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. Diffuse Axonal Injuries (DAI)
- 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
Pathology
- 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
Imaging
- 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
References
1. Gentry LR. Imaging of closed head injury. Radiology 1994;191:1-17.
2. Parizel PM, Ozsarlak O, Van Goethem JW, et al. Imaging findings in diffuse axonal injury after closed head trauma. Eur Radiol 1998;8:960-965.
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I had a sub-arachnoid brain hemorrhage, a DAI, and a hemorrhagic stroke in my right central pons after being ejected from a car on the highway. A car ran over my tibia, compound fracturing it, and before I was ejected, we hit the sound wall. I wasn't wearing a seat belt and slammed my face into the B-pillar of the car breaking many ocular bones, a cheek bone, and shattering my nose. We then bounced back into traffic, and the driver side of our car was T-boned by another car. It killed my best friend instantly (Brett Studebaker), and sent me flying out of my open passenger window. Another car stopped a foot from my head. I'm extremely fortunate to be alive today. An inch difference could have easily killed me. I was 20 at the time, and Brett was 19. My recovery has gone very well so far. The accident happened Feb. 6th, 2010. This was a driving under the influence caused accident. Everyone please realize how precious life is, and how easily it can be taken away. God bless, and R.I.P. B.A.S.
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