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CT and MR imaging of nonaccidental pediatric head trauma
CT and MR Imaging of Nonaccidental Pediatric Head Trauma I Nicola Petitti, MD, PhD, Daniel W. Williams III, MD
Head trauma from child abuse is a major cause of morbidity and mortality. Therefore it is essential for radiologists to understand the manifestation of head trauma from child abuse in various imaging modalities. The authors present the radiologic characteristics of head trauma from abuse-related injuries. The two most useful tools of the radiologist in diagnosing head trauma are computed tomography (CT) and magnetic resonance (MR) imaging. Unexplained complex occipital skull fractures should be considered the result of abuse until proved otherwise. CT is most useful in the evaluation of skull fractures. The presence of multiple subdural hematomas of different ages, in the same or different locations, is indicative of both chronic and acute injuries from repeated abuse. MR is superior to CT for determining the presence and age of subdural hematoma. Subarachnoid hemorrhage, cerebral edema, contusions, diffuse axonal injury, and infarctions are other manifestations of head injury related to abuse. CT is the better method for detecting subarachnoid hemorrhage. Small subdural hematomas, cortical contusions, and shearing injuries are better depicted by MR imaging. By being aware of the radiologic manifestations of nonaccidental trauma, the radiologist can play an important role in the detection and termination of child abuse. Child abuse in the United States is a major cause of morbidity and mortality. The spectrum of disorders that fall under the heading of child abuse include physical, sexual, and emotional abuse, as well as neglect and aban-
Acad Radiol 1998; 5:215-223 1From the Department of Radiology, Bowman Gray School of Medicine, Wake Forest University, Medicai Center Btvd, Winston-Salem, NC 27157-1088, Received September 8, 1997; accepted September 12, Address reprint requests to N,P, © AUR, 1998
donment. From the 1970s until 1997, the number of reported cases of child abuse has increased 150% (1). Because radiologists have the opportunity to diagnose child abuse and thus help treat patients and prevent further harm, it is essential for radiologists to understand the manifestations of child abuse as depicted by various modalities. Radiologists can have the greatest effect on the diagnosis of physical abuse. In such cases, the basic role of radiologic imaging is to help detect abuse-related injuries. If the radiologist determines that a child's injuries are indeed the result of abuse, the proper authorities can be alerted to try to prevent further injuries. In children who are physically abused, the most serious long-term sequelae are from injuries caused by head trauma (2,3). More than 80% of children who die after being abused have experienced traumatic head injuries (4). The severity of the brain injury caused by abuse is greater than the severity of any other type of childhood head injury (5). We present herein the radiologic characteristics of head trauma in abuse-related injuries. The two most useful tools of the radiologist for diagnosing the physical manifestations of pediatric head trauma are computed tomography (CT) and magnetic resonance (MR) imaging.
Causes and Common Findings Head injuries can have many causes, including direct impact, shaking, and strangulation. The shaking injury in particular is characteristic of child abuse. Infants are especially susceptible to a shaking injury because they have not yet developed neck muscles strong enough to support their disproportionately large heads and because their brains are not yet completely myelinated (1). Caffey (6) coined the term "shaken-baby syndrome" to
215
O.
b.
Figure 1. CT scans in an abused 1-year-old boy depict (a) a subgaleal hematoma (arrow) and (b) an underlying linear nondisplaced right parietal bone fracture (arrow).
describe a constellation of findings that indicate this type of abuse. These findings are subdural or subarachnoid hemorrhage; cerebral edema, contusion, or infarction; and retinal hemorrhages. Retinal hemorrhages can be seen in nearly all documented cases of shaking (7). More recently, it has been observed that most shaken children also have impact injuries (8); the term "shakenimpact syndrome" is often used to describe this constellation of findings (1). Because of the long-term effects of hemorrhage, edema, and impact injuries, it is essential for radiologists to understand how to diagnose nonaccidental injury.
Injuries to the Scalp and Face Blunt head injury may produce a subgaleal hematoma (Fig la). In itself, the subgaleal hematoma may not be clinically important, but it can point to an underlying calvarial fracture (Fig lb). Facial fractures are an infrequent but potentially important sign of child abuse; therefore, an inadequately explained facial fracture in an infant should be considered an indicator of abuse until proved otherwise (9). Facial bruising in an infant is also a symptom of abuse and should arouse suspicion. In a study of nearly 400 children who sustained accidental trauma, only 6.5% had facial and neck bruises, compared with 60% of children with nonaccidental injuries (10).
