Traumatic Brain Injury Diagnosis and Imaging

Introduction to TBI and Imaging Limitations

Noncontrast CT (NCCT) is the first-line test for acute TBI evaluation, but it has limitations in detecting certain types of brain injuries, particularly in mild TBI, according to the American College of Radiology 1
Diffuse axonal injury (DAI), a common type of TBI, is poorly visualized on CT as more than 80% of these lesions are not associated with macroscopic hemorrhage, as reported by the American College of Radiology 2

Brain MRI without contrast is recommended when initial CT is negative but unexplained neurologic findings persist, with a Class I recommendation from the American College of Radiology 3
T2* and susceptibility-weighted imaging (SWI) MRI sequences are particularly useful for detecting diffuse axonal injury in acute, early subacute, and chronic stages, with a Class IIa recommendation from the American College of Radiology 3
SWI has been reported to detect 30% more TBI-related lesions compared to conventional CT and standard MRI sequences, according to the American College of Radiology 3

Persistent neurologic symptoms following head trauma should raise suspicion for TBI even with normal initial imaging, as stated by the American College of Radiology 2
Approximately 15% of patients with mild TBI and normal CT scans will have persistent neurocognitive sequelae at 1 year, according to the American College of Radiology 2
Early MRI may have prognostic value, as studies show approximately 27% of patients with mild TBI and normal CTs show abnormalities on MRI that may predict 3-month outcomes, as reported by the American College of Radiology 2

ECG (electrocardiogram) is not used for TBI diagnosis as it evaluates heart function, not brain injury, as stated by the American College of Radiology 1, 2
Repeat assessment with CT for mild TBI with negative initial results is generally not recommended, with a Class III recommendation from the American College of Radiology 1

The American College of Radiology recommends MRI with SWI when initial CT is normal but unexplained neurologic findings persist after head trauma, as it is 3-6 times more sensitive than conventional T2* gradient echo for detecting traumatic microhemorrhages associated with diffuse axonal injury (DAI) 4, 5, 6
SWI detects hemorrhage 3-6 times more sensitively than conventional gradient echo sequences and far exceeds CT sensitivity, identifying hemorrhagic transformation in acute infarcts that would be missed on standard imaging 4
Blooming within a vessel lumen on SWI indicates intravascular thrombus, which helps localize arterial occlusion and may guide endovascular intervention decisions 7

In intracerebral hemorrhage, hematoma expansion detected on repeat imaging is associated with a nearly 5-fold increase in clinical deterioration, poor outcome, and death 8
The presence of multiple microbleeds on SWI may indicate bleeding-prone angiopathy (cerebral amyloid angiopathy, hypertensive vasculopathy), though data on whether this increases hemorrhagic transformation risk after thrombolysis remains mixed 9
Microhemorrhage burden on SWI correlates with presenting Glasgow Coma Scale scores, though the relationship between microhemorrhage number and long-term outcomes remains controversial 4, 5

Detection of chronic microbleeds helps identify patients at risk for recurrent stroke—lobar microbleeds suggest amyloid angiopathy while deep microbleeds suggest hypertensive vasculopathy 8, 9
Approximately 15% of mild TBI patients with normal CT will have persistent neurocognitive sequelae at 1 year, and early MRI with SWI showing microhemorrhages may have prognostic value for predicting these outcomes 6
No gadolinium contrast is needed for SWI in trauma or acute stroke settings 4, 6