Please check out #91 and add your wisdom here too. Many of us have been and will be again in such a situation and need to know what to do.
Of course these are irrelevant in this day and age in the United States of America. The current criteria for brain CT appears to be showing up in the ER with a bump. It doesn't matter if there are no specific indications. The CT scan will get ordered and completed to cover the practitioner's ass from a law suit should a given patient with significant injury not happen (however rare) to meet the above criteria.
I'll say it again since the "experts" and pundits seem to not notice. The amount of money spent practicing "defensive" medicine is mind-boggling enormous.