daughter headaches

My 13 year old daughter out of the blue had a sharp headache followed by vomitting.  Felt better after that happened but now has had a constant headache on left side of her head since Sept 2010.  Most of the time it just knocks her down so bad she can't go to school or function.  We have had all of the scans, test and blood work done but nothing is showing up.  Light, sounds etc don't bother her and the treatments for migraine haven't helped either so we think it is something else.  Could it be nerve related caused from a virus or something?  

[Dr Santos]

Hi,
How is your daughter? What specific diagnostic tests were done already? It is good that the initial scans and blood work were fine. If the medications are not helping, inform her doctor for proper management. She may also benefit from a referral to a neurologist or infectious disease specialist to rule out bacterial infection or immune issues. A viral infection usually resolves spontaneously and if this has been present since September, this is unlikely. Hormone changes associated with adolescence may also be ruled out. Take care and do keep us posted.