From the Guidelines
To differentiate an acute cerebral injury in a person who is speaking well, the most effective approach is a combination of neuroimaging and clinical assessment, starting with a non-contrast CT scan of the brain, followed by MRI with diffusion-weighted imaging, as recommended by the American College of Radiology in their 2021 update 1.
Key Considerations
- The initial non-contrast CT scan is crucial for detecting hemorrhage and other acute injuries that require immediate intervention.
- MRI with diffusion-weighted imaging is more sensitive for detecting subtle findings, such as small cortical contusions, subdural hematomas, and white matter lesions, which can be indicative of traumatic axonal injury or diffuse axonal injury (DAI) 1.
- Clinical assessment tools, like the National Institutes of Health Stroke Scale (NIHSS), are essential for evaluating neurological deficits, while laboratory tests help rule out other causes of symptoms.
- A thorough examination of cranial nerves, motor function, sensation, coordination, and cognitive status is necessary, as preserved speech does not exclude injury to other brain regions.
Imaging Modalities
- Non-contrast CT scan: initial test of choice for acute head trauma due to its rapid availability and ability to detect hemorrhage 1.
- MRI with diffusion-weighted imaging: more sensitive for detecting early ischemic changes, small lesions, and posterior fossa abnormalities, and is recommended for subacute or chronic head trauma with unexplained cognitive or neurologic deficits 1.
Clinical Assessment
- NIHSS: provides standardized evaluation of neurological deficits.
- Laboratory tests: complete blood count, coagulation studies, and metabolic panel help rule out other causes of symptoms.
- Thorough examination of cranial nerves, motor function, sensation, coordination, and cognitive status is essential to detect subtle neurological deficits.
Prognostication
- Early MRI may be of greater value for long-term prognostication, particularly in patients with mild TBI and normal CT scans, as it can detect abnormalities that may be clinically relevant in improving prediction of 3-month outcomes 1.
From the Research
Imaging Modalities for Acute Cerebral Injury
The following imaging modalities can be used to differentiate an acute cerebral injury in a person who is speaking well:
- Computed Tomography (CT) scan: CT allows for rapid assessment of brain pathology and is crucial in assessing the outcome of surgical intervention 2, 3
- Magnetic Resonance Imaging (MRI): MRI provides greater spatial resolution and is more accurate than CT in identifying and characterizing most forms of traumatic cerebral pathology 3, 4
- CT perfusion: CT perfusion can be implemented easily in most hospital centers and provides quantitative perfusion data in addition to structural images 2
- MR angiography: MR angiography can be used to evaluate patients with suspected acute cerebral infarction 5
- Diffusion-weighted MR imaging: Diffusion-weighted MR imaging can be used to evaluate patients with suspected acute cerebral infarction 5
- Cerebral perfusion studies: Cerebral perfusion studies can be used to evaluate patients with suspected acute cerebral infarction 5
Comparison of Imaging Modalities
Studies have compared the effectiveness of different imaging modalities in detecting acute cerebral injury:
- A study found that MRI may be as sensitive as CT scanning in the detection of traumatic head injury, diffuse axonal injury, and intracranial hemorrhage, but missed skull fractures in 5 of 13 patients 4
- Another study found that MRI-based selection for acute ischemic stroke patients is accomplished within a timeframe similar to CT-based selection, without delaying treatment or impacting functional outcome 6
Considerations for Imaging Modalities
When choosing an imaging modality, the following factors should be considered:
- Availability: CT scans are widely available, while MRI may not be as readily available in all hospitals 2, 3
- Time: CT scans are generally faster than MRI scans 6
- Accuracy: MRI is more accurate than CT in identifying and characterizing most forms of traumatic cerebral pathology 3, 4
- Radiation exposure: CT scans involve radiation exposure, while MRI does not 4