who should visit to doctor in case of headaches?

it is commonly said that all the headaches does require either medicine or most important of all a visit to doctors office but in reality it is not, as there are very few of them that may require immediate attention and doctor advise these may include
a sever sudden headache
a headache that may cause unconsciousness
a headache which may cause stiffness of neck and pain in the mouth and even pain in the ear.
especially those persons should require immediate attentions which are previously headache free and all of sudden he start having the severe headache problem.
so if you are suffering from any of these problems you should contact the doctor ASAP to avoid any further complications.