33% of Mig + CRPS and 38% of Mig − CRPS exhibited episodic migraine (EM) while 66% of Mig + CRPS and 62% of Mig − CRPS had chronic migraine (CM) (OR = 0.98, CI 0.36, 2.67). This evidence concerns the gene CXCL9 and complex regional pain syndrome.