| Vol. 3, Issue 1, Article 2 |
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Buadu, et al. |
Extra-axial lesions are usually hemorrhagic in nature. Hemorrhage can be epidural, subdural or subarachnoid. Epidural hematomas (EDH) are infrequently encountered in infancy and are particularly uncommon in cases of abuse. They are usually the result of direct impact injuries and are often associated with skull fractures [8]. In contrast, nonaccidental subdural hemorrhage is much more common, usually caused by high energy, angular or rotational acceleration deceleration forces delivered during shaking or shaking impact assaults. Shear strain forces result in disruption of delicate cortical bridging veins as they leave the cortical surfaces to enter the dural venous sinuses. The injury most frequently involves the cortical venous structures draining into the superior sagittal sinus. Consequently, the smallest and earliest collections are encountered in the interhemispheric regions over the cerebral cortices. Because the underlying mechanisms are similar there is a high association of retinal hemorrhages in nonaccidental trauma with SDH. Acute subdural collections are hyperdense on CT. However, subacute or chronic subdural hematomas tend to be of low or mixed attenuation on CT and are better delineated on MR imaging (fig 3a & b). The mechanism of subarachnoid hemorrhage (SAH) is similar to that of SDH resulting from the disruption of cortical veins occurring with angular accelerations or decelerations of the head. In contrast to its high sensitivity for detecting SDH, MRI is relatively insensitive to the presence of hyperacute or acute SAH. Fluid attenuated Inversion Recovery (FLAIR) imaging is, however, quite sensitive and has resulted in improved detection of SAH (fig 4).
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| Subdural Hematoma Fig 3. 5-month-old male child with nonreactive pupils and suspected NAHI. Coronal T1 SPGR image demonstrates a left interhemispheric SDH (fig 3a). A right SDH (arrows) which is less apparent on the TIWI is seen to better advantage on the more sensitive gradient echo image (fig 3b). |
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| Subarachnoid Hemorrhage Fig 4. 9-month-old male presenting with suspected nonaccidental trauma and retinal hemorrhages. Sagittal T1-weighted image shows a right SDH (fig 4a). Axial fluid attenuated inversion recovery image demonstrates SAH (arrows) in the right parietal region (fig 4b). |
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