Occipital hypoperfusion and motor reserve in Parkinson's disease: an early-phase ¹⁸F-FP-CIT PET study

Individual variability exists in parkinsonian motor symptoms despite a similar degree of nigrostriatal dopamine depletion in Parkinson's disease (PD), called motor reserve. We enrolled 397 patients newly diagnosed with PD who underwent dual-phase ¹⁸F-FP-CIT PET upon initial assessment. Individual motor reserve was estimated based on initial parkinsonian motor symptoms and striatal dopamine transporter availability using a residual model. Patients with low motor reserve (the lowest quartile group, n = 100) exhibited decreased uptake in the occipital region compared to those with high motor reserve (the highest quartile group, n = 100) on early-phase ¹⁸F-FP-CIT PET images. Patients with high motor reserve had a lower risk of conversion to dementia than the those with low motor reserve, whereas the effect of PD groups on the risk of dementia conversion was not mediated by occipital hypoperfusion. These findings suggest that cerebral hypoperfusion in the occipital region is associated with low motor reserve in patients with PD.