What is mild traumatic brain injury (concussion)?

A bump, blow, jolt to the head or penetrating head injury can cause serious damage to the brain, even if no damage is visible on an MRI. These are called Traumatic Brain Injuries (TBI) by the CDC1. Mild traumatic brain injury (mTBI) is the most common form of TBI caused by the head getting struck by an object, resulting in loss of consciousness, memory deficits and disorientation2

mTBI is characterized by brief loss of consciousness and amnesia that lasts for less than an hour without structural damage that would be detectable via regular brain imaging. Whereas, TBI refers to the severe TBI that results in loss of consciousness and amnesia lasting for more than 24 hours, structural damage visible via brain imaging, and possibly coma3

mTBI can be associated with physical symptoms that cannot be attributed to other psychiatric or physical causes, such as2

  • Physical symptoms, such as lethargy, vomiting, sleep disturbances, headache, ringing in the ears, low testosterone
  • Cognitive impairments, such as disturbances in thinking, learning, amnesia, and poor judgment 
  • Changes in behavior including irritation and anger

Lasting symptoms of mTBI are often referred to as post-concussion syndrome (PCS) and impact up to 15% of individuals with a novel episode of concussions4. In some cases, these could last for weeks, months or even years5. Factors that affect the duration of mTBI recovery include gender, genetics, overall physical well-being, and any previous history of mTBI5

The problem with mTBI is that symptoms can be nonspecific and most pathologies are not visible on imaging. The diagnosis, therefore, relies on subjective reporting. In some cases, the patient may not even know that they have mTBI because the injury may have happened a long time ago. In addition, if the clinician is not familiar with mTBI, the patient may get misdiagnosed with other conditions. In these cases, treatments based on symptoms often don’t fully resolve the issue. 

Before we delve into diagnostic technologies for mTBI, it is important to understand how our nervous system works.

About the Author

Ketan Marballi is a neuroscientist who holds a Ph.D. in Cellular and Structural Biology from the University of Texas, San Antonio. Over the last decade, his research has spanned the areas of different neurodevelopmental and psychiatric disorders such as schizophrenia and alcohol abuse research. He is currently studying the molecular mechanisms of Rett syndrome, a genetic syndrome similar to autism. Ketan has guest lectured at the University of Texas at Austin, teaching epigenetics to nursing students and mentored 7 students including high school, and undergraduate and medical resident trainees for their research projects. His work has been featured in leading publications including PLoS ONE and the Journal of Molecular Medicine. He enjoys playing tennis and singing in his spare time.

References :

1. US Department of Health & Human Services. Traumatic Brain Injury | Concussion | Traumatic Brain Injury | CDC Injury Center. https://www.cdc.gov/traumaticbraininjury/index.html.

2. Kay, T; Harrington D.E.; Adams, R. et al; Definition. www.ACRM.org (1993).

3. Northeastern University. Severity of TBI. https://bouve.northeastern.edu/nutraumaticbraininjury/what-is-tbi/severity-of-tbi/.

4. Rutherford, W. H., Merrett, J. D. & McDonald, J. R. Symptoms at one year following concussion from minor head injuries. Injury 10, 225–230 (1979).

5. Prince, C. & Bruhns, M. E. Evaluation and treatment of mild traumatic brain injury: The role of neuropsychology. Brain Sciences vol. 7 (2017).

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