Fig. 3From: Cervical non-invasive vagus nerve stimulation (nVNS) for preventive and acute treatment of episodic and chronic migraine and migraine-associated sleep disturbance: preliminary findings from a prospective observational cohort studyNumber of headache days per month (mean ± SEM). Abbreviations: CM chronic migraine, EM episodic migraine, nVNS non-invasive vagus nerve stimulation, SEM standard error of the mean. Number of headache days per month at baseline (blue bars) and after 3 months of treatment with nVNS (orange bars) in all patients, patients with EM, and patients with CM. Baseline measures were determined on the basis of patient reporting and medical history. Data are shown as mean ± SEMBack to article page