Trauma and Child Abuse

As noted above, CT is the modality of choice for initial imaging of head and spinal trauma. However, if the findings on CT cannot fully account for the severity of an injured child's neurological deficits, additional evaluation with MRI is indicated. The scout CT image must be scrutinized to exclude skull fractures that are parallel to the transaxial plane of imaging and therefore are imperceptible on transverse images (Fig. 1). Brain, bone and, if possible, subdural windows should be used for interpretation of the study to detect hemorrhages, herniation, parenchymal injuries, fractures and overlying soft tissue injuries.

Acute hemorrhage is hyperdense on CT and variable on MR depending on the state of hemoglobin, but most often T1 hyperintense and T2 hypointense (intracellular methemoglobin). Intracranial bleeds are divided into four types: epidural, subdural, subarachnoid and intraparenchymal. Epidural hematomas are typically related to skull fractures and laceration of an underlying artery (usually the middle meningeal artery) or a dural vein. They are well-defined lentiform extra-axial hyperdense collections (Fig. 2). Subdural hematomas occur as a result of tearing of cortical veins that bridge the subdural space. These are typically

Figure 1. Skull fracture. Transaxial linear lucency in frontal bone on lateral scout image.

Figure 2. Epidural hematoma with significant mass effect. (transaxial CT)

hyperdense crescentic extra-axial fluid collections when acute, isodense to brain parenchyma when subacute (1-2 weeks old) (Fig. 3), and hypodense when chronic (>2-3 weeks old). Administration of intravenous contrast may help confirm a subacute or chronic subdural hematoma, since their outer and inner membranes will enhance due to the presence of granulation tissue. Acute subarachnoid hemorrhage (SAH) is frequently identified in conjunction with parenchymal injuries, and reveals itself as hyperdense acute blood along the cerebrospinal (CSF) spaces. SAH is commonly observed in the Sylvian fissures, interpeduncular and perimesencephalic cisterns, sulci along the convexity, and occipital horns of the lateral ventricles and fourth ventricle. MR fluid-attenuated inversion-recovery (FLAIR) images are also sensitive for detecting acute and subacute SAH, which is hyperintense.

Parenchymal hemorrhages are occasionally seen in association with cerebral contusions, which when nonhemorrhagic appear as hypodense areas of brain parenchyma (Fig. 4). Injuries resulting from rotational forces cause shear injuries that appear as ill-defined foci ofT2 hyperintensity. They can also be hyperintense on T1-WI and/or hypointense on T2-WI and gradient recalled echo (GRE) sequences if blood products are present. Usual locations of axonal shear injury include the junction of gray and white matter, the centrum semiovale, the corpus callosum and the brainstem.

Cases of nonaccidental head trauma or child abuse have similar imaging findings as other causes of head trauma. The most common findings include subdural and subarachnoid hemorrhages, cerebral contusions and skull fractures that may be of varying ages. Contusions in the orbital surfaces of the frontal lobes are characteristic, and axonal shearing injuries and infarcts can also be seen. The clinical presentation of these children is highly variable. Often their injuries are incompatible with the reported mechanism, or they may present with excessive irritability, lethargy, failure to thrive, seizures, recurrent encephalopathy or developmental delay.

Figure 3. Acute subdural hematoma. (transaxial CT)

Figure 4. Bilateral cephalohematomas with underlying fractures. Hyperdense parenchymal hemorrhages with surrounding edema. Adjacent subarachnoid blood. (transaxial CT)

Figure 3. Acute subdural hematoma. (transaxial CT)

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