img.20110067

NEURORADIOLOGY

The importance of neuroimaging in abusive head trauma

1N STOODLEY, FRCR and 2M WILLIAMS, FRCR

1Department of Neuroradiology, Frenchay Hospital, Bristol, UK2Department of Radiology, Craigavon Area Hospital, Portadown, UK

Summary A shaking event is a common mechanism in abusive head trauma (AHT). AHT is associated with greater morbidity and mortality than accidental (usually

impact) head trauma. AHT gives rise to different patterns of subdural haemorrhage (SDH) and

parenchymal brain injury from impact head trauma. Multifocal SDH is best regarded as a marker of a mechanism of injury but does not

itself cause symptoms and signs. Associated parenchymal brain injury leads to symptoms and signs and relates to

outcome. Published standards for the radiological investigation of AHT are available and

should be followed.

doi: 10.1259/img.20110067

2014 The British Institute of

Radiology

Cite this article as: Stoodley N, Williams M. The importance of neuroimaging in abusive head trauma. Imaging 2014;23:20110067.

Abstract. Abusive head trauma (AHT) is best defined asa head injury occurring to a child as a result of an act by a carerthat may be negligent, reckless or deliberate. Whilst there area number of different potential mechanisms involved in AHT,one of the most common is generally (although not universally)accepted to involve shaking; this article will concentrate on thistype of injury and will therefore include AHT that refers toshaking injuries. Over the past decade, we have gained a muchbetter understanding of the nature of such injuries fromdisciplines such as paediatrics, neuroradiology and neuropa-thology, and we are now better equipped to recognize suchinjuries and to intervene when an injury occurs towards thelower end of the spectrum of severity to try to prevent a laterpotentially more serious injury. This is extremely important asthe mortality and morbidity in terms of neurodevelopmentaloutcome of injuries involving shaking are considerably worsethan equivalent accidental injuries (the vast majority of whichare secondary to impact head trauma). Some of the conceptsregarding AHT that were widely held 1015 years ago haveeither been shown not to be true or are not sustainable on thebasis of the current evidence base. This article will reviewthe role of neuroimaging in the diagnosis of AHT in the light ofthe current recommendations for imaging in suspected AHTand will discuss the current state of mainstream opinion in thecontext of everyday clinical experience and the publishedevidence base.

Why bother?

A number of studies suggest that the overall incidenceof subdural haemorrhages occurring as a result of abusivehead trauma (AHT) seems fairly consistent at around24 per 100 0001,2 (a similar incidence to that of all types ofcancer in the infant population). These studies obviouslyonly relate to infants and children who have presented toa hospital and where the treating clinicians have requestedneuroimaging studies, which have subsequently shownappearances consistent with AHT. It is probable that theoverall population incidence of subdural bleeding sec-ondary to a shaking event is greater, as a proportion ofinfants who sustain such an injury are likely to developtransient and non-specific symptoms which resolve spon-taneously and these infants are not presented to a hospital.It is important to remember that the symptoms and signsseen after an episode of AHT are not due to the subduralhaemorrhages but to the associated brain injury. Thecommonest cause of subdural bleeding in infants is beingborn, with MRI studies of normal, completely asymp-tomatic, term infants showing that the incidence of birth-related subdural bleeding varies from 9% to 46%.3,4 Thelowest reported incidence of birth-related subdural bleed-ing follows elective Caesarean section and the highestfollows failed instrumental delivery (forceps and/or ven-touse). Given the current UK birth rate, this equates toa considerable number of babies who have birth-relatedsubdural bleeding that is clinically silent.If birth-related subdural bleeding can be asymptom-

atic, it is likely that subdural bleeding from other causesAddress correspondence to: Dr Neil Stoodley. E-mail: [email protected]

