WIDI - N6) Ventilator dependence 1 week after MVC

N6) Ventilator dependence 1 week after MVC

Review the Learning Outcomes, Hx, PE and Labs, and begin the module with your Provisional Diagnosis. Keep hitting "Next" to move through the module.

Learning Outcomes

Articulate your relationship with the consulting diagnostic radiologists in the evaluation of a patient with altered mental status.
Review the DDx considerations in a patient with altered mental status.
Identify the spectrum of imaging findings in appropriate modalities for evaluating a patient with altered mental status.

History

A 25-year-old male ICU patient was involved in a high-speed motor vehicle collision (MVC) a week ago. He remains intubated and ventilated three days later, with difficulties in weaning him off the ventilator. His initial CT head on admission did not show any significant intracranial abnormalities.

Physical Exam

Vitals: BP: 140/90, HR: 105, RR: 16 (Ventilator Settings: Volume Control, Tidal Volume: 500, Rate: 16, FiO2: 40%, PEEP: 5 cm H2O), Temp: 37.5C, SpO2: 98% on current ventilator settings. Neurological: When sedation is paused, the patient is arousable but not following commands. Limited response to pain bilaterally. GCS: 7 (Eyes: 2, Verbal: 1, Motor: 4).

Labs

None

Provisional Diagnosis

Select the Dx you believe is most appropriate

Traumatic brain injury (TBI)

Post-traumatic stress disorder (PTSD)

Diffuse Axonal Injury (DAI)

Post-concussive syndrome

Conversion disorder

Given the history of the high-speed MVC and the difficulty in weaning the patient off the ventilator, the likely diagnosis is diffuse axonal injury.

Well done. You were correct

Potential Acuity

What is your assessment of the likely acuity for this patient?

Emergent (immediate plan required)

Urgent (plan required within 4 hours)

Routine

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The patient requires routine, but expedited workup.

First Imaging Study

What is the first imaging study you will order?

Repeat CT brain

MRI brain

An MRI of the brain is the most appropriate imaging modality in this case because of its superior sensitivity and specificity in detecting diffuse axonal injury (DAI), which is not usually seen on a CT scan. The MRI is capable of detecting microhemorrhages, a common feature of DAI, which can elucidate the reason for the patient's ongoing neurological impairment and difficulty in weaning from the ventilator.

View ACR Appropriateness Criteria

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Pertinent Imaging Observations

Click on the links below to view images from the study, and assess these key findings as best you can.

MRI head with and without contrast

There is evidence of cerebral edema.

Yes

There is mild cerebral edema as evidenced by the in sulcal effacement. This is secondary to the patient’s traumatic brain injury.

There are abnormal lesions.

Yes

The MRI Brain shows extensive and symmetric foci of hyperintensities on the susceptibility weighted imaging sequence. These findings indicate the presence of paramagnetic blood products, suggesting a diffuse axonal injury. This injury occurs when the brain rapidly shifts inside the skull due to a high-energy impact, leading to widespread axonal shear injury and microhemorrhages in the white matter of the brain.

View Report

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View the full study if you'd like to take a look yourself.

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Second Imaging Study

What is the next imaging study you will order?

T2-weighted MRI with and without contrast

None

No further imaging is required as the diagnosis is confirmed with the MRI.

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What is your Diagnosis now that you have seen the imaging results?

Diffuse axonal injury

Bacterial meningitis

Migraine

Chronic hypertensive encephalopathy

The patient’s presentation and imaging findings are consistent with a diagnosis of diffuse axonal injury.

Current Acuity

Initially, you selected and we suggested acuity.

Has your concern for this patient changed?

Emergent (immediate plan required)

Urgent (plan required within 4 hours)

Routine

The patient requires routine, but expedited workup, considering that they sustained this injury a week ago and because treatment is largely supportive.

Assessment and Plan

Please provide your assessment and plan for this patient

This patient, a 25-year-old male, has a severe traumatic brain injury secondary to a high-speed MVC. An MRI was obtained due to difficulty weaning from intubation following an initial negative CT. The MRI findings are consistent with diffuse axonal injury. The patient should receive supportive care and prevention of secondary injuries. Given his prolonged mechanical ventilation, a tracheostomy and percutaneous gastrostomy (PEG) tube placement should be considered for long-term management. The patient will also require neurorehabilitation.

Lessons Learned:
- Diffuse axonal injury (DAI) occurs due to the shearing forces exerted on axons in the white matter as a result of rapid acceleration, deceleration, or rotational forces at the moment of injury.
- This injury often manifests with loss of consciousness, post-traumatic coma, and dysautonomic symptoms.
- The characteristic distribution of lesions in DAI commonly involves the gray-white junction and the corpus callosum. In more severe instances, there may also be brain stem involvement.
- Given the nature of DAI, initial clinical presentation can be challenging to diagnose using a CT scan, which may yield negative results. Therefore, an MRI is the preferred imaging modality for detecting and assessing suspected cases of DAI.
- DAI management is primarily focused on providing supportive care, prevention of secondary injuries, and neurorehabilitation.
- In patients presenting with a GCS of 8 or lower, intubation and mechanical ventilation are necessary, as these individuals are at increased risk of airway obstruction. The absence of a gag reflex in such cases poses a heightened risk of aspiration, while involvement of the brainstem can compromise respiratory drive and increase the risk of hypoxia.
- Developing cerebral edema is a common occurrence following a traumatic brain injury (TBI), and when severe, it may cause elevated intracranial pressure (ICP), a life-threatening situation that could potentially lead to brain herniation.
- In patients requiring prolonged mechanical ventilation, early intervention with tracheostomy and percutaneous endoscopic gastrostomy (PEG) tube placement can improve patient outcomes.

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