Concussions are a common brain injury, often resulting from a sudden jolt or blow to the head or body. A common misunderstanding is that concussions will be clearly visible on imaging tests, like a broken bone. However, standard brain scans often appear normal even when a person has sustained a concussion, which can be confusing. This article clarifies why these scans may look clear and how concussions are diagnosed.
What is a Concussion
A concussion is a mild traumatic brain injury (mTBI) caused by biomechanical forces that make the brain move rapidly within the skull. This movement temporarily disturbs how brain cells function and communicate, without causing obvious structural damage like bleeding or swelling. These functional changes lead to an energy imbalance within the brain and are responsible for the wide range of symptoms experienced after a concussion.
Standard Brain Scans and Concussions
Common brain imaging techniques, such as Computed Tomography (CT) scans and Magnetic Resonance Imaging (MRI), are designed to detect structural abnormalities within the brain. CT scans use X-rays to create cross-sectional images, identifying skull fractures, significant brain bleeds, or large areas of swelling. MRI scans use powerful magnets and radio waves, offering detailed views of soft tissues to detect smaller areas of bleeding or bruising.
These standard structural imaging tools do not show visible signs of a concussion. This is because concussions are functional injuries, disrupting the brain’s normal processes and cellular activity without causing gross structural damage that these scans can capture. Therefore, a “normal” CT or MRI scan in the context of a suspected concussion simply indicates the absence of major structural issues, not the absence of a concussion itself. Less than 10% of patients with mild traumatic brain injuries have abnormal CT or MRI results.
When Brain Scans Are Necessary
Brain scans, such as CT or MRI, are necessary in specific situations following a head injury, even if a concussion is suspected. Their primary purpose is to rule out more severe, potentially life-threatening injuries involving structural brain damage. These include intracranial hemorrhages, significant brain swelling, or skull fractures.
A doctor might order a scan if a person exhibits concerning symptoms or circumstances. These include persistent or worsening headaches, repeated vomiting, seizures, a loss of consciousness lasting more than a few minutes, or new neurological deficits like weakness, numbness, or slurred speech. Specific mechanisms of injury, such as being ejected from a vehicle, are also indicators. For children, CT scans are used more selectively due to radiation exposure, only when specific criteria are met.
How Concussions Are Diagnosed
Concussions are primarily diagnosed through a comprehensive clinical assessment. This relies on a detailed medical history of the injury and a thorough neurological examination. Healthcare professionals inquire about the injury’s mechanism and the onset and progression of symptoms. They also assess cognitive functions, including memory and concentration.
The neurological examination evaluates aspects such as vision, hearing, strength, sensation, balance, coordination, and reflexes. Common symptoms reported by individuals with concussions include headache, dizziness, confusion, memory problems, and sensitivity to light or sound. While imaging helps rule out more severe conditions, the diagnosis of a concussion is established by a healthcare professional based on these clinical findings.