There are generally two schools of thought (see below) concerning the degree and type of force needed to cause the triad of injuries used to define SBS. Many believe shaking alone is sufficient to cause traumatic brain injury, while others believe that shaking plus some form of cranial impact is required to cause traumatic brain injury (Ramsey, 2006).

Shaking Alone Can Cause Brain Injury

Many clinicians and researchers believe that most adults possess sufficient strength to shake an infant or toddler to the point of causing intracranial injuries that can ultimately cause death or bodily harm without any form of cranial impact or blunt force trauma. This view first gained a foothold within the medical community in 1974 when physician John Caffey postulated the “whiplash shaken baby syndrome” theory, stating that shaking alone could produce the forces sufficient to cause both subdural hematomas and retinal hemorrhages in small children. Caffey took his theory one step further and stated that finding a subdural hematoma and retinal hemorrhages in an infant with no external signs of cranial trauma was absolutely and exclusively diagnostic of child abuse (Ramsey, 2006).

Shaking Alone Cannot Cause Brain Injury

About 1987 the first skeptics began questioning the accuracy of Caffey’s study and his theory. One of the first was physician Ann-Christine Duhaime, who observed that “while the term shaken baby syndrome has become well entrenched in the literature of child abuse, it is characteristic of the syndrome that a history of shaking in such cases is lacking.”

Duhaime conducted a biomechanical study to determine whether an adult could, by means of shaking alone, exert sufficient force to produce traumatic brain injury in infants. Using infant models, Duhaime and her team subjected proportionately correct models to a series of shaking events, some of which were followed by an impact. Duhaime observed that shaking alone produced at most only a mere fraction of the force the previous studies had determined was required to cause subdural hematomas, retinal hemorrhages, or diffuse axonal injury (Ramsey, 2006).

When the shakers were asked to create an impact by slamming the models’ heads into a fixed object, Duhaime observed that the force produced was 50 times greater than that of shaking alone. As a direct result, Duhaime and her team concluded that “severe head injuries commonly diagnosed as shaking injuries require impact to occur and that shaking alone in an otherwise normal baby is unlikely to cause the shaken baby syndrome.” As a result of this questioning, the view referred to as “shaken impact syndrome” emerged (Ramsey, 2006).

For more on the controversy surrounding SBS, please listen to the following National Public Radio interview in which Norman Guthkelch, a retired pediatric neurosurgeon who is credited with connecting shaking a baby with subdural hematomas. The interview with Guthkelch provides a thought-provoking overview of the issues involved. For early work, see also Guthkelch, 1971, in References. Click here to listen to the interview.