matter" consists of the axons of neurons (connections) in the brain. This is much harder to capture or visualize using common types of brain imaging.

There are newer, more sophisticated imaging technologies that show promise in more effectively capturing the damage that occurs in a mild brain injury. However these imaging technologies are currently much more expensive, and are not as readily available. Some of the newer imaging techniques include:

Positron Emission Tomography (PET)
Single Photon Emission Computerized Tomography (SPECT)
Functional Magnetic Resonance Imaging (fMRI)
Diffuse Tensor Imaging (DTI)

Neuropsychological assessment is typically used to assess the functional impact of a mild brain injury. This assessment is normally done when some type of brain dysfunction is suspected. A mild brain injury is often initially diagnosed by evaluation of the symptoms a person reports after sustaining the injury. 

The assessment is comprised of a wide range of tests that objectively measure specific brain functions. Testing includes a variety of different methods for evaluating areas like attention span, orientation, memory, concentration, language (receptive and expressive), new learning, mathematical reasoning, spatial perception, abstract and organizational thinking, problem solving, social judgment, motor abilities, sensory awareness and emotional characteristics and general psychological adjustment. The neuropsychological evaluation can be used as a starting point for a plan of rehabilitation. It can assist brain injury professionals in identifying specific cognitive areas that have been damaged, as well as those areas still intact. You can read more about neuropsychological evaluations and brain injury from the American Psychological Association.

What can I do if I have a mild brain injury?

Understanding the changes that have occurred from a brain injury is an important part of the recovery process. This makes education and awareness crucial for both the person with a brain injury as well as family and friends. The person with an injury and others need to understand that a “mild” brain injury can result in changes in thinking and memory that can affect a person’s ability to return to their life. While a person can “look fine,” brain injury is an invisible injury. 

Research has shown that education and information about the possible consequences can be helpful to the person with an injury and family members. Some basic symptoms for family and friends to be aware of include:

Early Symptoms:

  • Headache
  • Dizziness or vertigo
  • Lack of awareness of surroundings
  • Nausea with or without memory dysfunction
  • Vomiting

Later Symptoms:

  • Persistent low grade headache
  • Lightheadedness
  • Poor attention and concentration
  • Excessiveness or easy fatigue
  • Intolerance of bright light or difficulty focusing vision
  • Intolerance of loud noises
  • Ringing in the ears
  • Anxiety and depressed mood
  • Irrability and low frustration tolerance

If you suspect you have a mild brain injury, contact a brain injury professional to help with the diagnosis and treatment of a brain injury. Also contact the Brain Injury Association in your state. State Brain Injury Associations will have information to share and can connect you with support groups, programs and professionals who understand the injury.

Mild Brain Injury Issues

Some important information to share, from families and people who have sustained a mild brain injury:

The recovery from a mild injury is not always quick.
For mild brain injury, the issues are the same as moderate to severe brain injury.  While there are general guidelines for recovery, there can be wide individual variations in the timeframe for recovery. It can take several weeks, or several months for symptoms to fully resolve.

Recovery is often uneven. 
There will be “good days” and “bad days.”  This is normal in recovering from a brain injury. An important thing to keep in mind: on the “good days”, people want to get as much done as they can. Often, this can lead to overdoing it, which can bring back symptoms that were previously gone. Even on the good days, it is important to give yourself more time to complete tasks, and to listen to your body.  You cannot “tough out” a brain injury.

Create the best possible environment for recovery.  
Substances like caffeine, alcohol and nicotine can affect a person with a brain injury much more than it did before the injury. Be aware of the possible consequences of alcohol on recovery post injury.  It is recommended to abstain from alcohol consumption during the recovery period post injury. You can read more about alcohol use and recovery from a brain injury at the Ohio Valley Center for Brain Injury Prevention and Rehabilitation.

Give yourself more time to complete things. 
Issues like fatigue, attention and memory issues can cause delays in completing tasks that were easily done before the injury.  Allowing additional time to do things like laundry, menu planning, shopping, bill paying can help. Thinking out the steps needed to complete tasks and writing them down can be helpful too. Better planning can decrease stress and anxiety.

Professional help is important. 
It is important to understand the effects of a brain injury. The injury itself can impair the ability of a person to accurately assess their abilities.  And once problems are identified, often a person with a mild brain injury struggles with figuring out effective strategies to compensate for problem areas. Working with a trained brain injury professional can help identify specific problem areas, and can help implement effective strategies. You do not need to figure out brain injury all on your own.  There are useful books and resources available. 

Support groups can be helpful. 
Brain injury can be isolating.  People say things like “you look fine,” with the implication that you should be fine. It is an invisible injury. Sometimes talking with others who have experienced similar experiences can help a person with a brain injury understand they are not the only one dealing with these issues. Contact the Brain Injury Association in your state to find out about support groups or other resources that may be useful to you.

Mild Brain Injury and Concussion

It is important to understand that a concussion is a physical injury to the brain that causes a disruption of normal functioning just like any other physical injury disrupts your normal functioning. For example, some ankle injuries (i.e., sprains and fractures) are more disruptive than others, just as some brain injuries are more disruptive than others. The better we understand any injury, the better our chances are for a speedier and healthier recovery.

For the majority of people who sustain a concussion, a full recovery is possible with appropriate diagnosis and management. 

The Brain Injury Association has a Concussion Information Center, with in depth information about the management of concussion. 

Additional Resources

CDC Concussion Booklet
Road to Rehabilitation Series Part 3 - Concussion and Memory

TBI Guide, an online book about brain injury and recovery written by a neuropsychologist.

There are several books available in the Brain Injury Association Marketplace:

Brain Injury Survival Kit
In Search of Wings
Remind Me Why I'm Here
Brainlash: Maximize Your Recovery from Mild Brain Injury
Brain on a String
Shaken but not Stirred


Brain Injury Medicine: Principles and Practice, Nathan D. Zasler, MD, Editor, Douglas I Katz, MD, Editor, Ross D. Zafonte, DO, Editor, 2007, Demos Medical Publishing.
Mild Traumatic Brain Injury: A Therapy and Resource Manual Green, B,  Singular Publishing, 1997
Textbook of Traumatic Brain Injury Jonathan M. Silver (Editor), Stuart C. Yudofsky (Editor), Thomas W. McAllister (Editor), 2004 American Psychiatric Press
Horn, L.J. & Zasler, N. (1996). Medical Rehabilitation of Traumatic Brain Injury. Hanley & Belfus, Inc: Philadelphia, PA.
Kay, T. Brain Injury Association of America. Mild traumatic brain injury, 1999.

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