White matter plasticity and cognitive improvement in obstructive sleep apnea following CPAP therapy: an automated fiber quantification study.

OBJECTIVE

To employ automated fiber quantification (AFQ) for the longitudinal assessment of segmental white matter microstructure in patients with moderate-to-severe obstructive sleep apnea (OSA) before and after short-term continuous positive airway pressure (CPAP) therapy, and to evaluate associations with clinical metrics.

METHODS

54 untreated male patients with moderate-to-severe OSA and 51 age- and sex-matched healthy controls (HCs) underwent polysomnography, neuropsychological assessment, and diffusion MRI. To evaluate treatment efficacy, 19 OSA patients underwent a follow-up MRI examination after 3 months of CPAP therapy. AFQ was used to extract fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) values at 100 equidistant nodes along 18 major white matter tracts, allowing precise localization of segmental white matter alterations between groups. Subsequently, correlation analyses were performed between the diffusion metrics of the affected tracts and clinical indicators.

RESULTS

At baseline, compared to HCs, point-wise analysis revealed that OSA patients exhibit segmental reductions in MD, AD, and RD values across 9 tracts, alongside elevated AD values in the bilateral cingulum cingulate (CGC). Following 3 months of CPAP, specific segments of the bilateral CGC and the right inferior fronto-occipital fasciculus (IFOF) exhibited increased FA values along with decreased MD and RD values. Conversely, other fiber tracts showed reduced FA values accompanied by elevated MD and RD values. Additionally, baseline AD values in the left CGC correlated with nocturnal oxygen saturation, while post-treatment FA values in the right IFOF correlated with MoCA delayed recall scores.

CONCLUSION

AFQ revealed extensive white matter microstructural alterations in untreated male patients with OSA. Short-term CPAP therapy promoted partial recovery in specific tract segments, which may be associated with cognitive amelioration; nevertheless, specific tract segments continue to exhibit signs of chronic neurological damage. These findings may offer novel evidence supporting focal white matter plasticity as a potential neural mechanism underlying CPAP-related cognitive improvement, thereby providing a theoretical basis for personalized therapeutic strategies.