Dynamic Changes in Interictal Burden During 3-Year Follow-Up for Medication Overuse Headache

Purpose: Treatment improves medication overuse headache (MOH), but interictal burden may persist. Limited longitudinal data leave uncertainty about whether residual burden reflects persistent impairment, recovery, or newly emerging burden. We investigated changes in interictal burden during the 3 years after MOH diagnosis.Methods: This single-center substudy of a nationwide prospective MOH registry enrolled 149 patients at baseline and assessed interictal burden at the 2- and 3-year follow-ups using the 4-item Migraine Interictal Burden Scale (MIBS-4). The Wilcoxon signed-rank test and exact McNemar test were used to analyze paired changes.Results: At 3 years, clinical follow-up was completed by 89 patients and the MIBS-4 by 61; 57 had paired assessments at 2 and 3 years. At this follow-up, 9 of 89 patients (10.1%) had medication overuse (MO). Among patients with paired MIBS-4 assessments, the median score decreased from 2.0 (0.0–4.0) at 2 years to 1.0 (0.0–3.0) at 3 years (p=0.006), and the proportion with substantial-to-severe interictal burden decreased from 47.4% to 29.8% (p=0.031). Recurrence by 3 years affected 8.3% of patients whose MO had resolved at 2 years. At 3 years, substantial-to-severe interictal burden persisted in 28.6% of patients whose MO had resolved.Conclusion: Interictal burden improved between 2 and 3 years after MOH diagnosis, yet clinically relevant burden persisted in more than one-quarter of patients whose MO had resolved. These findings suggest that recovery from MO and recovery from interictal burden do not necessarily proceed in parallel, supporting the inclusion of interictal burden in long-term MOH assessment.