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Injuries to the Calvarium Only 1% of physically abused children have skull fractures at presentation (11); 50% of abused children with an intracranial injury, however, have an associated skull fracture (12). Distinguishing between an accidental skull fracture and one caused by physical abuse may be difficult. There are certain characteristics of a skull fracture that may suggest whether it was accidental. Accidental fractures are usually simple linear fractures that usually involve the parietal bone. A fracture is more likely to be nonaccidental if it has a complex branching pattern, is bilateral, or is more than 5 m m wide (13). If any of these findings is present, a skeletal survey for additional radiographic evidence of physical abuse is warranted. In addition, occipital fractures are more prevalent in nonaccidental injuries (14). In an infant, an occipital bone fracture that is not due to major accidental trauma is virtually pathognomonic of abuse (15) (Figs 2, 3). A commonly reported cause of head trauma in a child is a fall from a sofa or bed. In a review of 246 children who fell out of bed or fell less than 3 feet (90 cm), only three skull fractures were reported. All of the fractures were unilateral and less than 1 mm wide, and none of the children had a serious injury (16). Therefore, in a child who falls from a height of less than 3 feet, no major skull fractures or neurologic findings would be expected. If a
Figure2. CT scan shows soft-tissue swelling over the left posterior parietooccipital region (arrow) with associated c o m m i n u t e d skull fracture in a 2month-old abused f e m a l e infant.
more serious fracture is found, child abuse should be considered the cause until proved otherwise (17). Radiologic evaluation of the skull for possible fracture may be helpful when there is a suspicion of child abuse. CT is better than MR imaging for depicting underlying skull fractures. Although CT is the diagnostic imaging procedure of choice for detecting acute head injury, fractures that are present in the same plane as the CT section may be undetectable. It is therefore important to inspect the scout image that is obtained with the CT study for a skull fracture (Fig 4).
Extraaxial Hemorrhage Epidural hematoma.--Epidural hematoma refers to bleeding within the epidural space. Epidural hematoma has a characteristic biconvex, lenticular shape and rarely crosses suture lines. It can exert a considerable mass effect and often causes neurologic emergencies. Epidural hematomas are, however, a rare manifestation of child abuse (9). In adults, bleeding into the epidural space is from an arterial source (90% of cases involve the meningeal artery) and usually is associated with skull fracture. In children, however, an epidural hematoma is as likely to result from tears of dural veins as from tears of the meningeal arteries (15).
Figure3. CT scan in a 1wear-old boy w h o was rep o r t e d to have fallen out of b e d shows a c o m m i nuted fracture that involves the left parietal region. There is a b o n e f r a g m e n t displaced into the brain parenchyma. Subdural hematoma.--Subdural hematoma is a rare finding in children with accidental injury, but it is the most common manifestation of head trauma in abused children. Only one child was reported to have a subdural hematoma in a study of 536 children who had accidentally fallen less than 5 feet (150 cm) (17). A subdural hematoma is a collection of blood within the subdural space. It is caused by a tear of the bridging veins that extend from the surface of the brain to the dura or to the dural sinus. The usual location of a subdural hematoma is along the cerebral convexity, but it can extend into the interhemispheric fissure. The hemorrhage is visualized as a crescentic peripheral fluid collection within the subdural space. The earliest collections of blood are frequently in the interhemispheric region because a subdural hematoma most often involves the venous structures that drain the sagittal sinus. It is important to differentiate between interhemispheric blood and normally radiographically dense falx seen on head CT scans. A subdurai hematoma has a flat medial border and an irregular lateral border (Fig 5a) and may extend over one tentorial surface (Fig 5b). Secondary signs of subdural hematoma include mass effect on adjacent brain parenchyma. Because acute and chronic blood collections appear different on CT and MR images, a single image may provide evidence of both chronic and acute injuries. If repeated
217
Figure 4. Linear skull fracture (arrows) in an abused 1-year-old boy was d e p i c t e d only on the CT scout scan.
Figure 5. CT scans o b t a i n e d in an abused 8-month-old male infant with a subdural hem a t o m a show (a) increased attenuation along the interhemispheric fissure (arrows), which follows the falx cerebri, and (b) a high-attenuation extraaxial fluid collection layered over the tentorium that represents a subdural hematoma.
