Two-Year Outcomes and Interictal Burden After Treatment for Medication Overuse Headache.

Background/Objective: Medication overuse headache (MOH) is a disabling secondary headache disorder that arises from an underlying primary headache, most commonly migraine. Although treatment reduces headache frequency and medication overuse, the interictal burden-the impact experienced between headache attacks-remains poorly characterized over the long term. This study evaluated interictal burden and clinical outcomes two years after MOH diagnosis. Methods: This study was derived from a prospective multicenter cohort of patients with MOH, using data from a single center. Of 149 patients enrolled between April 2020 and November 2022, 117 (78.5%) completed the two-year follow-up. Clinical characteristics, medication overuse, monthly headache days, and standardized questionnaires were assessed at baseline and follow-up. Interictal burden was evaluated at two years using the Migraine Interictal Burden Scale (MIBS-4), with scores ≥5 indicating severe burden. Results: At baseline, patients (81.2% female; median age, 45.0 years) reported a median of 16.0 monthly medication days (interquartile range, 13.0-23.0). Medication overuse decreased from 100% at baseline to 24.2% at one year and 17.1% at two years. Among 117 patients with available two-year MIBS-4 data, 25 (21.4%) had severe interictal burden. Compared with those without severe burden, these patients had greater headache-related impact and disability (HIT-6: 68.0 vs. 64.0, p = 0.019; MIDAS: 110.0 vs. 36.0, p = 0.002), higher psychological burden (PHQ-9: 11.0 vs. 8.0, p = 0.032; GAD-7: 7.0 vs. 4.0, p = 0.010), and were more likely to be current smokers (20.0% vs. 4.3%, p = 0.036). Notably, 14.4% of patients with resolved medication overuse still reported severe interictal burden. Conclusions: Two years after MOH diagnosis, severe interictal burden was observed in a substantial proportion of patients and was associated with greater baseline disability and psychological distress. These findings highlight the need for long-term monitoring and management beyond initial medication withdrawal.