de Tommaso M, et al. - In this observational, open-label, cohort study, researchers assessed the long-term outcome of allodynia in the chronic migraine (CM) group treated with onabotulinumtoxin A (OBT-A) and whether the presence and severity of allodynia could predict the long-term effect of OBT-A and whether improving allodynia could contribute to the clinical effectiveness of OBT-A. This investigation was conducted on 99 CM patients treated for 1 year and 44 patients treated with periodic OBT-A 155–195 U injections for 2 years. Findings suggested that OBT-A appears to have an impact on central sensitization, expressed by allodynia. By modulating nociceptive transmission and reducing the global migraine burden, this action could be exerted. Patients with more severe allodynia have a limited long-term effect on the frequency of headache. Modulation of central sensitization, despite the persistence of frequent headache, could reduce migraine disability.