There is a high incidence of mortality and morbidity after inflicted head injury, and it is the most common cause of traumatic death in infancy (34). It has been generally accepted from research evidence that serious or fatal injury from accidental injury, other than that sustained in road traffic accidents or falls from major heights, is rare in children under 2 years and that simple skull fractures in accidental trauma have a low risk of intracranial sequelae (26).
The major acute intracranial lesions of NAI are subdural hematoma, cerebral edema with hypoxic ischemic encephalopathy, and, more rarely, brain lacerations, intracerebral and intraventricular hemorrhage, and extradural hematomas (26).
The mechanism of brain injury is considered to be a whiplash motion of acceleration and deceleration, coupled with a rotational force, during a shaking episode of an infant, where the head is unsupported. Shaking alone may lead to brain injury, although in many instances there may be other forms of head trauma, including impact injuries (35,36). Impact may be against a hard surface, leading to external injury and an associated skull fracture, or against a soft surface, with no associated external injury. Hypoxia may also lead to brain injury from impairment of ventilation during chest squeezing, suffocation, or strangulation (26).
Retinal hemorrhages are strongly suggestive of abuse when accompanied by intracranial injuries and in the absence of a confirmed history of severe accidental injury. Unilateral or bilateral retinal hemorrhages are present in 7590% of cases of shaken baby syndrome (36). Retinal hemorrhages can also be found after severe closed chest injury, asphyxia, coagulation disorders, carbon monoxide poisoning, acute hypertension, sepsis, meningitis, and normal birth (usually disappearing by 2 weeks, rarely persisting to 6 weeks). When shaking injuries are suspected, retinal examination is essential and should include direct and indirect ophthalmoscopy preferably by an ophthalmologist. Subhyaloid hemorrhages and local retinal detachment occur earliest, are often peripheral, and are found only by indirect ophthalmology. When intraocular injury is present, subdural hemorrhage is likely, and the presence of retinal detachment and multiple hemorrhages may indicate additional cerebral lacerations or in-tracerebral hemorrhages (35).
Children with acute intracranial injury may present with fits, lethargy, irritability, apnea, unconsciousness and signs of shock, a tense fontanelle, increasing head circumference, and low hemoglobin. Children with chronic subdural hematomas may present with poor feeding, failure to thrive, vom iting, increasing head circumference, and fits. The presentation may suggest sepsis, meningitis, encephalitis, or toxic or metabolic bone disease. The findings of retinal hemorrhages, other signs of abuse, and blood-stained cere-brospinal fluid may assist with the differential diagnosis. Milder forms of shaking may go undetected or present with nonspecific signs that may be minimized by physicians or attributed to a viral illness (36).
When brain injury of abuse is suspected, a full blood count, platelet count and coagulation studies, skull X-ray, skeletal survey, and brain computed tomography (CT) are recommended. Magnetic resonance imaging (MRI) should be undertaken when CT is equivocal or normal and there are neurological signs or symptoms (26). The American Academy of Pediatrics considers MRI as complimentary to CT and recommends MRI 2-3 daysl later, if possible (36).
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