PET AND SPECT STUDIES IN PARKINSONS-DISEASE

Positron emission tomography (PET) and single photon emission tomograp hy (SPECT) provide sensitive means for quantifying the loss of nigrost riatal dopaminergic fibres in Parkinson's disease and for detecting th e presence of dopaminergic dysfunction in asymptomatic at-risk relativ es and patients with isolated tremor. Functional imaging can also be u sed to follow the rate of disease progression objectively, determine t he efficacy of putative neuroprotective agents, and monitor the viabil ity of transplants of fetal tissue. Additionally, in vivo pharmacologi cal changes associated with development of treatment complications (fl uctuations, dyskinesias) can be studied. Loss of dopaminergic projecti ons produces profound changes in resting and activated brain metabolis m. PET and SPECT activation studies have suggested that the akinesia o f Parkinson's disease is associated with failure to activate the suppl ementary motor and dorsal pre-frontal areas. Activation of these corti cal areas is restored towards normal by the use of dopaminergic medica tion, striatal transplantation with fetal mesencephalic tissue, and pa llidotomy. The aim of this chapter is to review the insight which func tional imaging has given us into the pathophysiology of parkinsonism.