Yes, there's probably something similar going on behind the scenes in our brains that can cause both migraine and bipolar symptoms. They're both cyclical expressions, both highly related to sleep & circadian rhythm, often respond to similar treatments, are both genetic, and sufferers of both have similar traits (emptahy, hypersensitivity). The medical literature out there appears to suggest 50% correlation and I did an informal poll here a few weeks ago where around 65-75% of responders had both.

When I was first diagnosed with chronic migraine (what was then called "transformed migraine" where the symptoms seem so different from the original episodes that the connection isn't immediately apparent), I remember finding out that it's genetically related to bipolar, schizophrenia, epilepsy, and restless leg syndrome, all of which appears to be in my extended family.