What is the management approach for a patient with suspected diffuse axonal injury?

Management of Diffuse Axonal Injury

For patients with suspected diffuse axonal injury, immediately obtain non-contrast CT as first-line imaging, maintain systolic blood pressure >110 mmHg, control ventilation to prevent hypocapnia, and obtain MRI with specialized sequences (T2-weighted GRE, susceptibility-weighted imaging, and diffusion-weighted imaging) when CT is normal but neurologic findings persist.* 1, 2, 3

Immediate Diagnostic Imaging

Non-contrast CT is mandatory as the first-line imaging modality and should be performed immediately upon presentation in all patients with suspected moderate to severe traumatic brain injury 1, 2, 3. However, CT has significant limitations—it detects only 10% of DAI cases because most lesions lack macroscopic hemorrhage visible on conventional CT 2, 3.

MRI is indicated when CT results are normal but persistent unexplained neurologic findings are present (Class I recommendation from the American College of Radiology) 1, 2, 3. The optimal MRI sequences for DAI detection include:

• T2-weighted gradient-echo (GRE) imaging* for detecting microhemorrhages 1, 2, 3
• Susceptibility-weighted imaging (SWI), which is 3-6 times more sensitive than T2* GRE in detecting hemorrhagic axonal injuries 2, 3
• Diffusion-weighted imaging (DWI) to visualize axonal injuries not easily appreciated on other sequences 1, 2, 3

MRI can detect DAI lesions within the first 24 hours after injury, with approximately 27% of mild TBI patients with normal CT showing abnormalities on early MRI that improve prediction of 3-month outcomes 2, 3.

Acute Physiological Management

Management focuses on preventing secondary brain injury, as there is no specific treatment for the primary axonal damage itself 1, 2.

Blood Pressure Management

Maintain systolic blood pressure >110 mmHg to ensure adequate cerebral perfusion 1, 2. Avoid hypotension, which compounds secondary brain injury 2.

Ventilation Control

Control ventilation through tracheal intubation and mechanical ventilation with end-tidal CO2 monitoring 1, 2. Prevent hypocapnia, which causes cerebral vasoconstriction and increases the risk of brain ischemia 1, 2.

Intracranial Pressure Management

• ICP monitoring is recommended for patients with severe TBI to detect intracranial hypertension, with intervention threshold typically at ICP >20 mmHg 2
• External ventricular drainage is suggested for treating persisting intracranial hypertension despite sedation and correction of secondary brain insults 2
• Decompressive craniectomy may be considered for refractory intracranial hypertension in multidisciplinary discussion 2

Prognostic Assessment

DAI grading correlates strongly with outcomes, with Grade III DAI (dorsolateral brainstem lesions) associated with poor outcomes and highest mortality 1, 2. The presence of both a contusion and >4 foci of hemorrhagic axonal injury on MRI is an independent prognostic predictor 1, 2, 3.

Additional prognostic factors include:

• Dysautonomia, hyperglycemia ≥8 mmol/L, and subdural hematoma are associated with higher mortality 4
• Glasgow Coma Scale score <8, secondary systemic injuries score ≥3, hyperglycemia ≥8 mmol/L, and DAI count ≥6 are associated with poor outcome 4
• In patients with pure DAI, absence of consciousness recovery is the unique independent factor of mortality 4

Rehabilitation and Long-term Management

Early physical therapy and rehabilitation are essential to prevent joint contractures and muscle atrophy, including proper positioning, frequent repositioning, range of motion exercises, and splinting 1, 2.

Regular multidisciplinary case reviews are recommended for patients with severe DAI, and early communication with regional neuroscience centers is essential for patients with perceived devastating brain injury 1, 2, 3.

Follow-up imaging is indicated with neurological deterioration rather than on a routine basis 2. Repeat CT is recommended for patients with epidural, subdural, and parenchymal hematomas 2.

Special Considerations

For elderly patients with severe injuries unlikely to be fully recoverable, early insertion of palliative medicine consultation in the decision-making process improves outcomes, reduces in-hospital mortality and length of stay, and improves communication with family 1, 2.

A period of physiological stabilization and observation is recommended for patients with perceived devastating injury to improve the quality of decision making 2.

Common Pitfalls

• Do not rely solely on CT for DAI diagnosis—80% of DAI lesions lack macroscopic hemorrhage visible on CT 3
• The number of microhemorrhages is not currently thought to be associated with injury severity or outcomes, though it helps with accurate diagnosis 2, 3
• Gadolinium-based contrast agents are not necessary for conventional MRI in TBI 3
• DAI primarily stems from rotational acceleration forces during traumatic events, causing widespread axonal disruption 5, 6