CHAT and movement disorder: The PPN has also been shown to exhibit reduced levels of choline acetyltransferase in PSP, further implicating it in the pathology of the disease.21 A brief report of a patient with bilateral PPN infarcts and subsequent gait freezing further supports the role of the PPN in locomotion and potential contribution to falls in movement disorders.22 As such, there is clinical and radiological evidence linking gait dysfunction in PSP to the PPN.