What are the diagnostic requirements for cerebral contusion in a patient with symptoms like headache, confusion, and seizures, considering age and medical history?

Diagnostic Requirements to Rule In Cerebral Contusion

Cerebral contusion is definitively diagnosed by non-contrast head CT imaging, which remains the gold standard for acute head trauma evaluation, though MRI is more sensitive for detecting contusions during subacute and chronic stages. 1

Imaging Modalities for Diagnosis

CT Scanning (Primary Modality)

• Non-contrast head CT is the definitive imaging modality for diagnosing cerebral contusion in the acute setting, detecting 56% of brain contusions with particular effectiveness for hemorrhagic components (77% detection rate). 1
• CT should be obtained immediately when any of the following clinical indicators are present, as these predict intracranial injury requiring intervention. 2, 3

MRI (Superior Sensitivity)

• MRI detects 98% of brain contusions compared to CT's 56%, making it the superior modality for documenting contusions during subacute and chronic stages of head injury. 1
• MRI appearance varies based on T1/T2-weighting and contusion constituents (edema, hemorrhage, encephalomalacia), with hemorrhagic components appearing as high signal on T1-weighted images. 1

Clinical Indicators Requiring CT Imaging

High-Risk Features (Canadian CT Head Rule)

The following factors mandate immediate CT scanning with strong evidence: 2, 3

• GCS score less than 15 at 2 hours post-injury (LR 4.9; specificity 97%) 2, 4
• Age greater than 60-65 years (validated across multiple decision rules) 2, 3, 4
• Suspected open or basilar skull fracture (LR 16; specificity 99%) 2, 4
• Vomiting more than once (LR 3.6; specificity 92%) - particularly concerning if ≥2 episodes 2, 4
• Any decline in GCS score (LR range 3.4-16; specificity 91-99%) 4

Additional Risk Factors (New Orleans Criteria)

• Headache (any head pain) 2, 3
• Seizure activity - patients with seizure-related falls have 90.9% incidence of intracranial hematomas versus 39.8% in other fall mechanisms 5
• Deficit in short-term memory (persistent anterograde amnesia) 2
• Physical evidence of trauma above the clavicle 2, 4
• Drug or alcohol intoxication 2, 4

Mechanism-Based Indicators

• Pedestrian struck by motor vehicle (LR range 3.0-4.3; specificity 96-97%) 4
• Fall from height >1 meter 4
• Ejection from vehicle 4

Prognostic Factors After Diagnosis

Once cerebral contusion is identified on imaging, the following features predict poor outcomes: 6

• Baseline GCS score - lower scores indicate worse prognosis 6
• Basal cistern status and midline shift (MLS) - compression or obliteration indicates mass effect 6
• Intracranial pressure (ICP) elevation 6
• CT grade of cerebral edema - higher grades correlate with worse outcomes 6
• Volume of contusion - larger contusions have worse prognosis 6
• CSF-glucose/lactate ratio - abnormal ratios predict poor outcomes 6

Critical Pitfalls to Avoid

Do Not Dismiss Isolated Symptoms

• Never attribute confusion or decreased consciousness solely to seizure activity without excluding mass lesion by CT, as 90.9% of seizure-related head injuries have intracranial hematomas. 5
• Do not dismiss isolated vomiting as benign - it is a validated predictor across all major clinical decision rules for clinically important brain injury. 2, 7

Special Populations Requiring Lower Threshold

• Patients on anticoagulation or antiplatelet therapy have 3.9% versus 1.5% risk of intracranial hemorrhage and require CT even with minimal symptoms. 3
• Elderly patients (>60 years) have significantly higher risk based on age alone. 2, 3
• Patients with bleeding disorders or previous neurosurgical procedures require individualized assessment with lower threshold for imaging. 3

Timing Considerations

• Failure to reach GCS 15 within 2 hours of injury is an absolute indication for CT scanning. 2
• Any neurological deterioration, even from GCS 15 to 14, dramatically increases risk and mandates immediate imaging. 8, 4

Definitive Diagnostic Criteria

The diagnosis of cerebral contusion is confirmed when CT or MRI demonstrates parenchymal brain injury with or without hemorrhagic components in the appropriate clinical context. 1 Clinically unimportant lesions are defined as solitary contusions less than 5mm in diameter, but any larger lesion or those with mass effect require neurosurgical consultation. 2