What are we trying to measure? The problems of case ascertainment

To determine the incidence of a particular phenomenon, one has to know how that phenomenon is defined. The term "shaken baby syndrome" (SBS) came into general usage in the 1980s, followed by shaken impact syndrome (SIS), inflicted childhood neurotrauma, abusive head trauma (AHT), inflicted traumatic brain injury (inflicted TBI), non-accidental head injury (NAHI), and others. Several means of defining this clinical syndrome have been suggested. Keenan has proposed a research definition. Minns has offered a pure clinical definition, and Livingston and Childs suggest a definition that combines the clinical and radiologic features with the history of events leading to the condition. By using these definitions, eight articles describing SBS, published in the last 20 years, were analyzed for these characteristics. A definition of shaken baby syndrome reflecting the common themes in these clinical reports is offered.