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such as accidental impact head trauma and AHT couldalso be clinically silent (in the absence of any associatedbrain injury). This is an extremely important consider-ation in terms of identifying infants who have sustainedsubdural bleeding as a result of AHT but in whom thereare no current abnormal neurological symptoms or signs:identifying this at-risk group may prevent a subsequentepisode where brain injury does occur with associatedmorbidity and mortality. This is the rationale behindusing head CT as an extension of the skeletal survey toidentify occult injuries.Outcome studies have consistently shown that mor-

bidity and mortality are considerably higher in AHT thanfollowing accidental head trauma.1,5 Most episodes ofaccidental head trauma in children are neurologicallybenign and do not lead to significant long-term prob-lems.6 The difference between these groups seems to bedue to the nature of any associated brain injury: typicaldomestic impact head trauma rarely gives rise to paren-chymal injury; more severe impact head trauma may giverise to focal injuries such as contusions or diffuse axonalinjury, whereas the brain injury seen in cases of AHTinvolving shaking is hypoxicischaemic in nature.7,8

Outcome studies of infants admitted to hospital follow-ing accidental head trauma or AHT with similar degreesof head injury in terms of assessment of the GlasgowComa Score on admission show much higher rates ofdeath and disability in the AHT group.9,10

Patterns of neuroimaging abnormalities

As radiologists, much of our working lives are spentlooking at images and identifying abnormalities andassessing the patterns of those abnormalities in light ofthe clinical information available to construct a differen-tial diagnosis. This approach is as valid in the assessmentof infant head trauma as for anything else that we do.Assuming that our clinical colleagues do not find evi-dence of a naturally occurring medical condition ina child that would account for subdural bleeding, thepresence of subdural haemorrhage is strongly associatedwith head trauma. The types of head trauma that an in-fant may have sustained are birth related, accidental andnon-accidental head injury and different patterns ofsubdural bleeding and of parenchymal brain injury areseen in these groups.

Birth-related subdural bleeding

Although only relatively small numbers of cases havebeen reported, the pattern of birth-related subduralbleeding has been consistent and is reported in the pos-terior fossa and/or over the posterior aspects of the ce-rebral hemispheres adjacent to the falx. In the absence ofan obvious history of significant birth trauma, these aresmall non-space-occupying collections of blood. Birth-related subdural bleeding in normal term infants has notbeen reported over the frontal regions or related to theanterior interhemispheric fissure. Even smaller numbersof babies have been followed up by imaging, but thepublished evidence base suggests that birth-related sub-dural bleeding in this group resolves in terms of scanappearances by 4 weeks of age.3,4

Subdural bleeding as a result of accidentalhead trauma

The vast majority of accidental head trauma occurs asa result of impact, with other mechanisms such as crushinjury occurring less frequently (certainly in the context ofdomestic head trauma). Children are no different fromadults in this respect, and all radiologists will have seensubdural haematomas as a result of impact head injury.Most are of relatively small volume (although occasion-ally we see large space-occupying extradural or subduralhaematomas) but, unless the impact has been very severe,the subdural haematoma is seen at a single site, usuallyrelated to the site of impact (but occasionally diagonallyopposite).The view is sometimes expressed that a significant

degree of force is required to produce a subdural hae-matoma. The absolute degree of force required is notknown, and we do not know the true incidence ofsubdural haematoma following impact head injury asnot all infants and children who sustain a blow to thehead have a CT or MRI scan. However, as the seniorauthor (NS) has been involved in a small number ofcases where an independently witnessed toddler fallfrom standing height has led to the development ofa small acute subdural haematoma, the degree of forcerequired is presumably not necessarily that great(Figure 1).

Subdural bleeding as a result of abusivehead trauma

The typical pattern of acute subdural bleeding in AHT isof shallow (so-called thin film) subdural haematomas thatare most commonly seen in the posterior interhemisphericfissure, posterior fossa and, in contradistinction to birth-related subdural haematomas, over the cerebral convexi-ties. The pattern of subdural bleeding in AHT is in partsimilar to that seen in birth-related bleeding, but mostcases can be differentiated from birth-related bleeding bythe appearance of the blood on scans in terms of the

Figure 1. CT scan showing a single-site acute subduralhaematoma over the right frontal region following anindependently witnessed toddler fall from standing heightonto a carpeted floor.

N Stoodley and M Williams

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assessment of the age of the blood (discussed further be-low). By themselves, these thin-film collections are notspace occupying and do not have any primary effect onthe underlying brain. The significance of these collectionsof blood is therefore their very presence, not their (lack of)effect on the underlying brain, and this means that, be-cause they often appear so insignificant, their huge im-portance as markers of a mechanism of injury is too oftenoverlooked (Figure 2).

