In an adult with suspected moderate‑to‑severe traumatic brain injury who has already had an initial non‑contrast head CT, what additional diagnostic investigations (e.g., MRI, CTA, MRA/DSA, transcranial Doppler, ICP monitoring, EEG, cervical spine imaging) should be performed?

Additional Diagnostic Investigations After Initial CT in Moderate-to-Severe TBI

In adults with suspected moderate-to-severe traumatic brain injury who have already undergone initial non-contrast head CT, you should perform CT angiography (CTA) of the brain and cervical vessels when vascular injury risk factors are present, consider MRI for unexplained neurological findings despite negative or non-diagnostic CT, obtain cervical spine imaging routinely, and implement multimodality monitoring including ICP monitoring in severe cases.

Vascular Imaging (CTA/MRA/DSA)

Perform CT angiography of supra-aortic and intracranial arteries early when specific risk factors are present. 1

Risk factors mandating vascular imaging include: 1

• Cervical spine fractures
• Focal neurological deficits unexplained by brain imaging
• Claude Bernard-Horner syndrome
• LeFort II or III facial fractures
• Basilar skull fractures
• Soft tissue neck injuries

The American College of Radiology guidelines support CTA for suspected vascular trauma as a Class IIa recommendation. 1 Even without classic risk factors, consider extending CTA indications in the most severe patients where neurological examination may be limited. 1 If CTA shows normal results but clinical suspicion for arterial dissection remains high, complete the workup with MR angiography or digital subtraction angiography. 1

Brain MRI

Obtain brain MRI without contrast when initial or follow-up CT is negative but unexplained neurological findings persist (Class I recommendation). 1

MRI provides superior detection of small TBI lesions compared to CT, with particular advantages: 1

• T2 and susceptibility-weighted imaging (SWI) sequences are Class IIa recommendations for detecting diffuse axonal injury* in acute, early subacute, and chronic stages 1
• SWI detects 30% more TBI-related lesions compared to CT and conventional MRI 1
• MRI is up to 30% more sensitive than CT for detecting acute traumatic intracranial injury 1

A critical caveat: CT scans frequently miss microhemorrhages visible only on susceptibility-weighted MRI, meaning a normal CT does not rule out these subtle injuries. 2 However, do not defer CT to await MRI in symptomatic patients—CT remains first-line for acute management to identify life-threatening lesions requiring immediate neurosurgical intervention. 2

Brain MRI with contrast can aid in visualizing subacute brain contusions (Class IIb recommendation). 1

Cervical Spine Imaging

Perform cervical spine CT routinely as part of the initial imaging strategy in severe TBI patients. 1

The French Society of Anaesthesia and Intensive Care Medicine recommends brain and cervical CT without delay in severe TBI (Grade 1+ recommendation). 1 This is particularly important given that cervical spine fractures are themselves risk factors for vascular injury requiring further investigation. 1

Intracranial Pressure (ICP) Monitoring

While the evidence provided focuses primarily on imaging rather than invasive monitoring, the guidelines emphasize that initial CT guides both neurosurgical procedures and monitoring techniques. 1 ICP monitoring becomes relevant in severe TBI management, though specific indications are beyond the scope of the imaging-focused guidelines presented.

Transcranial Doppler and EEG

The provided guidelines do not specifically address routine use of transcranial Doppler or EEG in the initial diagnostic workup of moderate-to-severe TBI. These modalities may have roles in ongoing monitoring and management but are not highlighted as primary diagnostic investigations in the acute setting.

Repeat CT Imaging

Perform repeat non-contrast head CT for neurological deterioration (Class I recommendation). 1

However, routine scheduled follow-up CT has questionable value. 1 The Brain Injury Guidelines validation study demonstrated that repeat CT and neurosurgical consultation can be safely reduced in appropriately selected patients based on clinical examination, CT findings, and risk factors. 3

Key Clinical Pitfalls to Avoid

• Do not assume a normal initial CT excludes significant injury. Up to 25% of pediatric patients with suspected brain injury show clinically relevant MRI findings not seen on CT, and this principle extends to adults with unexplained symptoms. 2
• Do not delay initial CT to obtain MRI. CT remains the reference standard for acute TBI due to availability and rapid identification of surgical lesions. 1, 2
• Do not skip vascular imaging in high-risk patients. Traumatic vascular injuries can be catastrophic if missed, and CTA is readily available during the initial CT evaluation. 1
• Maintain systolic blood pressure >110 mmHg during the diagnostic workup, as hypotension worsens neurological outcomes. 1