My 12 year old son has started experiencing dizziness , nausea, severe headache, and blurry vision . This just started yesterday. Last night he got so dizzy he fell down. These seem to occur as attacks and will get better after 10-15 min. but the headache lingers. He has PDD-NOS , asthma, Tourette s, ADD. Years ago he had a history of petit mal seizures that has gone away. No other significant history. Current meds zyrtec and benadryl . What could be causing this?