Hannah screamed and went white, and a spectacular egg appeared on the back of her head, but she didn't develop any of the other signs of concussion. But we immediately went home and Rika started dialing around for a hospital, while I googled 'concussion', and quickly learnt about hemotomas, 'talk and die' syndrope and other scary things.
The emergency service provided Rika with a list of hospitals with neurological units. Most were busy with accidents, but on the 4th try, Toho University Ohashi Hospital agreed to look at her. We went down around 11pm.
After a short wait Hannah was seen by a Neurologist. It turned out ??-sensei had studied english in Dunedin () and his professor had worked at the Otago Hospital. He quickly arranged a head x-ray and CAT scan. We took Hannah down to the radiology department where the strapped her onto the bench in front of the donut of the CAT scanner, told her to stay still, and then everyone left the room while she was scanned.
The results were soon available to the neurologist. Fortunately they showed no fracturing of Hannah's skull and no signs of bleeding.
I was immensely relieved to be able to see the pictures and get such a quick confirmation that Hannah would be alright.
But afterwards, when I read-up about CAT scans on Wiki, about I was rather horrified to learn how much radiation Hannah had just received. The typical does for a head CT is 1.5mSv, about 1 years worth of normal background radiation. It is likely the hospital uses a lower dose for children, alhough they didn't give details and we didn't ask. Also estimated lifetime risk of cancer from one scan for a child is just under 1-in-1000. (http://en.wikipedia.org/wiki/X-ray_computed_tomography).
