When should a plain cranial CT (Computed Tomography) scan be ordered for a patient with a head injury?

When to Order Plain Cranial CT Scan in Head Injury

Order a non-contrast head CT scan for any head injury patient with GCS <15 at 2 hours post-injury, loss of consciousness, amnesia, vomiting ≥2 episodes, age ≥65 years, signs of skull fracture, focal neurological deficits, posttraumatic seizure, or anticoagulation therapy. 1, 2

High-Risk Criteria Requiring Immediate CT (Sensitivity 100% for Neurosurgical Intervention)

These factors mandate CT scanning based on validated clinical decision rules:

• GCS score <15 at 2 hours after injury - This is the single most important predictor and appears in all major guidelines 3, 1, 4
• Suspected open or depressed skull fracture 1
• Signs of basilar skull fracture (hemotympanum, raccoon eyes, Battle's sign, CSF otorrhea/rhinorrhea) 3, 1
• Vomiting ≥2 episodes - Significantly increases risk of intracranial injury 3, 1, 5
• Age ≥65 years - Independently increases risk even with normal examination 3, 1, 5

Medium-Risk Criteria Requiring CT (Sensitivity 98.4% for Clinically Important Brain Injury)

• Amnesia >30 minutes before impact 3, 4
• Dangerous mechanism of injury (pedestrian struck, ejection from vehicle, fall >3 feet or 5 stairs) 3, 4
• Severe headache 1, 5
• Focal neurological deficits (any abnormal finding suggesting intracranial injury) 1, 2, 5
• Posttraumatic seizure 1, 5

Anticoagulation: A Critical Special Case

All anticoagulated patients with head trauma require CT scanning regardless of symptoms or GCS score. 6 This is a Level A recommendation from ACEP. 6

• Anticoagulated patients have 3.9% incidence of intracranial hemorrhage versus 1.5% in non-anticoagulated patients 6
• This applies to warfarin, heparin, and direct oral anticoagulants (DOACs) 6
• Even patients with GCS 15 and normal neurological examination require imaging if anticoagulated 6, 7
• The threshold for imaging must be "very low" due to consequences of missing early hemorrhage 6

When CT Can Be Safely Avoided

CT can be safely omitted only when ALL of the following are present: 1, 2

• GCS score of 15 maintained throughout evaluation
• No loss of consciousness
• No amnesia (retrograde or anterograde)
• No headache
• No vomiting
• No physical evidence of trauma above the clavicles
• No focal neurological deficits
• Age <60-65 years
• No anticoagulation or antiplatelet therapy
• No bleeding disorders
• No previous neurosurgical procedures

Common Pitfalls to Avoid

Loss of consciousness is NOT required for significant intracranial injury. A critical study found that 16% of pediatric patients with GCS 15 and NO loss of consciousness had intracranial injury, with 3 requiring surgery. 8 Similarly, in adults, 17.2% of mild head injury patients with normal or near-normal examinations harbored intracranial lesions on CT, with 58 requiring surgery. 9

Skull fracture absence does NOT exclude intracranial injury. While skull fracture increases risk 20-fold for neurosurgical intervention, 45% of patients with intracranial injury had no fractures. 8, 5 Conversely, skull fracture has poor negative predictive value. 8

Normal initial examination does NOT guarantee safety. Studies demonstrate that 6.7-17% of patients with GCS 15 and seemingly minor injuries have abnormal CT findings. 9, 5 Clinical observation alone without CT is inadequate. 9

Algorithm for Decision-Making

1. First, assess for high-risk criteria (GCS <15 at 2h, skull fracture signs, vomiting ≥2, age ≥65) → If ANY present: Order CT immediately 3, 1

2. Second, check anticoagulation status → If on warfarin, heparin, DOACs, or antiplatelet agents: Order CT immediately 6

3. Third, evaluate medium-risk criteria (amnesia >30min, dangerous mechanism, severe headache, focal deficits, seizure) → If ANY present: Order CT 3, 4

4. Only if ALL high and medium-risk criteria are absent AND patient is not anticoagulated: Consider observation without CT 1, 2

Post-CT Management

If CT is negative and patient has GCS 15: Safe discharge is supported with proper instructions. 2 No patient with mild TBI and negative initial CT required neurosurgical intervention in multiple large prospective studies. 2

If CT shows any abnormality: Admission and neurosurgical consultation are warranted, with repeat CT indicated for neurological deterioration or moderate-to-severe TBI. 3