This patient has a Parkinsonian gait manifested by stooped posture, decreased arm swing, and en-bloc turning. Note the asymmetric resting tremor of his hands. Although his stride length is normal, this is common early in the course of the disease or in response to treatment. Parkinsonian gait results from basal ganglia dysfunction. This can be due to either reduced dopaminergic output of the substantia nigra such as occurs in idiopathic Parkinson's disease or blockade of the postsynaptic dopamine receptors in the basal ganglia such as occurs in drug-induced parkinsonism.