White matter abnormalities in methcathinone abusers with an extrapyramidal syndrome.

We examined white matter abnormalities in patients with a distinctive extrapyramidal syndrome due to intravenous methcathinone (ephedrone) abuse. We performed diffusion tensor imaging in 10 patients and 15 age-matched controls to assess white matter structure across the whole brain. Diffuse significant decreases in white matter fractional anisotropy, a diffusion tensor imaging metric reflecting microstructural integrity, occurred in patients compared with controls. In addition, we identified two foci of severe white matter abnormality underlying the right ventral premotor cortex and the medial frontal cortex, two cortical regions involved in higher-level executive control of motor function. Paths connecting different cortical regions with the globus pallidus, the nucleus previously shown to be abnormal on structural imaging in these patients, were generated using probabilistic tractography. The fractional anisotropy within all these tracts was lower in the patient group than in controls. Finally, we tested for a relationship between white matter integrity and clinical outcome. We identified a region within the left corticospinal tract in which lower fractional anisotropy was associated with greater functional deficit, but this region did not show reduced fractional anisotropy in the overall patient group compared to controls. These patients have widespread white matter damage with greatest severity of damage underlying executive motor areas.