Where are most of the numerous hypo-dense focal lesions located and what type of injury do that imply?
They are located at the grey-white matter junction, and are in keeping with diffuse axonal injury.
What other types of traumatic injuries are visible?
Left temporal lobe haemorrhagic contusion, and traumatic subarachnoid blood, best seen in the Sylvian fissure on the left.
In addition to the number of visible lesions, how can diffuse axonal injury be graded?
Can be divided into three grades with increasing morbidity and mortality. Grade I involves grey-white matter interfaces; grade II involves corpus callosum in addition to grade I locations; grade III involves brainstem in addition to grade I and II locations.
How do patients with diffuse axonal injury usually present?
Typically patients who are shown to have DAI have loss of consciousness at the time of the accident. Post traumatic coma may last variable time, and is often attributed to coexistent more visible injury (e.g. cerebral contusions). As such the diagnosis is often not suspected until later, when patients fail to recover neurologically as expected.
In the setting of a normal CT brain and a patient who is failing to wake following closed head injury, what investigation should be carried out?
MRI is the modality of choice for assessing suspected diffuse axonal injury even in patients with entirely normal CT of the brain. Susceptibility weighted imaging (SWI) is particularly sensitive.
Extensive grey-white matter junction regions of abnormality are present, appearing both as petechial haemorrhages and hypodense foci. There is a left anterior temporal pole haemorrhagic contusion, and subarachnoid haemorrhage within the left Sylvian fissure and the sulci of both hemispheres.
Ventricles and basal cisterns are age appropriate.