A concussion is a type of TBI (traumatic brain injury). They can be referred to as a “mild TBI” because they are not usually life-threatening. Concussions occur when a hard hit to the head or body causes the brain to move in the skull. The movement of the brain in the skull can cause injury to nerve cells within the brain. This type of injury does not usually cause skull fracture, bleeding in the brain, or swelling of the brain. Because concussions are an injury to the brain cells, they are a microscopic cellular injury. A microscopic injury is not visible on many imaging tests which is why x-rays, CT scans, and MRI’s are usually normal despite the child or teen suffering a concussion.
X-Ray: X-rays are designed to look at bone and could help show a skull fracture, which is rarely present in a typical concussion.
CT Scan: A CT scan is also called a CAT scan which stands for computed tomography. It can detect bleeding or swelling in the brain as well as skull fractures. It uses a combination of x-rays and a computer to generate images of the brain structures. CT scans do expose patients to radiation. A CT scan may be indicated when it is likely a concussion requires immediate surgical intervention (surgery). Some indications for this may be if there is sign of a skull fracture, multiple episodes of vomiting, memory loss more than 30 minutes before the injury, seizure after injury, or a dangerous mechanism of injury (such as being ejected from a vehicle or a pedestrian getting hit by a car).
MRI Scan: An MRI scan stands for magnetic resonance imaging. This type of test uses magnets, radio waves, and a computer to generate images of the brain structures. It can detect bleeding or swelling in the brain as well as skull fractures. Unlike a CT scans, MRI scans do NOT expose patients to radiation. When brain imaging is recommended, an MRI is typically not the first choice. In cases when a CT scan is indicated, an MRI may eventually be indicated as well. In these cases, an MRI may be considered when symptoms persist and are progressive, and patients are not recovering as expected.
Though imaging studies (X-ray, CT, MRI) can be useful for certain individuals with “mild TBI” (concussion), most often these studies are not indicated. Avoiding these tests when not necessary helps avoid patient exposure to radiation and out of pocket costs for families. Concussion can be diagnosed without these studies though a detailed history of symptoms post injury. In addition to the patient history, we evaluate concussions though a comprehensive neurologic exam (including balance and vestibular and visual system assessment) as well as cognitive testing.
References: www.cdc.gov, Giza, C. C. and Hovda, D.A., The Neurometabolic Cascade of Concussion. Journal of Athletic Training. 2001; 36(3): 228–235.
www.UpToDate.com, Evans, R.W and Whitlow, C.T., Acute mild traumatic brain injury (concussion) in adults. 3/5/2018.