Role of dopaminergic neurotransmission in pathophysiology of action tremor in Parkinson's disease

Rest tremor (RT), a tremor that occurs in a body part that is completely supported against gravity, is together with rigidity and bradykinesia among the core features of Parkinson's disease (PD). In addition to classical RT, many PD patients also have action tremor (AT) occurring during sustained postures or voluntary movement. Earlier studies showed a good correlation between striatal dopamine transporter (DAT) binding, measured with [(123)I] FP-CIT SPET and bradykinesia. By contrast, neither rigidity nor rest tremor seems to be closely related to the degree of dopaminergic denervation as measured by DAT imaging. Little is known about the relationship, if any, between the severity of action tremor and striatal DAT binding.