,t
b.
episodes of abuse have occurred, multiple subdural hematomas of different ages may be present (in the same or different locations) (Fig 6). An acute hemorrhage into a chronic subdural hematoma produces the "hematocrit effect" as the new blood layers dependently (Fig 7). Subdural hematoma may develop a membrane of granulation tissue along the dural aspect of the lesion (Fig 8). This membrane develops within 2-3 weeks after the hemorrhage. MR imaging is superior to CT in helping to both detect
218
subdural hematoma and determine its age. Depiction by MR imaging of layers of subdural hematomas of different ages is highly suggestive of nonaccidental head trauma (Fig 9). MR imaging may also be useful for differentiating between chronic subdural hematoma and prominent extraaxial cerebrospinal-fluid spaces. Subarachnoid hemorrhage.--A subarachnoid hemorrhage represents blood within the subarachnoid space, cisterns, and ventricles (Fig 10). In infants, subarachnoid
Figure 6. CT scan shows heterogeneous app e a r a n c e of superimposed a c u t e a n d chronic subdural h e m a t o m a s over the right frontal lobe (arrow) in a 14-month-old abused girl. The material with higher attenuation represents fresh bleeding in a chronic subdural h e m a t o m a .
Figure 7.
CT scan shows a subdural hem a t o m a in an 8-month-old abused f e m a l e infant, The large right hemispheric subdural hem a t o m a has a fluid-fluid level (arrow) known as the hematocrit effect.
Intraaxial Injury Contusions and diffuse axonal injury.--Brain contu-
Figure 8. CT scan of an abused 2-month-old f e m a l e infant shows bifrontal extraaxiai fluid collections of varying attenuation represent subacute a n d chronic subdural h e m a t o m a with m e m b r a n e formation (arrows). Also present is a gyral contusional h e m o r r h a g e (arrowhead), hemorrhage is far more common in cases of child abuse than in cases of accidental trauma. Whenever subarachnoid hemorrhage is seen in a child less than 2 years old, child abuse must be considered (18). CT is the best method for depicting subarachnoid hemorrhage.
sions are seen on CT images as focal areas of high attenuation that represent loci of punctate or linear hemorrhage along gyral surfaces. Because contusions occur when the brain contacts a bony protuberance, common locations of contusions include the inferior surface of the frontal lobes and the temporal and frontal poles (Figs 11, 12). The contusion may involve sites distal to the point of impact and may represent a contrecoup lesion, especially if the head is subjected to sudden differential acceleration-deceleration forces as can occur when a child is shaken. An early CT finding is low-attenuation lesions with smaller foci of hyperattenuating petechial hemorrhage. In the 1st few days after the trauma, edema and mass effect can increase, and delayed hemorrhage can occur (19). In the detection of contusions, sensitivity is much greater with MR imaging than with CT, especially in the subacute stage of the injury. MR imaging should be used to detect diffuse axonal injury. This injury is produced by shearing forces induced by sudden acceleration and deceleration or rotational forces on the brain. Lesions caused by diffuse axonal injury are always multiple focal lesions localized to the gray matter-white matter interface, the corpus callosum, and the dorsolateral aspect of the upper brain stem. Dif-
219
a. b. c. Figure 9. MR images of an abused 1-year-old boy. (a) Tl-weighted MR image (500/15 [repetition time msec/echo time]) shows bifrontal extraaxial fluid collections (arrows) with signal intensity slightly greater than that of cerebrospinal fluid and that represent chronic subdural hematoma. (b) Bifrontal extraaxial fluid collections are shown (arrows) on a T2-weighted MR ima g e (3,000/90). (c) Gadolinium-enhanced T1-weighted MR image (500/15) shows dural e n h a n c e m e n t and thickening (arrows) in an abused patient with chronic subdural hematomas.
Figure 10. CT scan in an abused 2-month-old female infant shows blood within the left sylvian fissure (arrow) that represents a subarachnoid hemorrhage. Subacute and chronic subdural hematomas with membrane formation are also shown. Figure 1I. Sagittal Tl-weighted MR image (500/24) of an abused 1-year-old boy that was obtained after he had reportedly fallen shows subdural h e m a t o m a (arrowhead) and contusion (arrow) in the inferior aspect of the frontal lobe.
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Figure 13. Multiple shear injuries are seen in a young boy after involvement in a motor vehicle accident. These lesions are often difficult, if not impossible, to see on (a) standard T2weighted spin-echo MR images (4,000/90) but are easily seen on (b) T2-weighted gradient-echo MR images (arrowheads).
a.
b.
