Does a Concussion Show Up on a CT Scan?
No, a concussion (mild traumatic brain injury) typically does NOT show up on a CT scan—conventional neuroimaging is usually normal in concussive injury. 1
Understanding Why CT is Usually Normal in Concussion
CT scans detect structural abnormalities like skull fractures, intracranial hemorrhage (subdural, epidural, intracerebral, or subarachnoid), and brain contusions, but concussion is primarily a functional brain injury without visible structural damage on conventional imaging. 1
The American Academy of Pediatrics explicitly states that routine CT or MRI imaging contributes little to concussion evaluation and management because the imaging is typically normal. 1
Only 10% of diffuse axonal injury (DAI) associated with more severe traumatic brain injury is positive on CT, because over 80% of these lesions lack macroscopic hemorrhage. 1
When CT Scanning IS Indicated Despite Normal Expected Results
While CT won't show the concussion itself, it serves a critical role in ruling out more serious structural injuries that can occur with the same mechanism:
CT is the test of choice during the first 24-48 hours after head injury to evaluate for intracranial hemorrhage, skull fractures, and other structural abnormalities requiring neurosurgical intervention. 1
High-risk features warranting CT include Glasgow Coma Scale score less than 15 at 2 hours post-injury, suspected skull fracture, worsening headache, and irritability on examination. 1
The purpose of CT in suspected concussion is not to visualize the concussion itself, but to exclude life-threatening complications like intracranial bleeding that may require immediate intervention. 1
The Role of MRI in Concussion
MRI is more sensitive than CT for detecting subtle traumatic lesions including small cortical contusions, subdural hematomas near the skull base, and white matter injuries in diffuse axonal injury. 1
Approximately 27% of mild TBI patients with normal CT show abnormalities on early MRI (such as small cortical contusions or hemorrhagic axonal injury), which may help predict 3-month outcomes. 1
However, MRI findings rarely change acute management in the concussion setting, though they may provide prognostic value for patients with persistent unexplained neurologic deficits after normal CT. 1
MRI is not recommended for initial evaluation of acute concussion but may be considered when initial CT is normal and neurologic findings persist unexplained. 1
Common Clinical Pitfalls
Do not assume absence of serious injury based on normal CT alone—clinical assessment remains paramount, as concussion is a clinical diagnosis based on symptoms and examination findings, not imaging. 1
Avoid using terms like "ding" or "getting your bell rung" in a way that minimizes injury severity, though athletes may be more forthcoming about symptoms when these colloquial terms are used during history-taking. 1
A normal SAC (Standardized Assessment of Concussion) score does not exclude intracranial injury—38.2% of patients with CT-positive brain injuries had normal SAC scores (≥25) in one study. 2
Do not order routine CT for every suspected concussion—imaging decisions should be guided by clinical decision rules and risk stratification, as most concussions will have normal imaging and unnecessary CT exposes patients to radiation. 1