CT Imaging for Traumatic Brain Injury: Contrast is NOT Used
For traumatic brain injury, CT scans must be performed WITHOUT contrast. Noncontrast CT (NCCT) is the definitive initial imaging modality for all severities of acute TBI, and contrast administration may obscure critical hemorrhagic findings. 1, 2
Why Noncontrast CT is Mandatory
- Contrast obscures hemorrhage detection: Intravenous contrast can mask early complications such as intracranial bleeding, which is the primary pathology requiring immediate identification in TBI. 2
- NCCT is highly sensitive for critical findings: Noncontrast CT reliably detects intracranial hemorrhage (with contrast differences of 30-50 HU), extra-axial fluid collections, skull fractures, cerebral edema, mass effect, and signs of herniation—all the clinically actionable findings in acute TBI. 1, 3
- Speed and availability: NCCT provides rapid acquisition time with widespread availability, making it ideal for emergency triage decisions regarding surgery, admission, or discharge. 1
When Contrast IS Appropriate in Head Trauma
Contrast-enhanced studies are only indicated when vascular injury is specifically suspected, but this requires specialized protocols, not routine contrast CT: 1, 2
- CT angiography (CTA) of head and neck: Use when intracranial arterial injury is suspected based on clinical risk factors (e.g., skull base fractures, penetrating injury, cervical spine fracture) or positive findings on initial NCCT. 1
- CT venography (CTV) of head: Use when intracranial venous injury is suspected (e.g., fractures crossing venous sinuses). 1
These are separate, targeted studies—not routine contrast-enhanced CT—and are performed in addition to, not instead of, the initial noncontrast CT. 1, 2
Clinical Application by TBI Severity
Mild TBI (GCS 13-15): NCCT is indicated only when clinical decision rules (Canadian CT Head Rule, New Orleans Criteria, or NEXUS-II) identify risk factors such as age >60 years, vomiting, post-traumatic amnesia, loss of consciousness, coagulopathy, or dangerous mechanism of injury. 1, 4
Moderate TBI (GCS 9-12) or Severe TBI (GCS 3-8): NCCT is always the appropriate initial imaging study—no exceptions. 1, 4
Penetrating trauma: NCCT is the initial study of choice. 1
Critical Pitfall to Avoid
Never order CT with intravenous contrast for routine head trauma evaluation. This is a common error that provides no additional diagnostic value and may actually obscure hemorrhage, potentially delaying critical neurosurgical intervention. 2 If you suspect vascular injury, order the appropriate study (CTA or CTV), not a standard contrast-enhanced CT. 1, 2
Role of MRI
MRI is not indicated as a primary evaluation tool for acute TBI, though it is more sensitive for detecting diffuse axonal injury and subtle parenchymal changes. 1, 5 MRI may be appropriate for subacute or chronic TBI with persistent unexplained neurologic or cognitive deficits when NCCT findings are normal. 1, 4