Abstract
Methadone maintenance treatment (MMT) can induce impairments in brain function and structure, despite its clinical effectiveness. However, the effect of chronic MMT on brain white matter (WM) is not fully known. Thirty-three MMT patients underwent diffusion tensor imaging (DTI) twice – at the start of the study (Scan1) and one year later (Scan2). Tract-based spatial statistics were used to investigate changes in fractional anisotropy (FA), axial diffusivity (AD) and radial diffusivity (RD) between the two scans. The correlations between DTI indices and methadone consumption and neuropsychological status were analysed. We found significantly decreased FA, decreased AD and increased RD in Scan2 in extensive WM regions; overlapping regions were found in the left posterior limb and the retrolenticular part of internal capsule, superior and posterior corona radiata, bilateral external capsule and the right superior longitudinal fasciculus. In addition, the change of FA in the overlapping regions was positively correlated with the accumulated dosage of methadone use, the RD value in Scan2 and non-planning impulsiveness (NPI) measured at follow-up. The results suggest that methadone has damaging effects on WM integrity. The dose-dependent pattern and characteristics of the impairment may suggest new strategies for MMT.
Highlights
Methadone maintenance treatment (MMT) can induce impairments in brain function and structure, despite its clinical effectiveness
The changes in the diffusion tensor imaging (DTI) indices were not significantly correlated with changes in the neuropsychological scores, we found that the mean radial diffusivity (RD) values in the overlapping regions in Scan[2] were positively correlated with non-planning impulsiveness (NPI) scores measured at the one year follow-up (r = 0.37, P = 0.032) (Fig. 3b)
The results of this study indicate that methadone-treated patients have decreased fractional anisotropy (FA), decreased axial diffusivity (AD) and increased RD in extensive white matter (WM) regions
Summary
Methadone maintenance treatment (MMT) can induce impairments in brain function and structure, despite its clinical effectiveness. Emerging evidence suggests that long-term methadone use may lead to adverse consequences for brain structure, metabolism and function and the neuropsychological status of heroin addicted patients. Toxic effects on neuromechanisms due to long-term opioid consumption have been demonstrated, which indicate that opioids may alter brain structure and function by regulating the genesis of neurons, glia and their precursors in the central nervous system, or by disrupting gliogenesis[3]. Previous research measuring cognitive function has demonstrated several negative effects of long-term MMT. We observed a decrease in WM integrity induced by methadone in the splenium of the corpus callosum, and a negative correlation between WM integrity and the accumulated dosage of methadone consumed, by applying diffusion tensor imaging (DTI) with the regions of interest (ROI-wise) method[11]. The former study used a group comparison design, in which the effect of previous heroin use could not be eliminated, and did not use quantitative methods to measure WM integrity
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