A concussion is a mild traumatic brain injury from a direct blow to the head or sudden head movement. This injury temporarily alters normal brain function. Many mistakenly believe concussions are visible on standard medical imaging like a CT scan, leading to confusion about their role in diagnosis.
Understanding CT Scans
A Computed Tomography (CT) scan uses X-ray images from different angles to create detailed cross-sectional pictures of bones, blood vessels, and soft tissues. This technology is effective at visualizing dense structures and detecting structural abnormalities.
CT scans identify issues such as skull fractures. They can also show internal bleeding (hemorrhage) or significant swelling (edema) that might exert pressure on brain tissue. The rapid acquisition of images makes CT scans a valuable tool in emergency situations for immediate detection of structural damage.
Why Concussions Aren’t Visible on CT Scans
A concussion primarily involves a disruption of brain function rather than a visible structural alteration. When a concussive force occurs, it can stretch and damage brain cells and their connections, affecting how neurons communicate. This microscopic damage is too subtle for a standard CT scan to detect.
CT scans detect macroscopic changes, such as large bleeds, fractures, or significant swelling, which involve physical changes to the brain or skull. Since a concussion does not typically cause these visible structural changes, a CT scan of someone with a concussion usually appears normal. The functional changes associated with a concussion are not within the scope of what a CT scan can visualize.
When a CT Scan Is Used for Head Injuries
While a CT scan cannot diagnose a concussion, it plays an important role in evaluating head injuries. Medical professionals use CT scans to rule out more severe, potentially life-threatening conditions resulting from head trauma. These conditions may present with symptoms similar to a concussion but require immediate medical or surgical intervention.
A CT scan can quickly identify an intracranial hemorrhage (bleeding inside the skull), a skull fracture, significant brain swelling, or a hematoma (a collection of blood). These can be life-threatening if left untreated. A normal CT scan after a head injury is reassuring, meaning there are no immediate structural dangers, but it does not mean a concussion is absent.
How Concussions Are Diagnosed
Since CT scans do not reveal concussions, diagnosis relies on a comprehensive clinical assessment by a healthcare professional. This process begins with a detailed history of the injury, including how it occurred and any immediate symptoms observed. The individual’s medical history, including any previous concussions, is also considered.
A thorough neurological examination assesses cognitive functions like memory, concentration, and processing speed, along with balance and coordination. The healthcare provider also evaluates reported symptoms like headache, dizziness, nausea, light sensitivity, and fatigue, as their presence and severity are key indicators. Concussion diagnosis is ultimately made based on reported symptoms, injury mechanism, and findings from physical and neurological examinations.