CT Scan Decision for Minor Head Injury Without Loss of Consciousness
Based on the Canadian CT Head Rule, this patient does NOT require a CT scan if they have no high-risk or medium-risk criteria beyond the isolated forehead swelling. 1, 2
Applying the Canadian CT Head Rule
The Canadian CT Head Rule requires CT scanning only when specific risk factors are present. Your patient must be evaluated for the following criteria:
High-Risk Criteria (100% sensitive for neurosurgical intervention) 1, 2
Does the patient have ANY of these?
- GCS score <15 at 2 hours post-injury 1, 2
- Suspected open or depressed skull fracture 1, 2
- Signs of basilar skull fracture (hemotympanum, raccoon eyes, Battle's sign, CSF otorrhea/rhinorrhea) 1, 2
- Vomiting ≥2 episodes 1, 2
- Age ≥65 years 1, 2
Medium-Risk Criteria (98.4% sensitive for clinically important brain injury) 1, 2
Does the patient have ANY of these?
- Amnesia before impact >30 minutes 1, 2
- Dangerous mechanism of injury (pedestrian struck by vehicle, ejection from vehicle, fall from height >3 feet or 5 stairs) 1, 2
Critical Assessment Points for Your Patient
You stated: Small forehead swelling, no loss of consciousness, no dizziness
You must clarify:
- Current GCS score - If GCS is 15 and maintained throughout evaluation, this is reassuring 1, 3
- Vomiting episodes - Has the patient vomited at all? Two or more episodes mandate CT 1, 2
- Patient age - Is the patient ≥65 years old? This alone requires CT 1, 2
- Mechanism of injury - "Banged head on door" suggests low-energy mechanism, but confirm it wasn't a fall from height or high-velocity impact 1, 2
- Amnesia duration - Any memory gap before the injury? If >30 minutes, CT is indicated 1, 2
- Anticoagulant use - Is the patient on warfarin, NOACs, or antiplatelet agents? This mandates CT regardless of other criteria 4, 1
Evidence Supporting This Approach
The absence of loss of consciousness does NOT exclude significant injury. Studies demonstrate that 4.9% of patients without loss of consciousness or amnesia develop intracranial lesions, and 0.5% require neurosurgery 5, 4. However, the Canadian CT Head Rule maintains 100% sensitivity for detecting injuries requiring neurosurgical intervention when applied to patients without loss of consciousness 3.
A prospective study of 240 patients with minimal head injury (no loss of consciousness) found that the Canadian CT Head Rule was 100% sensitive for intracranial hemorrhage, and all positive cases had either high-risk or medium-risk criteria present 3. Importantly, none of these patients required ICU admission or surgical intervention 3.
Clinical Decision Algorithm
IF the patient has:
- GCS 15 maintained throughout evaluation
- No vomiting
- Age <65 years
- No anticoagulant use
- No dangerous mechanism
- No amnesia >30 minutes
- No signs of skull fracture
THEN: CT scan is NOT indicated 1, 3
IF ANY of the above criteria are present: Obtain non-contrast head CT immediately 1, 2
Special Populations Requiring Enhanced Vigilance
Anticoagulated patients: Proceed directly to CT regardless of other criteria, as they have 3.9% risk of intracranial hemorrhage versus 1.5% in non-anticoagulated patients 1. Consider 24-hour observation with repeat CT even if initial scan is negative 4.
Elderly patients (≥65 years): Age alone is a high-risk criterion requiring CT, as elderly patients have significantly higher rates of intracranial injury 1, 2.
Common Pitfalls to Avoid
- Do not assume isolated scalp swelling is benign - Evaluate for underlying skull fracture by palpation and assess for depression 1, 2
- Do not discharge without clear return precautions - Even with negative evaluation, instruct patient to return immediately for worsening headache, vomiting, confusion, or neurological symptoms 4, 6
- Do not rely solely on patient reassurance as indication for CT - Studies show 24.2% of CTs in minimal head injury are ordered for patient reassurance, contributing to unnecessary imaging 3
- Do not forget to ask about anticoagulants - This is the most commonly missed high-risk factor 4, 1