For a concussion, do you get a computed tomography (CT) scan with or without contrast?

CT Without Contrast is the Appropriate Imaging for Concussion

For patients with concussion, noncontrast head CT is the appropriate initial imaging modality when imaging is indicated by clinical decision rules. 1

Indications for Imaging in Concussion

Imaging is not always necessary for concussion. The decision to obtain imaging should follow established clinical decision rules:

• Mild head trauma (GCS 13-15):

  • Imaging is usually not appropriate when not indicated by clinical decision rules 1
  • Noncontrast head CT is appropriate when imaging is indicated by clinical decision rules (e.g., 2008 ACEP Clinical Policy) 1

• Moderate (GCS 9-12) or severe (GCS 3-8) head trauma:

  • Noncontrast head CT is usually appropriate for initial imaging 1

Why Noncontrast CT is Preferred

1. Rapid detection of acute pathology: Noncontrast CT can quickly identify potential complications requiring urgent intervention, such as:

   • Intracranial hemorrhage
   • Skull fractures
   • Mass effect or midline shift
   • Early signs of cerebral edema

2. Contrast is not beneficial: There is no evidence supporting the added value of contrast-enhanced CT for initial evaluation of concussion or head trauma 1, 2

3. Potential risks of contrast: Administering contrast before initial noncontrast CT can obscure subtle hemorrhages and lead to missed diagnoses 3

Follow-up Imaging Considerations

If initial noncontrast CT is unremarkable but clinical concerns persist:

• Short-term follow-up: Noncontrast head CT may be appropriate for patients with unchanged neurologic examination and unremarkable initial imaging, especially when neurologic examination is abnormal (GCS < 15) 1

• Subacute or chronic head trauma: Either noncontrast brain MRI or noncontrast head CT is appropriate for patients with unexplained cognitive or neurologic deficits 1

• Advanced imaging: MRI is more sensitive for detecting subtle traumatic brain injuries not visible on CT, particularly:

  • Small hemorrhages in the posterior fossa
  • Diffuse axonal injury
  • Subacute and chronic changes 4, 5

Common Pitfalls to Avoid

1. Administering contrast before initial evaluation: This can mask subtle hemorrhages 3

2. Relying solely on CT for subtle injuries: Small hemorrhages, especially in the posterior fossa, may be missed on noncontrast CT 3

3. Unnecessary imaging: Not all concussions require imaging; follow clinical decision rules to determine necessity 1

4. Delayed follow-up: For patients with persistent symptoms despite negative initial CT, consider MRI which is more sensitive for detecting subtle traumatic brain injuries 5

In summary, when imaging is clinically indicated for concussion, noncontrast head CT is the appropriate initial imaging modality due to its speed, sensitivity for acute hemorrhage, and ability to detect urgent surgical lesions.