We previously reported on 131 parkinsonian patients of African-Caribbean and Indian origin attending
movement disorders clinics in six London Hospitals, of whom approximately 20% manifested atypical
parkinsonism with a late-onset, akinetic-rigid predominant syndrome, postural instability and minimal
resting tremor refractory to
levodopa therapy and
dopamine agonists (see Hu et al., Neurology 2000;54[Suppl.3]: A188 and Hu et al., Mov Disord 2000;15[Suppl.3]:S212). To better elucidate the phenotype of these atypical patients (18)FDG/(18)F-
dopa positron emission tomography (PET) were performed in a subgroup to look for cortical and striatal metabolic changes suggestive of
multiple system atrophy (MSA),
progressive supranuclear palsy (PSP),
corticobasal degeneration (CBD), or
dementia with Lewy bodies. Magnetic resonance imaging (MRI) rating of cerebral vascular lesion load, putaminal
atrophy, and neuropsychological testing were also performed. Discriminant function analysis of (18)F-
dopa/(18)FDG striatal metabolism in 43 patients failed to separate atypical ethnic minority from typical Caucasian
Parkinson's disease (PD) patients. Additionally, atypical Indian and African-Caribbean patients did not show cortical reductions in
glucose metabolism suggestive of PSP, CBD, or DLB. Cerebral vascular lesion load rated in these patients did not differ between atypical and typical PD groups, and none of the atypical patients had MRI changes suggestive of MSA or PSP. Our results suggest the atypical parkinsonian phenotype seen in African-Caribbean and Indian patients represents a
levodopa-refractory form of PD separate from MSA or PSP in most patients.