Parenchymal brain injury as a result of accidentalhead trauma

Again, the appearances of impact head trauma ininfants and children are similar to those seen in olderchildren and adults, and, so, everyday radiological ex-perience is as relevant as with the topic of subduralbleeding. Significant impact head trauma is of coursevery unusual in the context of non-ambulant infants inthe absence of an obvious history.In terms of brain injury, the two main types seen as

a result of impact head trauma are contusions and diffuseaxonal injury (shearing injury). However, even followingsignificant impact events, such parenchymal injuries arerelatively unusual in the paediatric population (Figure 3).Some years ago, shearing injuries were considered to bethe primary type of brain injury in AHT, but withimprovements in cross-sectional imaging techniques andwith evidence from neuropathological studies involvingcohorts of fatal cases of AHT, such injuries have beenshown to be unusual in AHT unless significant impacthas been involved in the mechanism of injury.7,8

Pattern of parenchymal brain injury in abusivehead trauma

As discussed above, the primary type of brain injury inAHT is hypoxicischaemic in nature. The degree of asso-ciated brain injury is the primary determinant of outcomeand the difference between the types of parenchymal in-jury in accidental and non-accidental head trauma is thelikely reason for the different outcomes in groups whohave sustained brain injuries in these different ways. Caseswhere the pattern and volume of subdural bleeding are

similar have very different outcomes according to the de-gree of associated brain injury (Figure 4).

Assessment of the age of subdural bleeding

As radiologists, we are familiar with the way in whichthe appearance of blood on CT and MRI changes withtime: acute blood is brighter than the underlying brain onCT and becomes progressively darker as it matures suchthat a chronic subdural haematoma is darker than theunderlying brain. What is often not appreciated is that

Figure 2. (a, b) CT scans of two infants admitted with anencephalopathic illness showing thin-film acute subduralhaematomas in the posterior interhemispheric region.

Figure 3. CT scans of three children following impact headtrauma. (a) Image of a 6-week-old child who sustaineda right-sided parietal skull fracture following a witnessedfall from his mothers arms onto a pavement (note theabsence of subdural bleeding or parenchymal brain injury).(b; i, ii) Images of a 4-week-old child who fell approximately90 cm onto a quarry-tiled floor and sustained a left-sideddiastatic parietal skull fracture with extensive soft-tissuescalp swelling but no intracranial haemorrhage or paren-chymal brain injury. (c; i, ii) Images of an 18-month-old childwho fell from a first floor window and sustained a contin-uous left-sided frontal and parieto-occipital skull fracturewith a small amount of acute subdural blood seen adjacentto the left side of the posterior falx but no parenchymalbrain injury.



this only applies to the appearances of discrete collectionsof blood. If blood is mixed with other fluids, such as thecerebrospinal fluid (CSF), then assessment of the age ofthe blood based upon its scan appearances is not valid.This is important in the context of head injury because ifthe arachnoid membrane is damaged at the time of headinjury, CSF can leak into the subdural space and eithercollect there or dilute any acute subdural blood that ispresent.11,12 These mixtures of acute blood and CSF arecalled acute traumatic effusions, and, when they occur,they appear as subdural collections that are darker than

the underlying brain on CT, thus mimicking chronic (orsubacute) subdural haematomas (Figure 5).This is extremely important in the context of AHT, as it

means that, in many of the cases where the initial radi-ology report is of acute and chronic or acute on chronicsubdural bleeds, the subdural abnormalities are actuallydue to the presence of both discrete collections of acutesubdural blood and acute traumatic effusions, i.e. all ofthe subdural abnormalities are likely to have occurred atthe same time rather than as a result of more than oneevent occurring at separate times, weeks apart.The same applies to appearances on MRI scans. Sub-

dural collections that appear of different signal intensities(especially on sensitive sequences such as T2 fluid atten-uation inversionrecovery) are often reported errone-ously as representing blood of different ages. Whilst thatmay be true in terms of discrete collections of blood, if thecollection is actually a mixture of blood and other fluid,then the difference in signal intensity on the same se-quence is more likely to represent the different concen-tration of blood breakdown products within the collection(Figure 6).Acute traumatic effusions are now recognized as being

very common in the context of AHT. It is difficult todifferentiate absolutely between acute traumatic effusionsand chronic subdural haematomas, but imaging pointersare listed in Table 1 and illustrated in Figure 7.

