If the history and the initial lab work are not revealing, the evaluation should include a CT scan of the head, a chest radiograph, an ECG, and, perhaps, a lumbar puncture. Knowledge gained from a careful history of the event will direct the testing required and urgency of those tests. Detailed questioning should include the duration of the event, color change in the infant, respiratory efforts made by the child, and the intervention required for the episode to cease. Further questions should assess the child's muscle tone, activity, the relationship of the episode to feeding, description of any episodes of emesis, choking or gasping, the presence of fever, and rhythmic movement of the extremities of the eyes. An understanding of the ambient lighting available to the observer may also be helpful. The presence of dried blood in the nose of this small child should prompt the clinician to consider the possibility that this is nonaccidental trauma. Further suspicion is suggested by the family history of SIDS. An EEG and, if available, a pH probe should be done after the urgent studies just described have been obtained. In a younger infant, intercurrent infections such as respiratory syncytial virus (RSV) should also be considered. If nonaccidental trauma is high on the list of possible etiologies, the workup for other concomitant trauma should be pursued with an ophthalmologic examination for retinal hemorrhage and a radiographic skeletal survey for occult fractures.