Also called abusive head trauma, shaken baby syndrome (SBS) is the end result of an infant being violently shaken. It is the main cause of death or neurological injury in infants who are abused. The perpetrators in approximately 90% of all SBS cases are males, typically the biological father of the infants.
Quite frequently, child abuse is under-recognized by respective authorities and the disabling, sometimes subtle, neurological impairment associated with SBS makes diagnosing the condition particularly challenging.
More than fifty percent of infants with SBS at the time of presentation have no previous medical record of abuse, while approximately twenty-five percent of them may have experienced minor trauma in the past.
The violent shaking that causes SBS leads to the destruction of brain cells and respiratory difficulties with ensuing cerebral hypoxia. Edema and subsequent increased intracranial pressure (ICP) followed by ischemia with decreased cerebral perfusion pressure are all results of the hypoxia.
The clinical hallmarks of SBS are retinal and subdural hemorrhages. Subdural hemorrhages are the most common lesions seen in SBS. The ensuing symptoms are mostly due to the increased ICP.
However, there are always some patients who may not show any signs or symptoms of ICP. Less frequently, subarachnoid and intraparenchymal hemorrhages may be seen. Bleeding between the cerebral hemispheres often times is an early and specific sign in SBS.
Infants may present with irritability of extreme proportions, lethargy, vomiting, poor feeding, and/ or appetite, blue or pale colored skin, unconsciousness, convulsions, and coma.
Other clinical features include bruises, tremors, increased head circumference, and bulging fontanelles (i.e. soft spots on the head). Mild symptoms associated with SBS may be so subtle that they go unnoticed or their non-specificity cause them to be overlooked.
Infants who have been violently shaken will appear clinically ill immediately following the trauma to even the most untrained eye. Mild, non-specific signs may persist for some time and may be easily attributed to other etiological factors such as colic, feeding difficulties, or an infectious illness.
Moreover, some signs of previous injury may only become evident after recurrent abusive head trauma. These children may have chronic enlargement of the head and perform poorly in terms of achieving the expected milestones of infancy.
The diagnosis of SBS is confirmed with the identification of retinal hemorrhages, which may be found in one or both eyes. They are usually found together with subdural hemorrhages, because a lesser force is required to produce the latter. Several theories have been postulated for the cause of retinal hemorrhages.
One such theory is the traction injury, which suggests that oscillation of the vitreous and lens causes damage. Another postulates that retinal damage may be a consequence of increased intracranial or intrathoracic pressure.
Abused infants may present with distinctive metaphyseal fractures that occur during shaking.
Fractures of the posterior ribs may occur due to the grip used to hold the child. Up to as many as ninety-five percent of SBS infants may present with skull fractures, particularly of the parietal or occipital bones.
Suspicions should be raised in infants who have depressed bilateral or multiple fractures. It is even more suspicious if these fractures cross suture lines.