“…Results are based on residents of Reykjavik, Iceland, and may not generalize to other populations. Finally, our assessment of TBI did not allow us to evaluate the role of multiple mild head injuries, which have been reported, separately, to be related to both chronic headaches 39 and later parkinsonism. 40 Our finding linking migraine with different indicators of parkinsonism suggests shared cerebral vulnerability that could reflect common pathology, genetic or environmental risk factors, or changes in the brain from one condition that increases the likelihood of symptoms reflecting the other conditions.…”