What Exactly is a Concussion?

Courtesy of Godoy Medical Forensics


When a bump, jolt, or blow to the head causes a change in the way the brain works, it is called a concussion. A concussion is a type of traumatic brain injury (TBI) that causes the brain to move quickly back and forth inside the skull. They are sometimes considered “mild” because concussions are not typically life-threatening. Concussions are characterized by:

  • An episode of observed or self-reported transient confusion, disorientation, or impaired consciousness;
  • An episode of observed or self-reported dysfunction of memory around the time of injury;
  • Observed signs of neurological dysfunction acutely following the injury, such as:
    • Seizures;
    • Irritability, lethargy, or vomiting;
    • Headache, dizziness, fatigue;
    • Poor concentration;
  • Any period of observed or self-reported loss of consciousness lasting 30 minutes or less.

A person can suffer a concussion without having a loss of consciousness (LOC). The key point to remember is that concussions are defined by altered consciousness, the presence of which is evidence of brain injury.

How is a Concussion Diagnosed?

The initial diagnosis of concussion is based on evaluation of the symptoms a person reports, or someone else observes, after sustaining the injury. Concussion is commonly divided into three different types: Grade 1, Grade 2, and Grade 3. The chart below distinguishes the features of each:

Grade Behavior Signs Time
1 Confused but remains conscious Temporarily confused, dazed, unable to think clearly, trouble following directions  <15 minutes
2 Remains conscious but develops amnesia Similar to Grade 1 >15 minutes
3 Loss of consciousness Noticeable disruption of brain function exhibited in physical, cognitive and behavioral ways Unconscious for seconds or minutes

When a person exhibits evidence of brain dysfunction, neuropsychological assessment is used to determine the functional impact of the injury. The assessment includes a series of tests that objectively measure specific brain functions and assist clinicians in determining which area of the brain was injured and which areas are still intact. The tests evaluate attention span, orientation, memory, concentration, language, 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.

Brain imaging such as CT scans and MRIs rarely show evidence of injury due to the diffuse and subtle nature of concussions. Some of the more sophisticated and expensive imaging modalities that are available include positron emission tomography (PET), single photon emission computerized tomography (SPECT), functional magnetic resonance imaging (fMRI), and diffuse tensor imaging (DTI). These imaging studies are currently not as readily available as the CT and MRI scans.

What is Post-Concussion Syndrome?

One common consequence of concussion is the post-concussion syndrome (PCS), which is a group of symptoms that includes headache, dizziness, decreased concentration, memory problems, irritability, fatigue, visual disturbances, sensitivity to noise, judgment problems, depression, and anxiety. PCS is usually associated with mild traumatic brain injury (TBI), such as a concussion, but may also occur after moderate and severe TBI and whiplash injury. The symptoms of PCS are vague, subjective, and common in the general population. The pathophysiology is not defined, test results may or may not be abnormal, and when tests do show abnormalities, they do not follow a consistent pattern. Women and older adults appear to be more susceptible to PCS and the severity of brain injury does not appear to correlate with the risk of developing it.

How is a Concussion Managed?

Conservative management of concussions is standard practice. Physical and cognitive rest is recommended for at least 24 hours pending cessation of symptoms. Gradual return to work, school, and physical activity is also endorsed. For a person with prolonged symptoms, reevaluation and treatment may be beneficial (Evans, Concussion and mild traumatic brain injury, 2013).

Admission to the hospital is recommended if a person is at risk for immediate complications from the injury, as indicated by a decrease in cognitive function, an abnormal CT scan, a history of seizures, and a person at risk for bleeding. Admission should be considered if there is no responsible person to monitor the patient at home for signs of progression of symptoms. Observation outside of the hospital may be allowed for a person whose neurological condition is unlikely to decline.

If properly managed, the prognosis for complete recovery from a concussion is good. The time it takes to recover varies with each individual and depends on the severity of the brain damage. Recovery can occur within a few hours to several months after the injury.