BMJ  2004;328:720-721 (27 March), doi:10.1136/bmj.328.7442.720


Shaken baby syndrome Pathological diagnosis rests on the combined triad, not on individual injuries

Shaken baby syndrome is a form of physical non-accidental injury to
infants, characterised by acute encephalopathy with subdural and retinal
haemorrhages, occurring in a context of inappropriate or inconsistent
history and commonly accompanied by other apparently inflicted injuries.1 2
Injuries to the neck and spinal cord may also be present. Controversy
surrounds the precise causation of the brain injury, the retinal and
subdural haemorrhages, as well as the degree of force required and whether
impact in addition to whiplash forces is needed.1 3 4 Although most
discussion has concerned fatal injuries of this nature, not all are lethal,
but they may be associated with subsequent neurological disability of
varying severity.

Expert medical evidence about inflicted injury must have scientific
validity, but applying the evidence based criteria appropriate to clinical
practice entails some difficulties.5 In clinical practice medical
management of defined clinical problems can be compared and best practice
distinguished by clinical outcomes. Conversely, in inflicted paediatric
injuries, one is presented with the outcome, investigation follows rather
than precedes that outcome, and the history may be incomplete or
deliberately misleading. A need exists for an impartial and intelligent
assessment, but how may this be achieved in practice?

Because of the serious implications of diagnosing inflicted injury such as
shaken baby syndrome, every case must be evaluated in detail, taking
account of all the circumstances surrounding the injury and considering the
pathological features in full, rather than attempting to evaluate the
significance of each component.

In shaken baby syndrome, it is the combined triad of subdural and retinal
haemorrhage with brain damage, as well as the characteristics of each of
these components that allow a reconstruction of the mechanism of injury,
and assessment of the degree of force employed. The application of
rotational acceleration and deceleration forces to the infant's head causes
the brain to rotate in the skull. Abrupt deceleration allows continuing
brain rotation until bridging veins are stretched and ruptured, causing a
thin layer of subdural haemorrhage on the surface of the brain. This is not
a space occupying lesion; its importance is in indicating the mechanism of
injury. The retinal haemorrhages, which are characteristically extensive,
occupy much of the circumference of the globe and extend through all the
layers of the retina and similarly result from rotational acceleration and
deceleration forces.

The mechanism of brain damage is problematic. Traditional wisdom has
suggested shearing forces operating within the brain substance with
consequent axonal damage.6 Geddes et al, in a careful neuropathological
study of head injuries in children using  amyloid precursor protein
immunostaining, observed that the predominant changes in infants with
evidence of shaking were hypoxic-ischaemic rather than the diffuse axonal
injury seen in older children and adults with fatal head trauma.7 8 These
authors thought that acceleration and deceleration forces might damage the
neuraxis to cause apnoea, with consequent ischaemic insult causing diffuse
cerebral oedema.

Unfortunately, this logical idea was followed in a second paper by the
statement, "Although mechanisms of shaking must vary and nobody really
knows how babies are injured, it may not be necessary to shake an infant
very violently to produce stretch injury to its neuroaxis," a conclusion
that is not supported by data in the paper and that has lead to
considerable controversy among expert witnesses in court.8 It ignores the
evidence for the force required to produce the triad of injuries, in fatal
instances of shaken baby syndrome, obtained from evaluating the other
components. Clearly, if "gentle" shaking were capable of causing fatal
injury, such events would be an everyday occurrence. There is abundant
evidence that minor head trauma, so common in the domestic context, is only
very rarely associated with severe intracranial injury.9-11

Further confusion has been sown by a more recent contribution by Geddes et
al.12 This describes the neuropathological findings in the brains of
infants dying of non-traumatic cerebral hypoxia. Random examination of
sections of dura showed intradural haemorrhage evident only at the
microscopic level. On this basis they thought that all the components
normally indicative of shaken baby syndrome might result from hypoxic
damage alone, dural and retinal haemorrhage being due to brain swelling
consequent on cerebral hypoxia. However, subdural haemorrhage in shaken
baby syndrome is a macroscopic, not a microscopic, finding, and the comment
on retinal haemorrhage has even less foundation in that no examination of
the eyes was made.

As shown by Lantz et al in this issue, even when a particular detail has
been claimed to be pathognomonic of shaken baby syndrome, the diagnosis
should not rest on this feature alone13 (p 754). This careful case study
reinforces the need for meticulous identification of the complexity of the
injury and evaluating the findings against the validity of the explanation
offered. It is also true that retinal haemorrhages can have causes other
than shaking and that space occupying subdural haemorrhages causing death
can occur in witnessed accidental injuries in children.14 However, of the
patients Plunkett described, the youngest was 12 months old, which is
outside the age group in which most cases of shaken baby syndrome occur.14

The pathological diagnosis of shaken baby syndrome requires careful
evaluation of the character and extent of all components of the injury and
should not rest merely on the presence or absence of one or more of the
constituent lesions. The basic triad should have all the necessary features
for confident diagnosis and the conclusion that undue force has been
applied. Damage to the neck or spinal cord is further useful confirmation,
and the presence of gripping injuries, while often absent, can provide
further weight. Other inflicted extracranial injuries provide evidence of
abuse even if they are not contemporaneous with the head injury.

Brian Harding, consultant neuropathologist

Great Ormond Street Hospital for Children, London WC1N 3JH

R Anthony Risdon, consultant paediatric pathologist

Great Ormond Street Hospital for Children, London WC1N 3JH

Henry F Krous, director of pathology

Children's Hospital San Diego, San Diego, CA 92123, USA

Editorial p 719 Clinical review p 754 Letters p 766 Personal view p 775
Competing interests: None declared.


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