Should someone always go to ER if head injury?

How severe. If the injury causes any loss of consciousness, severe or persistent headache, lethargy or weakness the person should be evaluated in an emergency department as soon as possible.
Use common sense. Most head injuries do not involve brain injuries. Go to er for obvious fractures, scalp lacerations, eye injuries affecting vision. Brain injuries with symptoms including loss of consciousness, seizure, weakness, numbness, loss of balance, impaired speech or reasoning are er appropriate. Severe headache even absent other symptoms is reason enough to go to er.