I'm not aware of migraines being a known symptom of high platelets but in the 5 years leading up to my ET diagnosis there was a steady increase in my platelet levels in my annual physical's CBC. My husband, who has had migraines since he was in his 20s (he's 75 now), recently experienced an increase in his migraines with an elevation in his platelets. His count is still well within the normal range for platelets but there does seem to be a correlation.