Final answer:
The nurse should tell the child that the CT scan will not hurt and that it is important to stay still during the scan. CT scans are painless and involve a scanner rotating around the body to create detailed images.
Step-by-step explanation:
When preparing a school-age child for a computed tomography (CT scan) to assess cerebral function, the nurse should inform the child that 'The scan will not hurt.' CT scans involve using x-rays to create detailed images of the inside of the body, including the brain, without causing any pain. The scanner will rotate around the child, and it is important for the child to remain still to get clear images. Although a CT scan involves exposure to some radiation, no pain is experienced during the process. Depending on the facility's protocols, sometimes a parent or guardian may be allowed to remain with the child for reassurance, unless there's a specific contraindication.