Shaken Baby Syndrome (SBS) is a non-accidental head injury caused by violently shaking an infant or young child. It is now also referred to under the broader concept of Abusive Head Trauma (AHT).
In 1971, Guthkelch proposed the association between subdural hematoma in infants and shaking injury, leading to the formation of the SBS/AHT concept2).
The incidence is high in infants, with reports varying. The peak age is 2 to 4 months, with most cases occurring in infants under 6 months. It is a serious condition with high risk of death and neurological sequelae6).
The diagnosis of SBS has long been based on a combination of the following three signs.
Retinal hemorrhage
Extensive multilayered hemorrhage: Retinal hemorrhage extending from the posterior pole to the periphery.
Retinoschisis: Dissociation between retinal layers caused by vitreoretinal traction, considered an important finding suggestive of AHT3,7).
Subdural hematoma
Rupture of bridging veins: Bridging veins connecting the cerebral surface and the dural venous sinuses are thought to be damaged by acceleration-deceleration forces.
Bilateral and thin-layer: In the infant brain with poor shock absorption, it often spreads bilaterally.
Encephalopathy
Impaired consciousness and seizures: Reflect secondary damage due to brain parenchymal injury or hypoxia/ischemia. 1)
Poor prognostic factors: Low GCS at admission and diffuse cerebral edema on imaging are associated with poor prognosis.
The absence of external findings, extensive multilayered retinal hemorrhages, and a combination of multiple indicators from the PediBIRN clinical decision rule are used for differentiation. 5) However, it is difficult to make a definitive diagnosis based on a single finding, and a comprehensive evaluation by a multidisciplinary team is necessary.
Infants and young children cannot verbalize symptoms, so interviews with parents or caregivers are important.
The main clinical findings are shown below.
| Finding | Frequency/Characteristics |
|---|---|
| Retinal hemorrhage | Frequently observed in AHT, characterized by extensive, multilayered, and bilateral involvement3,7) |
| Few external findings | Some cases have minimal external trauma and cannot be ruled out by appearance alone1,6) |
| Subdural hematoma | One of the intracranial injuries emphasized in AHT |
Retinal hemorrhage can also occur due to other causes such as accidental head trauma, childbirth, or blood disorders. However, extensive multilayered hemorrhage, bilateral hemorrhage, and hemorrhage extending to the periphery are patterns strongly associated with AHT3,7). Differential diagnosis requires a comprehensive systemic, ophthalmologic, and hematologic evaluation.
The primary injury mechanism of SBS is repetitive acceleration-deceleration force. Because an infant’s head is relatively large compared to body weight and the neck muscles are underdeveloped, violent shaking causes the head to be thrown back and forth with large amplitude.
This action results in the following injuries:
Shaking an infant to try to revive them after loss of consciousness is also dangerous. If there are abnormalities in breathing or consciousness, do not shake the infant; instead, call for emergency medical services and perform basic life support.
Diagnosis of SBS requires ophthalmologic evaluation, neuroimaging, skeletal assessment, and multidisciplinary collaboration.
The core of ophthalmologic evaluation is dilated fundus examination. The distribution, layer, and extent of retinal hemorrhages should be documented in detail. Fundus photography, fluorescein angiography, and optical coherence tomography (OCT) are useful for auxiliary diagnosis.
This is a screening tool for abusive head trauma developed by the Pediatric Brain Injury Research Network (PediBIRN). 5)
It consists of the following four factors.
| Factor | Description |
|---|---|
| Acute respiratory distress | Acute respiratory distress before admission |
| Subcutaneous hemorrhage at TEN sites | Bruising on trunk, ears, or neck |
| Interhemispheric subdural hemorrhage | Interhemispheric SDH/fluid collection on neuroimaging |
| Atypical skull fracture | Skull fracture other than linear or isolated parietal bone fracture |
In the target population, it was reported that the likelihood of AHT is low when all these factors are negative. However, this is not a definitive exclusion tool and must be combined with comprehensive clinical judgment. 5)
Benign External Hydrocephalus (BEH) is an enlargement of the infant head circumference with dilation of the subarachnoid space, and differentiation from SDH is problematic. Diagnosis based solely on the triad has been criticized, and comprehensive evaluation including differential diagnoses and consistency of history is necessary 4).
