Residual striatal dopaminergic nerve terminals in very long-standing Parkinson's disease: a single photon emission computed tomography imaging study.

Molecular imaging studies of Parkinson's disease (PD) progression mostly focus on the first 5 years after disease onset, demonstrating rapid initial nigrostriatal neuronal loss. The fate of residual functional dopaminergic nerve terminals in patients with long-standing PD has not yet been specifically explored. Therefore, we performed [(123)I]-FP-CIT single photon emission computed tomography (SPECT) in 15 patients with very long-standing PD (mean disease duration 20.6 ± 6.3 years). Measurable uptake of [(123)I]-FP-CIT was still detected in the striata of all patients. As seen in early stages, reduction of tracer uptake in the putamen was more prominent than in the caudate nucleus. Asymmetry in tracer uptake between the two putamen and caudate nuclei was preserved. These findings indicate that degeneration of dopaminergic neurons in PD is not total even after many years of illness. Data should be considered in exploring underlying causes of progressive loss of nigrostriatal dopaminergic neurons and development of future novel dopaminergic therapeutic strategies in PD.