Can I sustain a traumatic brain injury that does not appear on a head computed tomography scan?

Can You Have a TBI That Doesn't Show on Head CT?

Yes, you can absolutely sustain a traumatic brain injury that does not appear on a head CT scan. CT scans miss many types of brain injuries, particularly diffuse axonal injury and subtle parenchymal damage, even in patients with severe symptoms.

Why CT Scans Miss Brain Injuries

CT scanning has significant limitations in detecting traumatic brain injury, particularly for certain injury patterns:

• MRI is more sensitive than CT for detecting all posttraumatic lesions except skull fractures and subarachnoid hemorrhage 1
• CT fails to visualize many parenchymal injuries, diffuse axonal injury, and subtle brain changes that MRI readily detects 1, 2
• In one study, 60% of TBI patients had injuries visible on MRI that were completely missed by CT scan, most commonly corpus callosum shear injuries 3
• Advanced imaging reveals that standard CT has "poor visualization of underlying posttraumatic changes to brain parenchyma" 4

Clinical Evidence of TBI Despite Normal CT

Severe neurological impairment can occur with completely normal CT scans:

• In a series of severe head injuries, 10.2% of patients with Glasgow Coma Scale scores indicating severe TBI had completely normal CT scans throughout the acute period (1-7 days post-injury) 5
• Among these patients with normal CTs but severe symptoms, 19.5% remained comatose for weeks and developed severe permanent disability 5
• One-fifth of severely head-injured patients with normal CT scans developed serious permanent disability, demonstrating that absence of CT findings does not equal absence of significant brain injury 5

Types of Injuries CT Commonly Misses

Specific injury patterns that CT fails to detect include:

• Diffuse axonal injury (DAI): The most commonly missed injury pattern, particularly affecting the corpus callosum and deep white matter 2, 4, 3
• Subtle contusions and parenchymal injuries that don't cause significant hemorrhage 1, 2
• Early ischemic changes and perfusion abnormalities 4
• Microhemorrhages that require susceptibility-weighted imaging to visualize 6

When to Consider MRI Despite Normal CT

MRI should be obtained when clinical findings don't match CT results:

• If the CT does not demonstrate pathology adequate to account for the clinical state, MRI is warranted 1
• MRI provides additional diagnostic information beyond CT in approximately 25% of pediatric patients with suspected brain injury 6
• Diffusion-weighted imaging (DWI) is most sensitive in the acute phase (first few days) when cytotoxic edema causes restricted water diffusion 6

Critical Clinical Implications

The absence of CT findings should never provide false reassurance:

• Patients with mild TBI (GCS 14-15) can be safely discharged after 6 hours if they have normal clinical examination AND normal CT, but they remain at risk for developing cognitive, psychosocial, and neurobehavioral abnormalities even with normal imaging 7
• Up to 1.5% of patients with GCS 15 may deteriorate, with 57% of deteriorations occurring within the first 24 hours, regardless of initial CT findings 7
• The final outcome in severe TBI with normal CT is more closely related to duration of coma than to imaging findings 5

Common Pitfalls to Avoid

Do not assume normal CT equals no brain injury:

• A normal CT does not completely exclude traumatic brain injury, particularly mild or diffuse injuries 6, 1
• All injuries requiring immediate therapeutic intervention or change in management were identified by CT scan 3, but this doesn't mean CT detects all clinically significant injuries
• Discharge instructions are poorly remembered by 23% of mild TBI patients, so written instructions and responsible third-party monitoring are essential even with normal CT 7

When CT Is Sufficient

CT remains the appropriate initial imaging modality because:

• It rapidly identifies life-threatening injuries requiring immediate neurosurgical intervention 8, 2
• It's fast, widely available, and compatible with monitoring equipment 1
• Less than 1% of mild TBI patients with GCS 15 will have lesions requiring neurosurgical intervention 8, 9

The key message: A normal head CT does not rule out traumatic brain injury. Clinical correlation is essential, and MRI should be considered when symptoms persist or worsen despite normal CT findings.