Allodynia in different forms of migraine

About 60% of patients complain of cutaneous allodynia during migraine episodes, often in the periorbitary region of the pain side. Pre-clinical studies have shown that the underlying mechanism is sensitisation of primary nociceptors and central trigeminovascular neurons and that patients have a lower pain threshold for mechanical stimulation compared to controls. The objective of this study was to determine the prevalence of allodynia during headache attacks in different forms of migraine. The subjects were 221 outpatients consecutively evaluated in the Headache Center of the L. Sacco Hospital in Milan: 114 had only attacks of migraine without aura (MO), 63 had also attacks with aura (MA) and 44 patients with chronic migraine with and without drug overuse (CM). Presence of head allodynia was investigated by a semistructured interview. Statistical analysis was performed by chi square test with Bonferroni correction for multiple comparisons. Forty-seven out of 114 MO patients (41.2%) complained of allodynia during headache episodes, 41 out of 63 MA patients (65.0%), and 29 out of 44 CM patients (65.9%). A higher frequency of allodynia in MA and CM with respect to MO patients was observed (p<0.01 at chi square test). Allodynia was a common complaint in migraineurs, being present in more than 40% patients of each group. A higher frequency was observed in MA and in CM patients. This observation may suggest that both frequency of attacks and presence of aura episodes may contribute to induce changes in neuronal activation threshold thought to sustain allodynia.