Figure 12. MR image of an abused 1-year-old boy obtained with a gradient-echo sequence (766/25), which is often used to depict blood products (as in this case), shows a contusion of the left temporal pole (arrow).
fuse axonal injury is usually characterized by immediate loss of consciousness and a negative CT scan. This injury is best detected with MR imaging performed with T2weighted or proton-density-weighted sequences (Fig 13). Cerebral edema.--Cerebral edema may result from a
direct blow to the head or from an anoxic injury, such as that caused by strangulation due to occlusion of the carotid artery. Diffuse cerebral edema caused by anoxic injury is the cause of death in most nonaccidental fatalities (9,20). Focal or diffuse manifestations of cerebral edema can be seen with CT and MR imaging. Focal brain edema can exert mass effect on the brain parenchyma. This mass effect can cause compression of the ventricles and perimesencephalic cisterns, as well as effacement of the subarachnoid spaces over the convexities (Fig 14). If the mass effect is severe enough, it can lead to a major shift of midline structures and produce brain herniation. When severe diffuse cerebral edema is present, the cerebral hemispheres show generalized loss of differentiation between gray matter and white matter. This loss of differentiation produces a uniform hypoattenuating appearance throughout the cerebral hemispheres (Fig 15). The basal ganglia, thalami, cerebellum, and brain stem are usually spared and therefore continue to have normal attenuation. Because of the normal attenuation of these regions, they appear hyperattenuating in comparison with the surrounding cortical gray matter and white matter. Because this appearance is the reverse of the normal CT appearance of the brain, this feature has been called the "reversal sign" (21) (Fig 16). In conclusion, major cause of morbidity and mortality in children is head trauma caused by child abuse. It is
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Figure 14. CT scan in an abused 1-year-old boy with a left subdural h e m a t o m a , as well as cerebral e d e m a and infarction represented by diffuse d e c r e a s e d attenuation of the left cerebral hemisphere and d e c r e a s e d gray m a t t e r - w h i t e m a i l e r distinction. The 1c m rightward midline shift and e f f a c e m e n t of the left lateral ventricle are due to the c o m bination of subdural h e m a t o m a and cerebral e d e m a within the left hemisphere. The child died.
very important for the radiologist to recognize the cause of this injury because it is likely to be repeated. In addition, head injuries are often associated with other instances of abuse of the same child or of a sibling. CT is helpful in the diagnosis of head trauma. MR imaging is most useful when the suspicion of abuse is high based on clinical findings but the CT findingS are normal or equivocal (22). For example, nonaccidental injury must be ruled out in any child with severe head injury who does not have a relevant history of accidental trauma (5). Small subdural hematomas, cortical contusions, and shearing injuries are better depicted by MR imaging. Gradient-echo MR imaging is very useful in depicting small areas of hemorrhage because it is able to depict the magnetic susceptibility effects of hemoglobin breakdown products. This information may be especially beneficial in the examination of a child who is believed to have been abused. By being aware of the radiologic manifestations of nonaccidental trauma, the radiologist can have an important role in the detection and termination of child abuse.
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Figure 15. CT scan shows diffuse cerebral e d e m a in an abused 3-month-old infant girl w h o was shaken and strangled. A diffuse decrease in attenuation of the cerebral hemispheres is shown with loss of the subarachnoid spaces in the sylvian fissures a n d over the convexities and loss of the gray m a t t e r - w h i t e matter differentiation, The infant died.
Figure 16. On a CT scan of an abused 3-monthold female infant, the "reversal sign" appears as an area of generalized low aHenuation with loss of the gray m a i l e r - w h i t e maffer differentiation but relative sparing of the basal ganglia and thalamus. Also shown is a posterior interhemispheric subdural h e m a t o m a . The infant died,
!EFERENCE:
1. Brown GR, Runyan DK. Diagnosing child maltreatment. NC Med J 1994; 55:404-408. 2. Merten DF, Osborne DRS. Craniocerebral trauma in the child abuse syndrome, Pediatr Ann 1983; 12:882-887. 3. Merten DF, Osborne DRS, Radkowski MA, Leonidas JC. Craniocerebral trauma in the child abuse syndrome: radiological observations. Pediatr Radio11984; 14:272-277. 4. Bruce DA, Zimmerman RA. Shaken impact syndrome. Pediatr Ann 1989; 18:482-494. 5. Goldstein B, Kelly MM, Bruton D, Cox C. inflicted versus accidental head injury in critically injured children. Crit Care Med 1993; 21:1328-1332. 6. Caffey J. The whiplash shaken infant syndrome: manual shaking by the extremities with whiplash-induced intracranial and intraocular bleedings, linked with residual permanent brain dama g e and mental retardation, Pediatrics 1974; 54:396-403. 7. Carter JE, McCormick AQ. Whiplash shaking syndrome: retinal hemorrhages and computerized axial tomography of the brain. Child Abuse Neg11983; 7:279-286. 8. Gilliland MGF, Folberg R. Shaken babies: some have no impact injuries. J Forensic Sci 1996; 41:114-116. 9. Kleinman PK. Diagnostic imaging of child abuse. Baltimore, Md: Williams & Wilkins, 1987. 10. Roberton DM, Barbor P, Hull D. Unusual injury? recent injury in normal children and children with suspected non-accidental injury, BMJ 1982; 285(6352): 1399-1401. 11. Leonidas JC, Skeletal trauma in the child abuse syndrome.
