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Brain Contusion Imaging

Practice Essentials

Brain injury is often defined differently in published reports. Although many authors use the term brain injury to mean acute traumatic damage to the central nervous system (CNS), others use the term head injury, which allows inclusion of skull injuries, fractures, or soft tissue damage to the face or head without any obvious neurologic consequences. Kraus et al defined brain injury as “physician-diagnosed physical damage from acute mechanical energy exchange resulting in concussion, hemorrhage, contusion, or laceration of the brain.”
Brain contusions commonly are identified in patients with traumatic brain injury (TBI) and represent regions of primary neuronal and vascular injury.
Contusions are formed in 2 ways: direct trauma and acceleration/deceleration injury.

Preferred examination

CT scanning is the preferred acute imaging modality, because scans can be performed quickly; newer CT scanners can complete a scan within 5 minutes, with virtually no motion artifacts. CT scan findings help identify abnormalities that may need acute intervention. CT scanning can be performed in the presence of life support equipment.
 

According to the ACR Appropriateness Criteria for Head Trauma, noncontrast head CT scanning is the most appropriate initial modality for acute closed head injury.

However, with CT scans, the true volume of neuronal damage in the contused tissue can be underestimated, and the detection of superficial contusions using CT scans is hampered by artifacts from adjacent bone.

Magnetic resonance imaging (MRI) is more sensitive and accurate than CT for detecting contusions because of its multiplanar capability and greater sensitivity for edema.
Imaging findings in brain contusions tend to vary because of the stages of evolution common to these lesions. Initially, CT findings can be normal or minimally abnormal because the partial volumes between the dense microhemorrhages and the hypodense edema can render contusions isoattenuating relative to the surrounding brain.

MRI findings typically demonstrate the lesions from the onset of injury, but many facilities cannot perform MRI on an emergent basis. In addition, MRI examination can take up to an hour to perform, and patients may require sedation to minimize motion artifacts. Not all hospitals have MRI-compatible life-support devices, and the patient’s body habitus must be physically compatible with the size of the machine.

According to the ACR Appropriateness Criteria, MRI is the most appropriate initial exam for subacute to chronic traumatic brain injury.
 For suspected intracranial vascular injury, CT angiography or venography or MR angiography or venography is considered the most appropriate imaging study.
 In cases of suspected posttraumatic CSF leaks, high-resolution noncontrast skull base CT is the most appropriate initial study.

Skull radiographs are notoriously unhelpful in predicting underlying brain injury. However, scalp hematomas or skull fractures are usually good indicators of a significant direct force to a focal region. As such, the radiographic findings are usually associated with underlying brain contusions, although significant brain injury may occur without these findings. The rate of false-negative findings in skull radiographs is high, but few false-positive findings occur.

Neuroimaging techniques currently under development for evaluation traumatic brain injury include diffusion tensor imaging, functional MRI, and MR spectroscopy (MRS).

(See the diagram and images of brain contusion below.)

Schematic diagrams of contusion locations in sagit

Schematic diagrams of contusion locations in sagittal midline (A), lateral (B), and base (C) views show the areas most commonly affected by contusions (red) and those that are occasionally affected by contusions (blue). Areas that are predominantly affected by contusions include the orbitofrontal cortex, anterior temporal lobe, and posterior portion of the superior temporal gyrus area, with the adjacent parietal opercular area. Areas that are less commonly affected include the lateral midbrain, inferior cerebellum and adjacent tonsil, and the midline superior cerebral cortex.

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Acute brain contusion. Axial CT scan obtained in a

Acute brain contusion. Axial CT scan obtained in a patient immediately after a high-speed motor vehicle accident demonstrates a large, right frontal contusion with hemorrhage and surrounding edema. A smaller, subtle, right temporal cortical contusion (short arrow) is noted, as well as a small, left frontal subdural hematoma (long arrow).

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Acute gliding brain contusions. Axial CT scan obta

Acute gliding brain contusions. Axial CT scan obtained immediately after blunt trauma to the left convexity of the skull resulted in severe swelling of the entire left cerebral hemisphere with loss of the gyral pattern secondary to edema. A small collection of subarachnoid blood is present (up arrow). The right hemisphere shows contrecoup gliding contusions (down arrows).

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Comparison of a CT scan with a xenon blood-flow ra

Comparison of a CT scan with a xenon blood-flow radionuclide scan. (A) CT scan shows bifrontal contusions following severe head trauma (arrows). (B) Companion CT scan showing xenon uptake demonstrates dark regions (arrows), indicating decreased perfusion in the contused brain.

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Surgical resection of the contused brain tissue is indicated when the patient has brain swelling that increases the intracranial pressure above an acceptable degree. Alahamadi et al performed a study to identify the factors that predict radiologic and clinically significant progression of brain contusions in patients who did not originally require surgery and underwent conservative treatment. Of 98 patients studied, 44 had significant progression on computed tomography (CT) scans and 19 required surgery.
In a study of patients with severe head injury due to blunt trauma, 50.8% of patients survived their injury and 13.2% achieved a good functional outcome at 6 months of follow-up.

See Can’t-Miss Findings on Noncontrast Head CT, a Critical Images slideshow, to identify several different abnormalities depicted in noncontrast CT studies.

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