In Guadeloupe, there is an abnormally high frequency of atypical
parkinsonism. Only one-third of the patients that develop parkinsonian symptoms were reported to present the classical features of
idiopathic Parkinson disease and one-third a syndrome resembling
progressive supranuclear palsy (PSP). The others were unclassifiable, according to established criteria. We carried out a cross-sectional study of 160 parkinsonian patients to: (i) define more precisely the clinical phenotypes of the PSP-like syndrome and the
parkinsonism that was considered unclassifiable in comparison with previously known disorders; (ii) define the neuropsychological and brain imaging features of these patients; (iii) evaluate to what extent a candidate aetiological factor, the mitochondrial complex I inhibitor
annonacin contained in the fruit and leaves of the tropical plant Annona muricata (soursop) plays a role in the neurological syndrome. Neuropsychological tests and MRI were used to classify the patients into those with
Parkinson's disease (31%), Guadeloupean PSP-like syndrome (32%), Guadeloupean
parkinsonism-
dementia complex (PDC, 31%) and other
parkinsonism-related disorders (6%). Patients with a PSP-like syndrome developed
levodopa-resistant
parkinsonism, associated with early postural instability and supranuclear oculomotor dysfunction. They differed, however, from classical PSP patients by the frequency of
tremor (>50%),
dysautonomia (50%) and the occurrence of
hallucinations (59%). PDC patients had
levodopa-resistant
parkinsonism associated with frontosubcortical
dementia, 52% of these patients had
hallucinations, but, importantly, none had oculomotor dysfunction. The pattern of neuropsychological deficits was similar in both subgroups. Cerebral
atrophy was seen in the majority of the PSP-like and PDC patients, with enlargement of the third ventricle and marked T2-hypointensity in the basal ganglia, particularly the substantia nigra. Consumption of soursop was significantly greater in both PSP-like and PDC patients than in controls and
Parkinson's disease patients. In conclusion, atypical Guadeloupean
parkinsonism comprises two forms of
parkinsonism and
dementia that differ clinically by the presence of oculomotor signs, but have similar cognitive profiles and neuroimaging features, suggesting that they may constitute a single disease entity, and both were similarly exposed to annonaceous
neurotoxins, notably
annonacin.