Fractures

In general, the presence of a skull fracture is evidencethat there has been an impact injury to the head ofsufficient severity to lead to the fracture. The com-monest type of skull fracture seen following an acci-dental or non-accidental impact head injury is a simplelinear parietal skull fracture. More complex fracturessuch as those that are diastatic (widened) or depressedare seen more commonly in the context of AHT,13 butit does not follow that simple fractures are due to acci-dental mechanisms and more complex fractures non-accidental; the appearance of the fracture is more likelyto depend on the degree of force causing it than whetherit was accidental or non-accidental.

Figure 4. CT scans of three children following an episode ofnon-accidental head injury showing similar patterns of acutesubdural haemorrhages but different degrees of hypoxicischaemic brain injury. (a) No discernible hypoxic changes andrecovered quickly. (b; i, ii) Diffuse low-attenuation changewith reduced greywhite differentiation and a reversal sign.The child died a few days later despite full intensive caremeasures. (c) Extensive brain infarction (just 3 h after thechild was independently witnessed to be behaving normally).The child died when intensive care measures were withdrawnshortly after the scan was performed.

Figure 5. (a, b) CT scans of an 18-month-old child who wasbeing carried downstairs by a carer. The carer tripped and felland landed on the child, who sustained a depressed right-sided skull fracture, acute extra- and subdural haemorrhagestogether with an intermediate subdural collection anteriorly;an acute traumatic effusion.


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The absolute degree of force required to producea skull fracture in infants and children is not known, and,indeed, we do not know the true incidence of skullfractures following impact head trauma in children, asnot all children who have sustained such injuries haveskull radiographs or scans. Everyday clinical experiencewould, however, suggest that trivial head trauma is un-likely to lead to skull fractures.It is not possible to assess the age of skull fractures

from their radiological appearances as can be done for riband limb fractures; skull bone is different and heals dif-ferently. If there is associated soft-tissue scalp swelling,then it is likely that the causative event will have oc-curred relatively recently but, as soft-tissue scalp swellingcan take some time to develop (or be noticed) and a var-iable time to resolve, accurate assessment of the timing ofan injury by the appearance of soft-tissue swelling is in-herently unreliable. It is also the case that, when soft-tissue bruising or marking is visible clinically, there maynot be any scalp swelling visible on scans, and the

converse is also true in that we do see cases where nosoft-tissue swelling is evident clinically but where diffuseswelling is very obvious on scans. In terms of neurora-diological appearances, most soft-tissue scalp swellingresolves within a 7- to 10-day period, unless there isa significant deep component to the swelling.Fractures are painful, and, so, it is likely that the child

would cry at the time of the causative event, but, in theabsence of any associated brain injury, there may not beany other symptoms or signs until and unless anybruising or soft-tissue scalp swelling becomes evident. Itfollows that the finding of an unexplained fracture ina non-mobile child is potentially of greater significancethan in a mobile child who may have sustained anunwitnessed episode of head trauma.Just as not all dark subdural fluid seen on CT scans

represents chronic subdural haematomas, not all lucen-cies seen on skull radiographs represent fractures, and itis important to be aware of the differential of accessorysutures or congenital fissures. These tend to be short

Figure 6. (a; iiii) CT scans showing uniformly low-attenuation subdural collections over both cerebral convexities due to acutetraumatic effusions. (b) MRI scan sequences from the same patient showing uniform signal collections on T1 (i) and T2 (ii), fluidattenuation inversionrecovery (iii) and T2 gradient echo (iv) sequences.

Table 1. Factors that may help distinguish acute traumatic effusions and chronic subdural haematomas

Acute traumatic effusions Chronic subdural haematomas

Common Fairly uncommon in paediatricsUniform attenuation/signal Areas of different attenuation/signalNo differentiating size: may be large or small No differentiating sizeOften enlarge on sequential early scans Usually do not change significantly in size unless

significant rebleedNo membrane formation/loculation Membrane formation (gives rise to loculation)May be asymmetrical or symmetrical, right vs left May be asymmetrical/symmetrical



linear lucencies perpendicular to the main sutures butdifferentiation is not always clear.14,15

Imaging modalities

As in the imaging investigation of any other condition,the various imaging modalities available to us have boththeir strengths and limitations.

