Shaken baby synrome (SBS) is a form of child abuse that is thought to occur when an abuser violently shakes an infant or small child, creating a whiplash-type motion that causes acceleration-deceleration injuries. The injury is estimated to affect between 1,200 and 1,600 children every year in the USA. A remarkable feature of SBS is the typical lack of external evidence of trauma. The combination of shaking with striking of the infant against a hard object is sometimes termed the shaken impact syndrome.