What is the investigation of choice for head trauma?

Investigation of Choice for Head Trauma

Noncontrast head CT is the investigation of choice for acute head trauma, as it is the gold standard initial imaging modality that rapidly detects life-threatening intracranial hemorrhage, skull fractures, mass effect, and herniation with high sensitivity. 1, 2

Primary Imaging Modality: Noncontrast CT

The American College of Radiology provides a Class I recommendation (highest level of evidence) that noncontrast CT (NCCT) is the initial triaging diagnostic imaging test of choice for patients with acute moderate to severe traumatic brain injury. 1

Key Advantages of CT in Acute Head Trauma:

• Rapid acquisition time allows scanning to be completed in seconds, which is critical when patients are unstable or require urgent neurosurgical intervention 1, 2, 3
• High sensitivity for acute hemorrhage, including epidural, subdural, subarachnoid, and intraparenchymal hemorrhage 1, 2
• Excellent detection of skull fractures, extra-axial fluid collections, cerebral edema, mass effect, and signs of herniation 1
• Universal availability in emergency departments with minimal contraindications beyond radiation exposure 1
• No screening required for ferromagnetic substances, pacemakers, or other implanted devices, unlike MRI 1
• Compatible with monitoring equipment and ventilators that trauma patients typically require 4

Clinical Application Algorithm:

For patients with high-risk features (loss of consciousness, declining Glasgow Coma Scale score, dangerous mechanism of injury, progressive neurologic deterioration), immediate noncontrast head CT is mandatory 2

CT detects clinically important traumatic brain injury, defined as severe intracranial injury potentially resulting in death, neurologic intervention, intubation >24 hours, or admission >2 days 1

Role of MRI in Head Trauma

MRI is NOT appropriate for initial evaluation of acute head trauma, particularly when the patient has declining mental status or is unstable 1, 2

When MRI Should Be Considered (Secondary Imaging):

• Persistent unexplained neurologic deficits after a normal or non-explanatory CT scan 1, 5
• Suspected diffuse axonal injury (DAI), as >80% of DAI lesions lack macroscopic hemorrhage and are invisible on CT, requiring T2-weighted, T2*-weighted, and diffusion-weighted MRI sequences 1, 5
• Subacute or chronic head trauma (>7 days) when the focus shifts from acute hemorrhage detection to characterizing persistent symptoms 1
• Small lesions near the skull base or calvarium (small cortical contusions, subdural hematomas) that CT may miss 1, 5
• Long-term prognostication in mild TBI patients with normal CT, as approximately 27% will show abnormalities on MRI that may predict 3-month outcomes 1, 5

Critical Limitation of MRI:

A prospective multicenter study found that while MRI detected additional lesions in 27-33% of cases with normal CT, these findings did not affect acute management decisions, making MRI inappropriate for initial triage 1, 5

Common Pitfalls to Avoid:

• Never delay CT imaging for "medical stabilization" in acute trauma with high-risk features, as this worsens outcomes 2
• Never order MRI first in acute head trauma with declining mental status, as the longer scanning time wastes critical time when neurosurgical intervention may be needed 1, 2
• Do not attribute declining consciousness to other causes (drugs, metabolic disorders) when clear trauma history with high-risk features exists 2
• Avoid routine repeat CT in patients with negative initial CT and no neurologic deterioration, as delayed intracranial hemorrhage occurs in <0.5% of cases 1
• Do not use skull radiographs, as they provide no useful information compared to CT and are not recommended 1

Severity-Based Approach:

Moderate to severe TBI (GCS 3-12): Noncontrast head CT is mandatory and should be performed immediately 1, 2

Mild TBI (GCS 13-15) with high-risk features: Noncontrast head CT is indicated 1, 2

Mild TBI with normal CT but persistent symptoms at follow-up: Consider MRI for prognostication, as 15% will have neurocognitive sequelae at 1 year 1, 5

Special Populations:

Anticoagulated patients with positive initial CT warrant routine follow-up CT, as they have a 3-fold increased risk of bleeding progression (26% vs 9%) 1

Pediatric patients follow the same algorithm, with noncontrast head CT as the investigation of choice for acute trauma 1