Plain radiographs

The skeletal survey remains an important investigationin possible non-accidental injuries and skull radiographsshould form part of the skeletal survey even when a CTscan of the head has been performed. Fractures that liealong the plane of the scan sections can be missed onstandard CT (Figure 8).

Cerebral ultrasound

Although a very portable imaging modality, the severelimitations associated with its use in this context make itinherently unreliable. As discussed above, the imagingmarker of a shaking injury is of thin-film subdural hae-morrhages over the posterior aspect of the cerebralhemispheres and in the posterior fossa, as well as oftenover the lateral aspects of the cerebral hemispheres; allplaces are not well visualized on ultrasound (Figure 9).Because of this, a normal ultrasound may well be falselyreassuring and, if no other imaging investigations areperformed, this could mean that a child who has

sustained such an injury will, when they have recoveredfrom their presenting encephalopathic illness, be dis-charged back into a potentially dangerous environmentand sustain further injury. Ultrasound has been used in thecontext of detecting parenchymal shearing injuries16 inknown cases of AHT, but it has no role as a screeningexamination.

CT technique

CT is the initial imaging modality of choice, as it iswidely available and accessible, and once a child has beenstabilized following admission, it is relatively straight-forward for them to be scanned. In general, acute sub-dural haematomas over the cerebral hemispheres areeasily visible on CT and, in the small number of caseswhere larger space-occupying haematomas are present,and require urgent neurosurgical intervention, these arereadily identified on CT. Subdural blood in certain sitessuch as the posterior fossa and the subtemporal regionsmay not be as well seen on CT, but it is unusual forsubdural blood to be found in such sites in the absence ofobvious subdural blood elsewhere.CT is generally less sensitive in terms of detecting pa-

renchymal brain injuries, either focal or the more gener-alized hypoxicischaemic brain injury present in manyAHT cases, but such changes are also often obvious onearly scans with features such as the reversal sign. Thehypoxicischaemic changes seen following episodes ofAHT often develop earlier and progress more rapidly

Figure 7. (a) CT and (b) MRI axial T2 and (c) coronal fluidattenuation inversionrecovery sequences showing loculatedchronic subdural haematomas with loculated areas showingfluid with different signal intensities.

Figure 8. (a) Frontal and (b) lateral skull radiographsshowing bilateral diastatic parietal skull fractures.

Figure 9. Ultrasound images illustrating the difficulties ofimaging small volume collections in the subdural space overthe lateral aspects of the cerebral hemispheres (a) and in theposterior fossa (b).


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than in cases of hypoxicischaemic injury caused by non-traumatic events. It is also important to remember that,especially in terms of the brain injury, the appearances atthe time of the scan are just that, a snapshot of what isoccurring at the time of the scan in an evolving patho-logical process. What we are looking at are static imagesof a dynamic process and scans only a few hours apartmay look very different.

MRI technique

MRI has a very important role to play in the in-vestigation of these cases both in the acute phase and inthe longer term. Given its multiplanar capability and theability to use different imaging sequences, it is wellrecognized to be more sensitive than CT in the detectionof parenchymal brain injury of all types, at detectingsmall volume subdural bleeds in sites not well seen onCT and at detecting the small volume subarachnoidhaemorrhages that are very common in AHT (and arethe reason why, when lumbar punctures are performedin these cases, it is very common to find uniformlyblood-stained CSF). Increasingly, MR investigations ofthe spine are being performed at the same time as theacute imaging of the head and spinal haemorrhage hasbeen reported in a significant proportion (approximately5060%) of cases of AHT, most often in the lower tho-racic and lumbar regions17,18 (Figure 10).Given the accepted advantages of MRI over CT, in-

