TH and neurodegeneration with brain iron accumulation 5: With the pathology seen in the substantia nigra of BPAN patients (Saitsu et al., 2013; Paudel et al., 2015), we evaluated the dopaminergic motor pathways using immunolabeling of Tyrosine Hydroxylase (TH), an enzyme critical for the production of dopamine, allowing us to visualize the dopaminergic neurons of the nigrostriatal tracts.