According to a recent study published online in the British Medical Journal, those that suffer migraine are at an increased risk of stroke after surgery and hospital re-admission within 30 days of discharge.  The authors of the study go on to quantify the increased risk:

With regard to absolute risks, we predict that 2.4 (95% confidence interval 2.1 to 2.8) ischemic strokes would be seen for every 1000 surgical patients. This risk increases to 4.3 (3.2 to 5.3) for every 1000 patients with any migraine diagnosis. Stratified by migraine with aura status, these numbers are 3.9 (2.9 to 5.0) for migraine without aura and 6.3 (3.2 to 9.5) for migraine with aura.

In total, 10 088 patients in our study sample were readmitted to hospital within 30 days. The 30 day hospital readmission rate was higher for patients with migraine than for those with no migraine (adjusted odds ratio 1.31 1.22 to 1.41). Both migraine with aura (adjusted odds ratio 1.59, 1.33 to 1.91) and migraine without aura (1.27, 1.18 to 1.38) were associated with a higher risk of 30 day hospital readmission compared with patients without migraine.

Source:  British Medical Journal