Fact-sheet: Abusive head trauma - Shaken baby syndrome
Updated on 04/23/2019 at 9:43 AM
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Definition
Abusive head trauma - Shaken baby syndrome (AHT-SBS) is a subset of non-accidental head trauma in which shaking alone, or combined with impact, causes the craniocerebral injury.
It is a set of clinical signs affecting infants under one year of age, presenting with subdural hematoma, retinal hemorrhage, or cerebral edema (sometimes referred to as the "triad"), which in most cases indicate that the child has suffered physical violence, either a violent impact (car accident, etc.), or more commonly that the child has been shaken by an adult. This is also referred to as inflicted head trauma. Diagnosis can sometimes be difficult due to the existence of rare conditions that cause similar symptoms, and it remains a subject of controversy.
The act of violent shaking causes abrupt anteroposterior decelerations of the head, resulting in the brain moving back and forth within the skull and tearing of the bridging veins of the convexity.
The shaking may be attributed to a parent overwhelmed by the child's crying; it is actually often much more severe than, for example, a fall from a changing table. The child dies in 10 to 40% of cases, with the majority of survivors left with severe lifelong sequelae, sometimes referred to as "invisible disability."
It is recognized as child abuse, which healthcare providers are required to report in order for an investigation to be conducted, as the recurrence rate exceeds 50% of cases.
It falls within the framework of child abuse (Ambroise Tardieu syndrome, Silverman syndrome).
Sources: Wikipedia article: Shaken Baby Syndrome, HAS guideline: Shaken Baby Syndrome or Abusive Head Trauma from Shaking (July 2017)
Clinical features
Suggestive signs
Difficult diagnosis, underestimated frequency.
Varied and often nonspecific presenting signs: malaise, altered consciousness, seizures, apneic episodes, coma in the most severe cases.
Milder signs: behavioral (painful irritability, sleep disturbance), abnormal pallor (related to anemia), poor bottle feeding, vomiting without diarrhea... which can mislead the diagnosis.
Suggestive findings: bulging fontanelle, increased head circumference, frequent but not constant contusions and bruises (skin, nose, ear, or inside the mouth), fractures occurring before walking age.
Context
Contextual elements that appear unusual or suspicious:
- Adults bringing in their child with delay, or minimizing the symptoms.
- History of unexplained deaths among siblings.
- History inconsistent with the clinical findings.
- Explanations that change depending on the time or the person being questioned.
Laboratory findings
Work-up includes: CBC, hematocrit, electrolytes, lactate level, coagulation studies (platelets, PT, aPTT, fibrinogen, von Willebrand factor, factor VIII, factor IX, factor X), liver enzymes, lipase.
Hematocrit < 30% and/or platelet count above 400 x 10^9/L may be found without explanation.
Radiography
Skeletal survey: performed according to current guidelines. Must be interpreted by a pediatric radiologist. If in doubt, targeted follow-up views should be repeated at day 15.
All types of traumatic lesions may be seen: fractures, periosteal reaction, and callus formation indicating a healing fracture. Rib fractures and metaphyseal corner fractures are the most common findings in abusive trauma.
Ultrasound
Transfontanellar ultrasound: not recommended for the detection of subdural hematomas or subarachnoid hemorrhage (HAS 2017).
Transcranial Doppler ultrasound: allows noninvasive detection of intracranial hypertension and can guide a potential emergency surgical decision.
Abdominal ultrasound: widely recommended depending on clinical findings.
CT
First-line emergency examination, taking care not to exclude the vertex, with bone reconstructions.
Semiology: see MRI
MRI
Brain MRI
Should be performed as soon as the child is stable, ideally within the first week. Of prognostic and diagnostic value when initial CT findings are equivocal.
Minimum protocol: diffusion-weighted imaging, axial and sagittal T1, axial T2, axial T2* sequences. T2 FLAIR sequences allow detection of lesions of different ages.
-Subdural hematomas: multifocal, unilateral or bilateral, involving the vertex, falx, or tentorium cerebelli. Subdural hematomas may initially be masked by cerebral edema.
-Subarachnoid hemorrhage.
-Bridging vein rupture: manifests as clots at the vertex, lateral to the superior sagittal sinus, appearing as oval "tadpole sign" or "lollipop" images, hyperdense on CT or hypointense on T2* MRI.
-Intraparenchymal lesions: anoxic edema, focal or diffuse contusions, or cerebral lacerations (hypointense on T1).
Delayed findings: multicystic encephalopathy, porencephaly, cerebral atrophy.
Spinal MRI:
Protocol: sagittal T1, T2, and axial T2 sequences.
Spinal cord lesions (contusion, hematoma, transection...) and intraspinal subdural hematomas should be sought based on clinical findings (not always associated with vertebral fractures).
Nuclear medicine
Bone scintigraphy: sometimes performed to search for occult bone lesions not visible on radiographs.
Differential diagnosis
Accidental head trauma:
In cases of accidental trauma, the clinical history (explanations from caregivers - parents or the adult responsible for the child) must be consistent and compatible with the observed injuries.
-fall from a low height (adult's Arm, changing table, bed)
A fall of less than 1.5 m (in a child under 1 year of age) cannot cause a multifocal subdural Hematoma, nor diffuse or bilateral retinal hemorrhage. It never results in the association of subdural Hematoma and retinal hemorrhage.
-fall down stairs
-shaking during play
-minor trauma (child bumping into something)
Cannot alone account for the lesions observed in infants under 3 months of age.
-other trauma: birth-related, resuscitation maneuvers...
Other conditions
Do not exclude the possibility of superimposed abuse. Ruled out by clinical examination, coagulation work-up, and imaging.
-Coagulation disorders: thrombocytopenia, Hemophilia, von Willebrand disease, coagulation factor deficiency such as vitamin K deficiency.
-Cerebral arteriovenous malformations. Cerebral aneurysms are exceptional before one year of age.
-Very rare metabolic diseases, such as glutaric aciduria type I or Menkes disease: to be confirmed by specific tests and only if suggestive clinical signs are present.
-Osteogenesis imperfecta: differential diagnosis only applicable to fractures, not to subdural hematomas.
-Benign external hydrocephalus: elevated head circumference (macrocephaly) and enlarged subarachnoid spaces, rare (1 in 100,000), 6% may present with spontaneous subdural hematomas or subdural hematomas following minor trauma. Given the rarity of this condition, the diagnosis of abuse (non-accidental head trauma) should be considered first.