Pediatr Ann 1983; 12:875-881. 12. Hahn YS, Raimondi A J, McLone DG, Yamanouchi Y. Traumatic mechanisms of head injury in child abuse. Childs Brain 1983; 10:229-241. 13. Brown JK, Minns RA. Non-accidental head injury, with particular reference to whiplash shaking injury and medico-legal aspects. Dev Med Child Neuro11993; 35:849-869, 14. Hobbs CJ. Skull fracture and the diagnosis of abuse. Arch Dis Child 1984; 59:246-252. 15, Bernardi B, Zimmerman RA, Bilaniuk LT. Neuroradiologic evaluation of pediatric craniocerebral trauma. Top Magn Reson Imaging 1993; 5:161-173. 16. Heifer RE, SIovis TL, Black M. injuries resulting when small children fall out of bed. Pediatrics 1977; 60:533-535. 17. Kravitz H, Driessen G, Gomberg R, Korach A. Accidental fails from elevated surfaces in infants from birth to one year of age. Pediatrics 1969; 44(suppl):869-876. 18. Kirkwood JR. Essentials of neuroimaging. New York, NY: Churchill Livingstone, 1990. 19. Osborne AG. Diagnostic neuroradiology. St Louis, Mo: Mosby, 1994. 20. Kleinman PK. Diagnostic imaging in infant abuse. A JR 1990; 155:703-712. 21. Cohen RA, Kaufman RA, Myers PA, Towbin RB. Cranial computed tomography in the abused child with head injury. A JR 1986; 146:97-102. 22. Sato Y, Yuh WTC, Smith WL, Alexander RC, Kao SCS, EIlerbroek CJ. Head injury in child abuse: evaluation with MR imaging. Radiology 1989; 173:653-657,
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Head trauma from child abuse is a major cause of morbidity and mortality. Therefore it is essential for radiologists to understand the manifestation of head trauma from child abuse in various imaging modalities. The authors present the radiologic characteristics of head trauma from abuse-related injuries. The two most useful tools of the radiologist in diagnosing head trauma are computed tomography (CT) and magnetic resonance (MR) imaging. Unexplained complex occipital skull fractures should be considered the result of abuse until proved otherwise. CT is most useful in the evaluation of skull fractures. The presence of multiple subdural hematomas of different ages, in the same or different locations, is indicative of both chronic and acute injuries from repeated abuse. MR is superior to CT for determining the presence and age of subdural hematoma. Subarachnoid hemorrhage, cerebral edema, contusions, diffuse axonal injury, and infarctions are other manifestations of head injury related to abuse. CT is the better method for detecting subarachnoid hemorrhage. Small subdural hematomas, cortical contusions, and shearing injuries are better depicted by MR imaging. By being aware of the radiologic manifestations of nonaccidental trauma, the radiologist can play an important role in the detection and termination of child abuse. Child abuse in the United States is a major cause of morbidity and mortality. The spectrum of disorders that fall under the heading of child abuse include physical, sexual, and emotional abuse, as well as neglect and aban-
Acad Radiol 1998; 5:215-223 1From the Department of Radiology, Bowman Gray School of Medicine, Wake Forest University, Medicai Center Btvd, Winston-Salem, NC 27157-1088, Received September 8, 1997; accepted September 12, Address reprint requests to N,P, © AUR, 1998
donment. From the 1970s until 1997, the number of reported cases of child abuse has increased 150% (1). Because radiologists have the opportunity to diagnose child abuse and thus help treat patients and prevent further harm, it is essential for radiologists to understand the manifestations of child abuse as depicted by various modalities. Radiologists can have the greatest effect on the diagnosis of physical abuse. In such cases, the basic role of radiologic imaging is to help detect abuse-related injuries. If the radiologist determines that a child's injuries are indeed the result of abuse, the proper authorities can be alerted to try to prevent further injuries. In children who are physically abused, the most serious long-term sequelae are from injuries caused by head trauma (2,3). More than 80% of children who die after being abused have experienced traumatic head injuries (4). The severity of the brain injury caused by abuse is greater than the severity of any other type of childhood head injury (5). We present herein the radiologic characteristics of head trauma in abuse-related injuries. The two most useful tools of the radiologist for diagnosing the physical manifestations of pediatric head trauma are computed tomography (CT) and magnetic resonance (MR) imaging.
Causes and Common Findings Head injuries can have many causes, including direct impact, shaking, and strangulation. The shaking injury in particular is characteristic of child abuse. Infants are especially susceptible to a shaking injury because they have not yet developed neck muscles strong enough to support their disproportionately large heads and because their brains are not yet completely myelinated (1). Caffey (6) coined the term "shaken-baby syndrome" to
215
O.
b.
