Q for medical types: severe headache in 11-year-old

Rajesh sent me a question I'm totally not qualified to answer, but maybe some of you non-American medical types have an idea:

"My son is having headaches for past 2 months.

It is acute throbbing in the fore head, lasts for about 5-10 minutes. Happens one/twice a day. CT scan and EEG reveal no clinical symptoms. Blood report report is also normal. HB is 10.5. TLC/DLC is normal.

He is being treated for migraine for 45 days. The severity of pain has reduced but it is persisting. Now feels weakness in legs and other parts of body too."

Your poor son! This is horrible, and you must feel so helpless.

If the CT scan is normal, I can't think of what could be causing this pain and also the weakness. Anyone with actual medical knowledge have any ideas?