Buprenorphine and Surface-based Brain Morphometry: Impacts on Cortical Thickness, Depth, and Gyrification in Patients with Opioid Use Disorder.

Background: Opioid use disorder (OUD) is associated with structural brain alterations. Buprenorphine maintenance treatment (BMT)'s impact on brain morphology remains underexplored. We examined the effect of BMT on surface-based morphometry (SBM) metrics- cortical thickness, sulcal depth, gyrification, and fractal dimension, in a longitudinal controlled design. Methods: Twenty-five men with OUD and age- and education-matched participants in the control group were recruited. Participants underwent T1-weighted MRI scans immediately after starting BMT and after six months of treatment. SBM metrics were analyzed using the Computational Anatomy Toolbox 12 (CAT12), employing threshold-free cluster enhancement (TFCE) and family-wise error correction. Results: At baseline, individuals with OUD had greater cortical thickness in superior parietal and occipital regions and reduced thickness in the inferior temporal gyrus versus participants in the control group. After six months, significant cortical thickness reductions were observed in the occipital pole, cuneus, and occipito-temporal gyri, and calcarine sulcus in both hemispheres; sulcal depth, gyrification, and fractal dimension remained unchanged. We observed negative correlations between buprenorphine dosage and change in cortical depth in the parahippocampal region (r = -0.53, p = .007) and temporal pole (r = -0.55, p = .005), and positive correlations with fractal dimension in the medial orbitofrontal cortex (r = 0.53, p = .006) and gyrification in the lateral orbital region (r = 0.56, p = .004). Conclusion: BMT is associated with a generalized cortical thinning in sensory regions, while dose-dependent changes are observed in memory, emotional regulation, and cognitive control regions, highlighting neuroadaptive processes in overall treatment and medication-specific effects.