TRAUMATIC BRAIN INJURY

Imaging

Imaging for optimized detection of traumatic brain injury:

At the time of acute injury, CT is very helpful for the detection of skull fracture, sub-arachnoid and intra-parenchymal blood. MRI is the imaging of choice for assessing the detail of the acute traumatic brain injury, and the long-term structural sequelae in patients who have subsequent epilepsy. MRI should include thin slice volumetric T1-weighted images, axial and coronal T2-weighted and FLAIR images. In acute traumatic brain injury, diffusion-weighted imaging and ADC maps may be required to show areas of ischemia in the first hours after the injury. MRA may be useful to assess for traumatic vessel injury, such as dissection. MR imaging with susceptibility weighted imaging (SWI) or T2* imaging is helpful for detection of hemorrhage.

Imaging characteristics of acute traumatic injury:

• distribution of imaging changes relates to the mechanisms of the traumatic injury, which may be direct blunt trauma causing cerebral contusion, or associated with diffuse axonal shearing
• diffuse axonal shearing appears as small regions of susceptibility artifact on SWI at the grey-white matter junction, in the corpus callosum and brainstem, these also appear as high signal on FLAIR
• cerebral contusions are the result of direct blunt trauma (coup) with the brain coming to a sudden stop against the inner surface of the skull on the opposite side (contrecoup), contusions appear as areas of haemorrhagic change in affected brain areas, with surrounding sulcal effacement and mass effect appearing in the first 24-48 hours (due to edema)
• associated ischemia appears as diffusion restriction, resulting in high signal on DWI and low signal on ADC maps, within minutes from the onset of traumatic brain injury and high signal on T2/FLAIR imaging in the affected area within 6-12 hours

Imaging characteristics of chronic traumatic brain injury:

• atrophy, gliosis, porencephaly/encephalomalacia and ex vacuo dilation of the ipsilateral ventricle in the location of the previous acute traumatic injury.