Figure 1. CT scans in an abused 1-year-old boy depict (a) a subgaleal hematoma (arrow) and (b) an underlying linear nondisplaced right parietal bone fracture (arrow).
describe a constellation of findings that indicate this type of abuse. These findings are subdural or subarachnoid hemorrhage; cerebral edema, contusion, or infarction; and retinal hemorrhages. Retinal hemorrhages can be seen in nearly all documented cases of shaking (7). More recently, it has been observed that most shaken children also have impact injuries (8); the term "shakenimpact syndrome" is often used to describe this constellation of findings (1). Because of the long-term effects of hemorrhage, edema, and impact injuries, it is essential for radiologists to understand how to diagnose nonaccidental injury.
Injuries to the Scalp and Face Blunt head injury may produce a subgaleal hematoma (Fig la). In itself, the subgaleal hematoma may not be clinically important, but it can point to an underlying calvarial fracture (Fig lb). Facial fractures are an infrequent but potentially important sign of child abuse; therefore, an inadequately explained facial fracture in an infant should be considered an indicator of abuse until proved otherwise (9). Facial bruising in an infant is also a symptom of abuse and should arouse suspicion. In a study of nearly 400 children who sustained accidental trauma, only 6.5% had facial and neck bruises, compared with 60% of children with nonaccidental injuries (10).
216
Injuries to the Calvarium Only 1% of physically abused children have skull fractures at presentation (11); 50% of abused children with an intracranial injury, however, have an associated skull fracture (12). Distinguishing between an accidental skull fracture and one caused by physical abuse may be difficult. There are certain characteristics of a skull fracture that may suggest whether it was accidental. Accidental fractures are usually simple linear fractures that usually involve the parietal bone. A fracture is more likely to be nonaccidental if it has a complex branching pattern, is bilateral, or is more than 5 m m wide (13). If any of these findings is present, a skeletal survey for additional radiographic evidence of physical abuse is warranted. In addition, occipital fractures are more prevalent in nonaccidental injuries (14). In an infant, an occipital bone fracture that is not due to major accidental trauma is virtually pathognomonic of abuse (15) (Figs 2, 3). A commonly reported cause of head trauma in a child is a fall from a sofa or bed. In a review of 246 children who fell out of bed or fell less than 3 feet (90 cm), only three skull fractures were reported. All of the fractures were unilateral and less than 1 mm wide, and none of the children had a serious injury (16). Therefore, in a child who falls from a height of less than 3 feet, no major skull fractures or neurologic findings would be expected. If a
Figure2. CT scan shows soft-tissue swelling over the left posterior parietooccipital region (arrow) with associated c o m m i n u t e d skull fracture in a 2month-old abused f e m a l e infant.
more serious fracture is found, child abuse should be considered the cause until proved otherwise (17). Radiologic evaluation of the skull for possible fracture may be helpful when there is a suspicion of child abuse. CT is better than MR imaging for depicting underlying skull fractures. Although CT is the diagnostic imaging procedure of choice for detecting acute head injury, fractures that are present in the same plane as the CT section may be undetectable. It is therefore important to inspect the scout image that is obtained with the CT study for a skull fracture (Fig 4).
Extraaxial Hemorrhage Epidural hematoma.--Epidural hematoma refers to bleeding within the epidural space. Epidural hematoma has a characteristic biconvex, lenticular shape and rarely crosses suture lines. It can exert a considerable mass effect and often causes neurologic emergencies. Epidural hematomas are, however, a rare manifestation of child abuse (9). In adults, bleeding into the epidural space is from an arterial source (90% of cases involve the meningeal artery) and usually is associated with skull fracture. In children, however, an epidural hematoma is as likely to result from tears of dural veins as from tears of the meningeal arteries (15).
Figure3. CT scan in a 1wear-old boy w h o was rep o r t e d to have fallen out of b e d shows a c o m m i nuted fracture that involves the left parietal region. There is a b o n e f r a g m e n t displaced into the brain parenchyma. Subdural hematoma.--Subdural hematoma is a rare finding in children with accidental injury, but it is the most common manifestation of head trauma in abused children. Only one child was reported to have a subdural hematoma in a study of 536 children who had accidentally fallen less than 5 feet (150 cm) (17). A subdural hematoma is a collection of blood within the subdural space. It is caused by a tear of the bridging veins that extend from the surface of the brain to the dura or to the dural sinus. The usual location of a subdural hematoma is along the cerebral convexity, but it can extend into the interhemispheric fissure. The hemorrhage is visualized as a crescentic peripheral fluid collection within the subdural space. The earliest collections of blood are frequently in the interhemispheric region because a subdural hematoma most often involves the venous structures that drain the sagittal sinus. It is important to differentiate between interhemispheric blood and normally radiographically dense falx seen on head CT scans. A subdurai hematoma has a flat medial border and an irregular lateral border (Fig 5a) and may extend over one tentorial surface (Fig 5b). Secondary signs of subdural hematoma include mass effect on adjacent brain parenchyma. Because acute and chronic blood collections appear different on CT and MR images, a single image may provide evidence of both chronic and acute injuries. If repeated
217
Figure 4. Linear skull fracture (arrows) in an abused 1-year-old boy was d e p i c t e d only on the CT scout scan.