Criticism of AHT diagnosis based solely on the triad of three signs is rooted in the existence of such differential diagnoses. It is necessary to make a comprehensive judgment including ophthalmological findings, skeletal evaluation, and consistency of history. 4)
The PediBIRN rule is a tool to standardize screening for abusive head trauma. Even if negative, it cannot definitively rule out abuse. Integration with clinical context, consistency of history, and multidisciplinary assessment is essential. 5)
Treatment for SBS is divided into acute systemic management and ophthalmologic management. The fundamental “treatment” is prevention of abuse, and medical management must be combined with social and legal measures.
Acute Systemic Management
Intracranial pressure management: Intensive care for cerebral edema.
Seizure management: Suppression of seizures with antiepileptic drugs.
Respiratory and circulatory management: Management of apnea and circulatory failure. Initial resuscitation determines prognosis.
Ophthalmic management
Observation: Many retinal hemorrhages resolve spontaneously over weeks to months.
Vitrectomy: Consider for complications threatening visual function, such as tractional retinal detachment or vitreous hemorrhage. 7)
Visual function follow-up: Long-term follow-up with attention to amblyopia, strabismus, and visual field defects.
Medical institutions are legally required to report suspected cases of SBS/AHT to child guidance centers or the police (Article 6 of the Act on the Prevention of Child Abuse). Reporting does not require a definitive diagnosis; it can be done at the stage of suspicion.
Repeated acceleration-deceleration forces from shaking apply anteroposterior force to the eyeball. Since the vitreous body in infants is less liquefied than in adults and adheres more firmly to the retina, the vitreous is thought to exert greater traction on the retina.
This traction force particularly causes the following injuries:
Bridging veins that run from the cortical veins on the surface of the cerebrum toward the superior sagittal sinus can be damaged by vigorous head movement. In infants, the relative space between the cerebral cortex and the dura is wider than in adults, and the bridging veins have a longer stretch distance, making them more prone to rupture. Bleeding from a ruptured vein accumulates in the subdural space, forming an SDH.
A critical systematic review has also been published regarding the forensic reliability of AHT diagnosis based solely on the triad of three signs4). The rationale is as follows.
This controversy has promoted the standardization of diagnosis and the establishment of an evidence-based evaluation system, leading to the development of multifactor assessment tools such as PediBIRN. 5)
PediBIRN is a clinical prediction rule developed through a multicenter collaborative study, aiming for high-sensitivity screening to avoid missing AHT5). Challenges include accurate estimation of sensitivity and specificity and confirmation of international applicability. If standardized as a clinical decision rule, it may improve the quality of screening in emergency departments.
Research on remote fundus image reading is progressing as a means to improve access to fundus evaluation in pediatric intensive care units and community hospitals. 7)
Simon (2023) et al. reported cases where retinal hemorrhage was detected even when imaging findings were negative, emphasizing the diagnostic independence of fundus evaluation. 7) Telemedicine-based wide-field fundus camera imaging and remote reading systems may contribute to improved diagnostic accuracy in facilities without resident ophthalmologists.
Shaking an unconscious infant to wake them should be avoided; instead, prioritize calling emergency services and providing basic life support. Forensic evaluation should comprehensively consider the consistency of the history, timing of injury, and medical findings.
The international controversy over the scientific validity of the triad continues. 4) In several countries, including Sweden, there is growing caution about using a triad-only AHT diagnosis as court evidence. Future research requires accumulation of evidence for multifactorial assessment models and formation of an international consensus on diagnostic criteria. 4)
Medical and forensic debate continues over whether abuse can be confirmed solely by the triad of three signs. 4) The existence of differential diagnoses such as benign external hydrocephalus and limitations of experimental evidence are grounds for criticism, and the development of multifactorial assessment tools and unification of international diagnostic criteria are challenges.
There is a high risk of death or severe neurological sequelae (motor impairment, cognitive impairment, epilepsy, visual impairment). Prognosis depends on the degree of initial impaired consciousness, brain edema, and hypoxic-ischemic injury 1,6).
