Parkinsonism as late sequela of organophosphate intoxication

Risk of Parkinson disease after organophosphate or carbamate poisoning

AIMS

Parkinson disease (PD) is a common neurodegenerative disease. The aim of this study was to evaluate the risk of PD in patients with organophosphate (OP) or carbamate (CM) poisoning by using the Taiwan National Health Insurance Research Database.

METHODS

We conducted a retrospective study involving a cohort of 45 594 patients (9128 patients with a history of OP or CM poisoning and 36 466 control patients) who were selected from the Taiwan National Health Insurance Research Database. The patients were observed for a maximum of 12 years to determine the rates of new-onset PD, and a Poisson regression model was used to identify the predictors of PD. The cumulative incidence of PD between the two cohorts was plotted through Kaplan-Meier analysis.

RESULTS

During the study period, the incidence rate ratio (IRR) of PD in the OP or CM poisoning patients was 1.36-fold [95% confidence interval (CI)=1.26-1.47] higher than that in the control patients in the multivariable model. The absolute incidence of PD was the highest for the group aged ≥75 years in both cohorts (77.4 vs 43.7 per 10 000 person-years). However, the age-specific relative risk was higher for the group aged <50 years (adjusted IRR=3.88; 95% CI=3.44-4.39).

CONCLUSION

Our results suggest that the likelihood of developing PD is greater in patients with OP or CM poisoning than in those without poisoning. OP or CM poisoning may be an independent risk factor for PD.

Acute exposure to chlorpyrifos caused NADPH oxidase mediated oxidative stress and neurotoxicity in a striatal cell model of Huntington's disease

We hypothesized that expression of mutant Huntingtin (HTT) would modulate the neurotoxicity of the commonly used organophosphate insecticide, chlorpyrifos (CPF), revealing cellular mechanisms underlying neurodegeneration. Using a mouse striatal cell model of HD, we report that mutant HD cells are more susceptible to CPF-induced cytotoxicity as compared to wild-type. This CPF-induced cytotoxicity caused increased production of reactive oxygen species, reduced glutathione levels, decreased superoxide dismutase activity, and increased malondialdehyde levels in mutant HD cells relative to wild-type. Furthermore, we show that co-treatment with antioxidant agents attenuated the CPF-induced ROS levels and cytotoxicity. Co-treatment with a NADPH oxidase (NOX) inhibitor, apocynin, also attenuated the CPF-induced ROS production and neurotoxicity. CPF caused increased NOX activity in mutant HD lines that was ameliorated following co-treatment with apocynin. Finally, CPF-induced neurotoxicity significantly increased the protein expression of nuclear factor erythroid 2-related factor (Nrf2) in mutant HD cells as compared to wild-type. This study is the first report of CPF-induced toxicity in HD pathophysiology and suggests that mutant HTT and CPF exhibit a disease-toxicant interaction wherein expression of mutant HTT enhances CPF-induced neurotoxicity via a NOX-mediated oxidative stress mechanism to cause neuronal loss in the full length HTT expressing striatal cells.

Neurological Disorders Associated with Striatal Lesions: Classification and Diagnostic Approach

Neostriatal abnormalities can be observed in a very large number of neurological conditions clinically dominated by the presence of movement disorders. The neuroradiological picture in some cases has been described as "bilateral striatal necrosis" (BSN). BSN represents a condition histo-pathologically defined by the involvement of the neostriata and characterized by initial swelling of putamina and caudates followed by degeneration and cellular necrosis. After the first description in 1975, numerous acquired and hereditary conditions have been associated with the presence of BSN. At the same time, a large number of disorders involving neostriata have been described as BSN, in some cases irrespective of the presence of signs of cavitation on MRI. As a consequence, the etiological spectrum and the nosographic boundaries of the syndrome have progressively become less clear. In this study, we review the clinical and radiological features of the conditions associated with MRI evidence of bilateral striatal lesions. Based on MRI findings, we have distinguished two groups of disorders: BSN and other neostriatal lesions (SL). This distinction is extremely helpful in narrowing the differential diagnosis to a small group of known conditions. The clinical picture and complementary exams will finally lead to the diagnosis. We provide an update on the etiological spectrum of BSN and propose a diagnostic flowchart for clinicians.

Neurosyphilis presenting as parkinsonism

In the postantibiotic era, neurosyphilis continues to have a significant incidence, especially in certain subpopulations. We report, for the first time, neurosyphilis presenting as parkinsonism without more typical neurosyphilitic clinical features. A 53-year-old man developed clinical features of gradual onset consistent with idiopathic Parkinson's disease but was found to have positive treponemal serology and cerebrospinal fluid Venereal Disease Research Laboratory (VRDL) reaction. Antibiotic treatment dramatically improved all the parkinsonian symptoms. However, over the subsequent 15 years, the patient slowly deteriorated again in a manner typical of idiopathic Parkinson's disease. A dopaminergic deficit was demonstrated on ((123)I)FP-CIT SPECT. This is the first report in the postantibiotic era of neurosyphilis presenting as relatively pure parkinsonism. Blood test screening for syphilis is therefore appropriate if there is any clinical doubt about an idiopathic parkinsonian presentation. The patient's late second deterioration may suggest that the neurosyphilitic basal ganglial insult primed or accelerated development of idiopathic-like disease.