Hyperbaric oxygen therapy improves clinical symptoms and functional capacity and modulates thalamic connectivity in ME/CFS: a prospective cohort study

Background Hyperbaric oxygen therapy (HBOT) has been proposed as a treatment for myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), but evidence remains limited. This study evaluated its clinical effectiveness and feasibility, as well as associated functional brain changes. Methods Thirty patients with ME/CFS (mean age 42.3 ± 11.7 years; 7 males, 23 females) received 40 HBOT sessions. Clinical outcomes were assessed at baseline, during treatment, and four weeks post-treatment. The primary outcome was change in the physical functioning subscale of the Short Form-36 Health Survey (SF-36 PF). Secondary outcomes included severity of core symptoms assessed via questionnaires, exercise capacity, handgrip strength, cognitive performance, orthostatic intolerance, and brain magnetic resonance imaging (MRI; volumetry and functional connectivity [FC]). Thirty age- and sex-matched healthy controls (mean age 42.3 ± 11.3 years; 7 males, 23 females) were included for MRI comparison. Results SF-36 PF significantly improved during HBOT compared with baseline (g = 0.71, p = 0.006). SF-36 pain ( p = 0.002, g = 0.79) and Chalder Fatigue Scale also showed clinically meaningful reductions ( p < 0.001, g = −0.87). Exercise capacity (g = 0.66), muscle strength (g = 0.40), and information processing speed (g = 0.52) improved significantly after treatment (all p < 0.05). Treatment adherence was high and tolerability was favorable, with no major adverse events reported. Functional MRI analyses revealed increased thalamic FC in ME/CFS patients compared to healthy controls in bilateral sensorimotor ( p < 0.001, t = 5.65, FDR-corrected) and visuo-occipital regions ( p < 0.001, t = 5.40, FDR-corrected) at baseline. Following HBOT, thalamic hyperconnectivity shifted toward patterns observed in healthy controls. Responders, defined as a ≥ 10 points increase in SF-36 PF, showed greater reductions in thalamic hyperconnectivity than non-responders ( p < 0.001, t = −4.34 to −5.18, FDR-corrected). Conclusions HBOT was well tolerated and associated with significant improvements in physical functioning, fatigue, pain, and cognitive performance in ME/CFS. The post-treatment shift in thalamocortical connectivity toward healthy control patterns and its association with clinical response support the hypothesis that functional thalamic dysregulation contributes to ME/CFS pathophysiology and may be modulated by HBOT. This provides a network-level rationale for controlled trials to confirm therapeutic efficacy. Trial registration ClinicalTrials.gov NCT06118138. Registered 01 November 2023 – Retrospectively registered, https://clinicaltrials.gov/study/NCT06118138?cond=ME%2FCFSamp;term=HBOTamp;rank=1 .