cluding the fact that MRI does not involve the use ofionizing radiation, why not just use MRI? There area number of reasons. Most units outside tertiary centresdo not have the capability to put sick infants with all therequisite monitoring equipment into MRI scanners in anyevent. Most radiologists in the district general hospitalsetting (and many neuroradiologists without paediatricexpertise in teaching centres) would be uncomfortableinterpreting such scans, and it is easier to identify acuteblood on CT than on MRI: the early blood breakdownproducts of oxy- and deoxyhaemoglobin can be verysubtle on MRI sequences, and it is not until meth-aemoglobin develops (which is bright on T1 weightedscans) that blood becomes more obvious on MRI.MRI also has a role in the longer term. As many of the

infants who sustain an episode of AHT are very young, it

can be some time before the likely neurodevelopmentaloutcome will become clear on clinical assessment.Follow-up MRI scanning can give useful prognostic in-formation by identifying areas of permanent structuralbrain damage earlier, which may allow appropriatesupport to be put in place earlier than would otherwisehave been the case.

A rational approach to the imaginginvestigation of possible abusive head trauma

Over the past decade with increased awareness of thenature of AHT and primarily with the more widespreaduse of cross-sectional imaging techniques in head traumaof various types, it has been possible to use a combinationof experience and published literature to formulate rec-ommendations for the imaging investigation of variousaspects of non-accidental injuries, including AHT. A jointworking party of the Royal College of Radiologists,London, UK, and the Royal College of Paediatrics andChild Health, London, UK, published Standards for Radio-logical Investigations of Suspected Non-Accidental Injuryin 2008.19 The approach to neuroimaging recommendedin these guidelines has been subsequently validated bythe results of a systematic review performed by theWelsh Child Protection Systematic Review Group,20

and other papers relevant to AHT from this group havebeen published.21,22 This multidisciplinary group isundertaking systematic reviews in many different aspectsof child abuse and summaries of the results are available atwww.core-info.cf.ac.uk.

Imaging

Initial CT scan

A CT scan of the head should be performed as soon asis reasonably possible following stabilization of thechilds clinical condition if this has been necessary. Thisshould include the whole head from foramen magnum tovertex with a slice thickness no greater than 5mm.Is there evidence of acute (bright) subdural blood? If

so, where? Look carefully at the posterior falx and in theposterior fossa. Does the falx appear brighter than itshould and/or irregular or asymmetrical? If so, there isprobably acute blood lying adjacent to it. Is there anyacute blood over the frontal regions?Look at the CSF in the ventricles and then at the extra-

axial spaces over the cerebral convexities. Is there evi-dence of extra-axial fluid that is darker than the brain butbrighter than the CSF? If so, this is likely to be fluid in thesubdural space (and hence abnormal), but it may not bepossible to tell whether this darker fluid is chronic sub-dural or acute effusion. If you cannot tell, say that youcannot and do not assume that all dark subdural fluid ischronic subdural haematoma (see above).Look at the brain itself. Are there any focal abnor-

malities such as parenchymal haematomas or contusionsor areas of focal low attenuation that might be due todiffuse axonal injury? Look at the overall attenuation ofthe brain and the greywhite differentiation. Althoughthere is less difference between grey matter and un-myelinated white matter in the infant brain than in the

Figure 10. Sagittal T1 (a) and T2 (b) weighted scans of thewhole spine showing high T1 and intermediate to low T2signal blood posteriorly in the lumbosacral region.



brain of an older child or adult, there should still be cleardifferentiation between the grey matter and the whitematter. Reduced attenuation in association with reducedgreywhite differentiation suggests the presence of a de-gree of hypoxicischaemic brain injury.Look at the scan on bone windows. Is there evidence of

a fracture and/or of soft-tissue scalp swelling? Comparethe symmetry of the scalp soft tissues on each side and atthe front and back.Having gone through this process and looked at the CT

images carefully, if the scan appears normal and the childhas no ongoing neurological abnormalities and there areno other features of possible abusive injury (bruises,burns, fractures on skeletal survey, blood in the CSF orretinal haemorrhages), then no further cross-sectionalneuroimaging is required. If, however, the CT scan isabnormal (or any of the above features are found) thenfurther imaging is mandatory and should comprise anMRI scan of the brain and, in the authors view, the wholespine.

