White matter impairment in heroin addicts undergoing methadone maintenance treatment and prolonged abstinence: a preliminary DTI study

Methadone maintenance treatment (MMT) might cause the impairments of neuropsychological and neurotransmitter function in opioid addicts. Whether long-term MMT could lead to the impairment of white matter (WM) in heroin addiction brain is unclear. This study compared the WM integrity in the bilateral frontal lobe, temporal lobe, splenium and genu of corpus collasum (CC) between MMT patients (n=13), former heroin addicts (n=11) in prolonged abstinence (PA), and healthy control subjects (n=15) using diffusion tensor imaging (DTI). Fractional anisotropy (FA), apparent diffusion coefficient (ADC) and eigenvalues (λ(⊥), λ(||)) were measured. The correlation between DTI measures and accumulated former heroin dose, total methadone consumption, and PA duration were determined. Although the PA subjects showed no difference in DTI measures relative to the controls, the extensive correlations between the former heroin consumption and the DTI measures were noted. The MMT subjects showed a decreased FA values in the left genu, as well as the increased ADC and λ(⊥) values in the left splenium of CC in comparison to the controls. Compared with the PA, the MMT subjects had a significantly increased ADC value in the bilateral splenium of CC. Importantly, the methadone dosage used in the MMT group was correlated with the FA value in the left splenium of CC and in the right frontal lobe. Our preliminary results suggest that methadone plays a role in the impairment of WM integrity in heroin users on long-term MMT and the normalization of WM injury may occur during abstinence.