Diffuse axonal injury is best detected in
The diffuse axonal injury is the result of shearing forces, typically from rotational acceleration Due to the slightly different specific gravities (relative mass per unit volume) of white and grey matter, shearing due to change in velocity has a predilection for axons at the grey-white matter junction, as the name implies. In the majority of cases, these forces result in damage to the cells in a way that causes cell oedema. Imaging featuresThe diffuse axonal injury is characterized by multiple focal lesions with a characteristic distribution: typically located at the grey-white matter junction, in the corpus callosum and in more severe cases in the brainstem CTNon-contrast CT of the brain is routine in patients presenting with head injuries. But it is not terribly sensitive to subtle diffuse axonal injury. The appearance depends on whether or not the lesions are ovely hemorrhagic. Hemorrhagic lesions will be hyperdense and range in size from a few millimeters to a few centimeters in diameter. Non-hemorrhagic lesions are hypodense. They typically become more evident over the first few days as edema develops around them. They may be associated with significant and dispropoionate cerebral swelling. MRIMRI is the modality of choice for assessing suspected diffuse axonal injury even in patients with entirely normal CT of the brain.SWI or GRE sequences, exquisitely sensitive to paramagnetic blood products may demonstrate small regions of susceptibility aifact at the grey-white matter junction, in the corpus callosum or the brain stem. Some lesions may be entirely non-hemorrhagic (even using high field strength SWI sequences). These will, however, be visible as regions of high FLAIR signal. MR spectroscopyMRS can be of benefit in identifying patients with grade I injury which may be inapparent on other sequences. Features typically demonstrate elevation of choline peak and reduction of NAASTAGING, GRADING, AND CLASSIFICATION: The Adams and Gennarelli classification defines mild, moderate, and severe grades of TBI.In mild TBI, lesions are seen in the frontotemporalgraywhite matter interfaces. The injury is designated as moderate when the lobar white matter and corpus callosum are affected. In severe TBI, lesions are present in the dorsolateral midbrain and upper pons. More than half of all TBI cases with DAI are designated as moderate to severe.(Ref: Osborn's Brain: Imaging, Pathology, and Anatomy, page 37)
Non contrast CT
Contrast CT
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Transcranial Doppler
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