Real-World Safety and Tolerability of Low-Intensity Repetitive Transcranial Magnetic Stimulation in Fibromyalgia: A Multicenter Observational Cohort Study

Background/Objectives: Low-intensity repetitive transcranial magnetic stimulation (Li-rTMS) is an emerging non-invasive neuromodulation approach for fibromyalgia; however, large-scale data on safety and tolerability in routine clinical settings remain limited. This study aimed to evaluate the safety and tolerability of Li-rTMS in patients with fibromyalgia treated in outpatient practice. Methods: A retrospective multicentre observational cohort study was conducted using routinely collected clinical data from nine outpatient centres (November 2020–March 2026). Safety analyses included all patients initiating Li-rTMS treatment (intention-to-treat cohort, n = 1381). The protocol consisted of eight stimulation sessions delivered using a CE-certified medical device. Patient-reported tolerability and perceived symptom changes in three predefined domains (headache, generalized pain, and sleep) were assessed using a standardized 0–10 scale and analysed descriptively, with stratification by age group. Results: Li-rTMS was generally well tolerated across all age groups, including those >65 years. High-intensity symptom worsening was infrequent (headache 3.8%, generalized pain 6.1%, sleep disturbances 2.1%), predominantly mild and self-limited. No serious adverse events were spontaneously reported or clinically identified during routine clinical follow-up, within the limitations inherent to a real-world passive registry framework. Exploratory observations from patient-initiated recall sessions did not suggest an increased adverse symptom burden with repeated exposure. Conclusions: Li-rTMS demonstrated a favourable patient-reported tolerability profile among patients with available follow-up data, characterized by a low frequency of transient high-intensity symptom worsening and the absence of serious adverse events spontaneously reported or clinically identified during routine, non-systematic follow-up. These findings support the feasibility of repeated Li-rTMS administration in outpatient settings; however, due to the observational design and non-systematic follow-up, no conclusions regarding clinical efficacy can be drawn.