Figure 5. CT scans o b t a i n e d in an abused 8-month-old male infant with a subdural hem a t o m a show (a) increased attenuation along the interhemispheric fissure (arrows), which follows the falx cerebri, and (b) a high-attenuation extraaxial fluid collection layered over the tentorium that represents a subdural hematoma.
,t
b.
episodes of abuse have occurred, multiple subdural hematomas of different ages may be present (in the same or different locations) (Fig 6). An acute hemorrhage into a chronic subdural hematoma produces the "hematocrit effect" as the new blood layers dependently (Fig 7). Subdural hematoma may develop a membrane of granulation tissue along the dural aspect of the lesion (Fig 8). This membrane develops within 2-3 weeks after the hemorrhage. MR imaging is superior to CT in helping to both detect
218
subdural hematoma and determine its age. Depiction by MR imaging of layers of subdural hematomas of different ages is highly suggestive of nonaccidental head trauma (Fig 9). MR imaging may also be useful for differentiating between chronic subdural hematoma and prominent extraaxial cerebrospinal-fluid spaces. Subarachnoid hemorrhage.--A subarachnoid hemorrhage represents blood within the subarachnoid space, cisterns, and ventricles (Fig 10). In infants, subarachnoid
Figure 6. CT scan shows heterogeneous app e a r a n c e of superimposed a c u t e a n d chronic subdural h e m a t o m a s over the right frontal lobe (arrow) in a 14-month-old abused girl. The material with higher attenuation represents fresh bleeding in a chronic subdural h e m a t o m a .
Figure 7.
CT scan shows a subdural hem a t o m a in an 8-month-old abused f e m a l e infant, The large right hemispheric subdural hem a t o m a has a fluid-fluid level (arrow) known as the hematocrit effect.
Intraaxial Injury Contusions and diffuse axonal injury.--Brain contu-
Figure 8. CT scan of an abused 2-month-old f e m a l e infant shows bifrontal extraaxiai fluid collections of varying attenuation represent subacute a n d chronic subdural h e m a t o m a with m e m b r a n e formation (arrows). Also present is a gyral contusional h e m o r r h a g e (arrowhead), hemorrhage is far more common in cases of child abuse than in cases of accidental trauma. Whenever subarachnoid hemorrhage is seen in a child less than 2 years old, child abuse must be considered (18). CT is the best method for depicting subarachnoid hemorrhage.
sions are seen on CT images as focal areas of high attenuation that represent loci of punctate or linear hemorrhage along gyral surfaces. Because contusions occur when the brain contacts a bony protuberance, common locations of contusions include the inferior surface of the frontal lobes and the temporal and frontal poles (Figs 11, 12). The contusion may involve sites distal to the point of impact and may represent a contrecoup lesion, especially if the head is subjected to sudden differential acceleration-deceleration forces as can occur when a child is shaken. An early CT finding is low-attenuation lesions with smaller foci of hyperattenuating petechial hemorrhage. In the 1st few days after the trauma, edema and mass effect can increase, and delayed hemorrhage can occur (19). In the detection of contusions, sensitivity is much greater with MR imaging than with CT, especially in the subacute stage of the injury. MR imaging should be used to detect diffuse axonal injury. This injury is produced by shearing forces induced by sudden acceleration and deceleration or rotational forces on the brain. Lesions caused by diffuse axonal injury are always multiple focal lesions localized to the gray matter-white matter interface, the corpus callosum, and the dorsolateral aspect of the upper brain stem. Dif-
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a. b. c. Figure 9. MR images of an abused 1-year-old boy. (a) Tl-weighted MR image (500/15 [repetition time msec/echo time]) shows bifrontal extraaxial fluid collections (arrows) with signal intensity slightly greater than that of cerebrospinal fluid and that represent chronic subdural hematoma. (b) Bifrontal extraaxial fluid collections are shown (arrows) on a T2-weighted MR ima g e (3,000/90). (c) Gadolinium-enhanced T1-weighted MR image (500/15) shows dural e n h a n c e m e n t and thickening (arrows) in an abused patient with chronic subdural hematomas.
