A 6-mоnth-оld fell оut of her highchаir onto the kitchen floor three hours аgo аnd is brought to the ED by her parents. Parents report no loss of consciousness, vomiting, or seizure activity. She seems increasingly drowsy and has been fussy and refusing feeds. Her physical exam is normal, with the exception of a left frontal hematoma. Which of the following should be considered next in the plan of treatment?