Diffusion tensor imaging in cocaine dependence: Regional effects of cocaine on corpus callosum and effect of cocaine administration route

Recent studies demonstrated that diffusion tensor imaging (DTI) can provide information regarding white matter integrity of the corpus callosum (CC). In this study, DTI parameters were compared between cocaine dependent subjects (CDs) and non-drug using controls (NCs) in midsagittal CC. DTI images were acquired from 19 CDs and 18 age-matched NCs. The midsagittal CC was segmented into: genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. Linear mixed models analyses showed that, relative to NCs, CDs had lower fractional anisotropy (FA), higher radial diffusivity (λ⊥), and higher mean diffusivity (Dav) in the isthmus; higher λ⊥ and Dav in the rostral body; and lower FA in the splenium. After including mass of lifetime alcohol use in the mixed model analysis of covariance (ANCOVA) as a covariate, significant between group differences in λ⊥ in the rostral body and isthmus remained. These results suggest that alterations in λ⊥ in the rostral body and isthmus were mainly due to cocaine use, consistent with previous studies showing that cocaine may alter myelin integrity. Between group differences in FA in the isthmus and splenium, and Dav in the rostral body and isthmus became non-significant after inclusion of alcohol use as a covariate. This is suggestive of alcohol influencing these values, or may be related to the decreased degrees of freedom for these effects. Consistent with clinical data of greater severity of drug use in smoked versus intranasal cocaine, subjects who smoked cocaine showed lower FA and higher λ⊥ compared to intranasal CDs.