Figure 10. CT scan in an abused 2-month-old female infant shows blood within the left sylvian fissure (arrow) that represents a subarachnoid hemorrhage. Subacute and chronic subdural hematomas with membrane formation are also shown. Figure 1I. Sagittal Tl-weighted MR image (500/24) of an abused 1-year-old boy that was obtained after he had reportedly fallen shows subdural h e m a t o m a (arrowhead) and contusion (arrow) in the inferior aspect of the frontal lobe.
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Figure 13. Multiple shear injuries are seen in a young boy after involvement in a motor vehicle accident. These lesions are often difficult, if not impossible, to see on (a) standard T2weighted spin-echo MR images (4,000/90) but are easily seen on (b) T2-weighted gradient-echo MR images (arrowheads).
a.
b.
Figure 12. MR image of an abused 1-year-old boy obtained with a gradient-echo sequence (766/25), which is often used to depict blood products (as in this case), shows a contusion of the left temporal pole (arrow).
fuse axonal injury is usually characterized by immediate loss of consciousness and a negative CT scan. This injury is best detected with MR imaging performed with T2weighted or proton-density-weighted sequences (Fig 13). Cerebral edema.--Cerebral edema may result from a
direct blow to the head or from an anoxic injury, such as that caused by strangulation due to occlusion of the carotid artery. Diffuse cerebral edema caused by anoxic injury is the cause of death in most nonaccidental fatalities (9,20). Focal or diffuse manifestations of cerebral edema can be seen with CT and MR imaging. Focal brain edema can exert mass effect on the brain parenchyma. This mass effect can cause compression of the ventricles and perimesencephalic cisterns, as well as effacement of the subarachnoid spaces over the convexities (Fig 14). If the mass effect is severe enough, it can lead to a major shift of midline structures and produce brain herniation. When severe diffuse cerebral edema is present, the cerebral hemispheres show generalized loss of differentiation between gray matter and white matter. This loss of differentiation produces a uniform hypoattenuating appearance throughout the cerebral hemispheres (Fig 15). The basal ganglia, thalami, cerebellum, and brain stem are usually spared and therefore continue to have normal attenuation. Because of the normal attenuation of these regions, they appear hyperattenuating in comparison with the surrounding cortical gray matter and white matter. Because this appearance is the reverse of the normal CT appearance of the brain, this feature has been called the "reversal sign" (21) (Fig 16). In conclusion, major cause of morbidity and mortality in children is head trauma caused by child abuse. It is
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Figure 14. CT scan in an abused 1-year-old boy with a left subdural h e m a t o m a , as well as cerebral e d e m a and infarction represented by diffuse d e c r e a s e d attenuation of the left cerebral hemisphere and d e c r e a s e d gray m a t t e r - w h i t e m a i l e r distinction. The 1c m rightward midline shift and e f f a c e m e n t of the left lateral ventricle are due to the c o m bination of subdural h e m a t o m a and cerebral e d e m a within the left hemisphere. The child died.
very important for the radiologist to recognize the cause of this injury because it is likely to be repeated. In addition, head injuries are often associated with other instances of abuse of the same child or of a sibling. CT is helpful in the diagnosis of head trauma. MR imaging is most useful when the suspicion of abuse is high based on clinical findings but the CT findingS are normal or equivocal (22). For example, nonaccidental injury must be ruled out in any child with severe head injury who does not have a relevant history of accidental trauma (5). Small subdural hematomas, cortical contusions, and shearing injuries are better depicted by MR imaging. Gradient-echo MR imaging is very useful in depicting small areas of hemorrhage because it is able to depict the magnetic susceptibility effects of hemoglobin breakdown products. This information may be especially beneficial in the examination of a child who is believed to have been abused. By being aware of the radiologic manifestations of nonaccidental trauma, the radiologist can have an important role in the detection and termination of child abuse.
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Figure 15. CT scan shows diffuse cerebral e d e m a in an abused 3-month-old infant girl w h o was shaken and strangled. A diffuse decrease in attenuation of the cerebral hemispheres is shown with loss of the subarachnoid spaces in the sylvian fissures a n d over the convexities and loss of the gray m a t t e r - w h i t e matter differentiation, The infant died.
Figure 16. On a CT scan of an abused 3-monthold female infant, the "reversal sign" appears as an area of generalized low aHenuation with loss of the gray m a i l e r - w h i t e maffer differentiation but relative sparing of the basal ganglia and thalamus. Also shown is a posterior interhemispheric subdural h e m a t o m a . The infant died,
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