Diffusion-weighted MRI in shaken baby syndrome
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- Chan, Y., Chu, W.C.W., Wong, G.W.K. et al. Pediatr Radiol (2003) 33: 574. doi:10.1007/s00247-003-0949-y
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We present the characteristic CT and MRI findings of a 2-month-old girl with shaken baby syndrome. Diffusion-weighted MR imaging performed 8 days after the insult established the presence of injury to the white matter in the corpus callosum and subcortical white matter in the temporo-occipito-parietal region. Diffusion-weighted MR imaging is valuable in the diagnostic work-up of suspected shaken baby syndrome, as injury to the white matter can be demonstrated days after the injury.
KeywordsHeadBrainTraumaShaken baby syndromeChild abuseMRIMR (diffusion)
Shaken baby syndrome (SBS) is a serious form of child abuse elicited by violent shaking or shaking with impact. The most common clinical presentation is that of an irritable or abnormally subdued child with difficulty with respiration or cyanotic attacks, frequently accompanied by seizure [1, 2]. Brain imaging is important in the diagnostic work-up of the condition with intracranial lesions characterized by cerebral contusion, subdural and subarachnoid haemorrhage and diffuse cerebral oedema.
The diagnosis of SBS was established by a special investigatory committee. Psychiatric interview of the baby's mother revealed postpartum depression, which was linked to the recent unemployment of the baby's father and tension between the parents. The child was stable in her subsequent course.
SDH is the most common intracranial manifestation of child abuse . SDH signal was mostly low on T1-weighted (T1-W) images and high on T2-W images, suggesting chronic SDH. A focal high signal on T1-W images suggested that re-bleeding had occurred [3, 4, 5]. SDHs were better demonstrated on MRI than CT [3, 5]. Haemorrhages at the vertex, in the subfrontal region, along the tentorium and in the middle and posterior cranial fossae were demonstrated to particular advantage on MRI . The delineation of subdural haemorrhages in the posterior fossa bilaterally on MRI but not on CT in our patient also illustrated this fact.
In child abuse involving vigorous shaking in young babies, white-matter injury similar to diffuse axonal injury observed in accidental trauma, may occur; it is characteristically located at the grey-white junction, centrum semiovale and corpus callosum. MRI detection of diffuse axonal injuries has been shown to be superior to CT , which is also demonstrated by the superior detection of white-matter injury in the right cerebral hemispheric white matter on T2-W MRI in our patient.
DWI has been shown to be of value in diffuse axonal injury in adult patients and is shown as increased signal on isotropic DWI with a corresponding reduction in the apparent diffusion coefficient . DWI in our patient showed greater extent of injury to the cerebral white matter compared to conventional T2-W images. The finding was consistent with the observation by Biousse et al. , who showed that these lesions were larger on DWI than on conventional T2-W MRI in 18 patients aged 6 weeks to 24 months with confirmed SBS. In the present case, lesions in the genu and splenium of the corpus callosum were seen on DWI but not on conventional T2-W images. The hemispheric white-matter lesion was more distinct on DWI.
The biomechanical origin of injury to the white matter in SBS is not fully understood. The high signal on DWI has suggested that cerebral ischaemia plays a major role . In an autopsy series of 14 children with SBS, evidence of axonal injury from immunohistochemical stains for beta-amyloid precursor protein was seen in the cerebral white matter of all cases while swollen axons were present in 11 cases. These changes, however, were also seen in six of seven children dying of non-traumatic hypoxic ischemic encephalopathy. The results suggest that hypoxic/ischaemic injury may partly explain the cerebral axonal injury in SBS .
However, the restricted diffusion on DWI in our patient at least 8 days after injury does not seem to support ischaemia as the only mechanism because ischaemia-induced cytotoxic oedema and reduced apparent diffusion coefficient typically returns to normal about 10 days after infarction. It has been reported that decreased ADC can be seen in adult traumatic shearing axonal injury 18 days after the initial event, which is well beyond that described for cytotoxic oedema in ischaemia . Such a prolonged change may be related to a propagated injury from oxidants or free radicals to which differentiating oligodendrocytes in cerebral white matter seem to be very vulnerable . Delayed neuronal and oligodendroglial cell death from apoptosis in hypoxic ischaemic encephalopathy has been shown in newborn rat models .
In conclusion, the current case illustrates the value of DWI in the detection of white-matter injury in the work-up of suspected SBS. It should, therefore, be incorporated into the MRI examination of all such cases, whether in the acute or subacute stage.