Figure 1: Axial FLAIR MR image shows several high signal foci (arrows and arrowhead) in the gray-white junction of the left frontal lobe in this patient status post closed head trauma (day 1 after trauma). Similar lesions are also seen in the basal ganglia.
Figure 2: Axial GRE MR (susceptibility) image shows two foci demonstrating susceptibility artifact (dark signal intensity, arrows) representing blood products. Another focus (arrowhead) shows minimal to no susceptibility, which may represent a non-hemorrhagic lesion.
- One of the most common primary traumatic brain injuries in patients with severe head trauma (up to 48% in one series)
- Specific pattern of post traumatic diffuse degeneration of the white matter, attributed to prior shearing injury of the white matter
- Impaired consciousness is usually greater in patients with DAI than in patients without DAI
- Frequent cause of poor clinical outcome in patient with head injuries
- Only some lesions are evident on autopsy as small, focal traumatic lesions.
- Many can be visualized only on microscopic examination as multiple axonal retraction balls (pathologic hallmark) and perivascular hemorrhage
- With time, there are microglial and astrocytic reactive changes, endothelial proliferation and accumulation of hemosiderin-laden macrophages at the site of axon disruption
- Three common locations: lobar white matter, corpus callosum, dorsolateral brainstem
- MRI much more sensitive than CT for detection and characterization of DAI lesions
- Multiple, small, deeply situated, elliptical lesions sparing the overlying cortex
- Lesions may be hemorrhagic or non-hemorrhagic (the latter is more common) (CT will easily overlook non-hemorrhagic lesion and small hemorrhagic petechial hemorrhage)
- High signal intensity on T2WI, FLAIR (FLAIR more sensitive)
- Dark signal intensity on susceptibility MR sequence (i.e. T2* GRE) of hemorrhagic lesions