Subsequent MRI scan in the acute phase

This scan should be performed within the first few(35) days after admission and may require transfer of thechild to a regional centre. An example of a typical im-aging protocol is given in Table 2.Whilst MRI is more sensitive than CT, as discussed

above, the approach to identifying the abnormalities isnot fundamentally different from that set out above interms of the approach to the CT scan. In addition to goingthrough the same analysis, one also needs to considerother issues for the MRI scan.If there were areas of unequivocally bright blood on

CT, what do those collections of blood look like on T1 andT2 weighted scans? This may allow an assessment of thenature of the predominant blood breakdown productspresent [e.g. intracellular methaemoglobin (bright on T1and dark on T2) vs extracellular methaemoglobin (brighton T1 and T2)]. If there were dark subdural collectionspresent on CT, what do those areas look like on MRI interms of signal on different sequences and have theychanged in size between the scans? Are they of uniformsignal throughout? Are the collections of different signalin different areas and/or is there any evidence of mem-brane formation or loculation? This may help in the as-sessment of whether the collections are more likely to beestablished chronic subdural effusions/haematomas oracute traumatic effusions.Look at the brain parenchyma in the same way as for

the CT scan for evidence of both focal and generalized

abnormalities. Although MRI is more sensitive for thedetection of hypoxicischaemic injury, the changes canstill be subtle and, depending on when the scan is per-formed after the causative event, diffusion-weighted im-aging is not always as helpful as might be thought.Although MRI is not very useful in demonstrating boneinjury, any areas of soft-tissue swelling identified on CTwill need to be assessed on the MRI scan to see how theyhave (or have not) changed.The published evidence base on the topic of spinal MRI

in AHT is currently very limited (but is likely to increasein the near future). On the basis of the published evidenceand current clinical experience, if the spine is imaged thenthe whole spine should be scanned as the commonest sitefor spinal haemorrhage in the context of AHT is inthe lumbosacral region.17,18 It follows that the wholespine needs to be reviewed carefully for evidence of spinalbleeding distant from any intracranial subdural bleeding.

Further imaging in the acute phase

A skeletal survey should be performed as soon as isreasonable. If further neuroimaging is required becauseof ongoing clinical concerns about the childs neurologi-cal status, then the choice of whether to use CT or MRIreally depends on the clinical questions being asked but,from a practical point of view, as long as the initial CTand MRI scans have been performed according to theguidelines then CT will normally suffice.

Longer term follow-up

The imaging guidelines recommend that follow-upMRI should be performed 36 months after the initialinjury primarily to give prognostic information as earlyas possible as discussed above. The imaging protocoldoes not need to be as extensive as on the initial scan anda typical protocol is given in Table 2.

Conclusions

Unfortunately, AHT involving a shaking mechanism isa common clinical problem with a potentially devastatingoutcome for all concerned. Despite our inability to per-form scientific studies of such events on infants, the morewidespread availability and use of cross-sectional imag-ing techniques together with observational studies in thisand other types of head trauma has led to a greater un-derstanding of the condition. The population of infantsthat we see following AHT is no longer limited to thosewho are admitted with obvious external signs of abuse orin whom skeletal surveys show the presence of occultbone injury.Radiologists need to play a full part in the multidisci-

plinary team dealing with these cases and that means (a)recognizing the relevant abnormalities as discussed aboveand (b) reporting those abnormalities in terms of the pos-sibility of them being due to AHT so that an appropriatemultidisciplinary team investigation can occur. Raising thepossibility of AHT in terms of the differential diagnosis ofthe imaging features overall is not the same as gettingembroiled in the forensic process should the case go tocourt, but it might make the difference between a childbeing discharged back into an abusive environment and

Table 2. Typical MRI scan protocols in non-accidental headinjury

Initial MRI scan sequences Follow-up MRI sequences

Sagittal and axial T1 Sagittal and axial T1Axial T2 Axial T2Coronal T2 FLAIR Coronal FLAIRAxial T2 gradient echo/SWI Axial T2 gradient echo/SWIDiffusion-weighted imagingSagittal T1 and T2 whole spine

FLAIR, fluid attenuation inversionrecovery; SWI, susceptibility-weighted imaging.


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a child who does not sustain a further, possibly fatal,injury.

Further reading

This article has concentrated on the imaging aspectsof AHT. For discussion of some of the wider issues re-lated to this topic, there are a number of good reviewarticles available.2326

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