AUTHOR=Guerzoni Simona , Pellesi Lanfranco , Baraldi Carlo , Cainazzo Michela Maria , Negro Andrea , Martelletti Paolo , Pini Luigi Alberto TITLE=Addendum: Long-term Treatment Benefits and Prolonged Efficacy of OnabotulinumtoxinA in Patients Affected by Chronic Migraine and Medication Overuse Headache over 3 Years of Therapy JOURNAL=Frontiers in Neurology VOLUME=9 YEAR=2018 URL=https://www.frontiersin.org/journals/neurology/articles/10.3389/fneur.2018.00641 DOI=10.3389/fneur.2018.00641 ISSN=1664-2295