Incomplete Posterior Circle of Willis: A Risk Factor for Migraine?

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Migraine is associated with vascular risk factors and white matter abnormalities (WMA). Cerebral hypoperfusion is known to be one mechanism underlying WMA and a few studies have shown that an incomplete circle of Willis (CW) may predispose to cerebral hypoperfusion. This study assessed the relationship between the morphologic characteristics of the CW and migraine.


This case–control study was carried out in the Amiens University Hospital. Patients undergoing 3-dimensional time of flight magnetic resonance angiography of the CW from January 1 to June 30, 2006 were included (n = 124). A definitive diagnosis of migraine was established in 47 patients: 23 (48.9%) experienced migraine without aura and 24 (51.1%) migraine with aura. The remaining 77 patients with other neurologic disorders constituted the control group. The posterior CW was graded as complete when both posterior communicating arteries and the P1 segments of the posterior cerebral artery were present on visual examination and incomplete when one of these vessels was missing (interobserver agreement: Ktotal = 0.746).


Incomplete posterior CW was significantly more common in migraineurs than in the control group (49% vs 18%;P< .001). On multivariate analysis, incomplete posterior CW was the sole independent factor associated with migraine (OR: 6.5; 95% CI: 2.6-16.2;P< .001). No difference was found between migraineurs with and without aura.


Despite some methodological limitations, our results showed that incomplete posterior CW was associated with migraine.

(Headache 2009;49:879-886)

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