Generally speaking, it is possible for migraine to cause dilated pupil. Migraine is commonly associated with headaches, described as an intense pain of one temple. There are plenty of nerves and vessels in our brain, which is very complicated combination. Some study on migraine said the dilated pupil is caused by Postganglionic sympathetic nerve spasms during migraine. But the dilated pupil is only a temporary symptom, which can disappear without treatment. Actually we know that dilated pupil is related to nervous system. Once nervous system is sitmulated, it is easy to get pupil dilation. Other than migraine, the very common reasons for dilated pupil include drugs, some medications, dark light, fears, excitement, coffee, hormones and so on. Triggers to migraines also include hormones, coffaine, alcohol and so on. Hence you can understand the underlying between them. Hope this could be helpful.
