We retrospectively analysed routine clinical data of EM and CM patients presented at the West German Headache Center, Department of Neurology, University Hospital Essen, Germany between November 2018 and December 2019. The analysis was approved by the independent ethics committee of the University Hospital Essen. Patients meeting the following criteria were included in the analysis: a) EM/CM patients with at least 4 migraine days a month according to the current diagnostic criteria of the International headache classification (ICHD-3 [
8]), b) documented history of the last 90 days prior starting erenumab therapy regarding monthly migraine days (MMD), monthly headache days (MHD) and monthly intake of acute medication (AMD), c) completion of a 90 days treatment interval with monthly 70 mg erenumab d) available complete clinical data including headache diaries and side effects. A paper-based headache diary was used. MMD, MHD and AMD are the average monthly mean values over the respective total observation period of 90 days. A headache day was defined as a day with any kind of headache, a migraine day was defined by patients when they had severe pain, migraine pain characteristics (pulsating, one-sided pain), aura symptoms, vegetative symptoms like phono- or photophobia, nausea, vomiting, need for rest, or when triptans were taken. Most patients answered questionnaires regarding different aspects of migraine: intensity of migraine (
n = 95), duration of the migraine attack (
n = 90), effect of acute therapy (
n = 90), effect on the aura (
n = 90), need for rest (
n = 93), dizziness (
n = 92), nausea (
n = 93), phono- and photophobia (
n = 93) as well as therapy satisfaction (
n = 93). Due to reasons of reimbursement by the German statutory health insurance, all treated patients had tried at least 5 (when EM) and 6 (when CM) approved prophylactic drugs previously without sufficient treatment effects, had discontinued those due to side effects, or were not eligible for intake due to contraindication. Approved drug classes were the following: betablockers (metoprolol or propranolol), tricyclic antidepressants (amitriptyline), calcium channel blockers (flunarizine), anticonvulsants (topiramate and valproic acid) and for CM additionally onabotulinumtoxin A. The pre-existing medication taken for other indications or migraine prophylaxis were not changed and on a stable dosage at least 6 weeks prior to treatment start. No other medication with a potential disease modifying effect was started during the observational period. Data were analysed using SPSS software (IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp). Wilcoxon’s test was used to compare MMD, MHD, and AMD before and after treatment. The test procedure was two-sided, Bonferoni’s method for multiple comparisons was set at
p < 0.05/3 = 0.016. Patient reported outcomes were analysed descriptively.