SLC6A3 and Parkinson disease: CNS involvement in metabolic disorders such as mitochondrial disease is often thought to be bilateral and symmetric, with generalized brain or cerebellar atrophy, widespread white matter changes, or bilateral, symmetric basal ganglia lesions.2,47 Even lateralized parkinsonism symptoms are not necessarily accompanied by asymmetric lesions on brain MRI or dopamine transport (DAT-SPECT) imaging.29 Interestingly, many of our patients had large regions of asymmetric binding abnormalities, with otherwise normal or symmetric MRI.