Differential diagnosis of Parkinson's disease

Genetically Targeted Clinical Trials in Parkinson's Disease: Learning from the Successes Made in Oncology

Clinical trials in neurodegenerative disorders have been associated with high rate of failures, while in oncology, the implementation of precision medicine and focus on genetically defined subtypes of disease and targets for drug development have seen an unprecedented success. With more than 20 genes associated with Parkinson’s disease (PD), most of which are highly penetrant and often cause early onset or atypical signs and symptoms, and an increasing understanding of the associated pathophysiology culminating in dopaminergic neurodegeneration, applying the technologies and designs into the field of neurodegeneration seems a logical step. This review describes some of the methods used in oncology clinical trials and some attempts in Parkinson’s disease and the potential of further implementing genetics, biomarkers and smart clinical trial designs in this disease area.

Genetic predispositions of Parkinson's disease revealed in patient-derived brain cells

Parkinson's disease (PD) is the second most prevalent neurological disorder and has been the focus of intense investigations to understand its etiology and progression, but it still lacks a cure. Modeling diseases of the central nervous system in vitro with human induced pluripotent stem cells (hiPSC) is still in its infancy but has the potential to expedite the discovery and validation of new treatments. Here, we discuss the interplay between genetic predispositions and midbrain neuronal impairments in people living with PD. We first summarize the prevalence of causal Parkinson's genes and risk factors reported in 74 epidemiological and genomic studies. We then present a meta-analysis of 385 hiPSC-derived neuronal lines from 67 recent independent original research articles, which point towards specific impairments in neurons from Parkinson's patients, within the context of genetic predispositions. Despite the heterogeneous nature of the disease, current iPSC models reveal converging molecular pathways underlying neurodegeneration in a range of familial and sporadic forms of Parkinson's disease. Altogether, consolidating our understanding of robust cellular phenotypes across genetic cohorts of Parkinson's patients may guide future personalized drug screens in preclinical research.

Low clinical diagnostic accuracy of early vs advanced Parkinson disease: clinicopathologic study

OBJECTIVES

Determine diagnostic accuracy of a clinical diagnosis of Parkinson disease (PD) using neuropathologic diagnosis as the gold standard.

METHODS

Data from the Arizona Study of Aging and Neurodegenerative Disorders were used to determine the predictive value of a clinical PD diagnosis, using 2 clinical diagnostic confidence levels, PossPD (never treated or not clearly responsive) and ProbPD (responsive to medications). Neuropathologic diagnosis was the gold standard.

RESULTS

Based on first visit, 9 of 34 (26%) PossPD cases had neuropathologically confirmed PD while 80 of 97 (82%) ProbPD cases had confirmed PD. PD was confirmed in 8 of 15 (53%) ProbPD cases with <5 years of disease duration and 72 of 82 (88%) with ≥5 years of disease duration. Using final diagnosis at time of death, 91 of 107 (85%) ProbPD cases had confirmed PD. Clinical variables that improved diagnostic accuracy were medication response, motor fluctuations, dyskinesias, and hyposmia.

CONCLUSIONS

Using neuropathologic findings of PD as the gold standard, this study establishes the novel findings of only 26% accuracy for a clinical diagnosis of PD in untreated or not clearly responsive subjects, 53% accuracy in early PD responsive to medication (<5 years' duration), and >85% diagnostic accuracy of longer duration, medication-responsive PD. Caution is needed when interpreting clinical studies of PD, especially studies of early disease that do not have autopsy confirmation. The need for a tissue or other diagnostic biomarker is reinforced.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that a clinical diagnosis of PD identifies patients who will have pathologically confirmed PD with a sensitivity of 88% and specificity of 68%.

Spatial distribution of Parkinson's disease mortality in Spain, 1989-1998, as a guide for focused aetiological research or health-care intervention

BACKGROUND

Aetiologically, genetic and environmental factors having an uneven spatial distribution may underlie Parkinson's disease (PD). Undiagnosis of PD in selected regions might have limited access to treatment with levodopa and simultaneously, if present at death, determined PD underreporting at the death record. The purpose of this study was to describe and analyse municipal mortality due to PD in Spain in aetiological and interventional perspective.

METHODS

PD mortality at a municipal level was modelled using the Besag-York- Molliè autoregressive spatial model, combining demographic information with cause-of-death diagnostic data (International Classification of Diseases 9th Revision (ICD-9) code 332.0). Municipal relative risks (RRs) were independently estimated for women, men and both sexes, and plotted on maps depicting smoothed RR estimates and the distribution of the posterior probability of RR>1.

RESULTS

A south-north gradient, with large geographical areas suggesting clustered towns with high mortality, was seen in Asturias, the Basque Country, Balearic Islands and, particularly, in the Lower Ebro valley around Tarragona. Similarly, there was a suggestion that lowest mortality was clustered in the south-east and south-west. We identified some isolated or clustered municipalities with high mortality that were situated near industrial plants reported to be associated with environmental xenobiotic emissions. However, the same pattern was also observed for some cities with low mortality.

CONCLUSION

Municipal PD mortality in Spain was unevenly distributed. Patterns were roughly similar to reported provincial PD mortality and use of levodopa. While the overall pattern appears to result from spatially selective PD undiagnosis, and can not be ascribed to industrial emissions, it can not be excluded that selected "hot spots" reflect genetic factors and/or environmental exposures inducing parkinsonism. A few municipal populations, located in low-mortality-risk areas in the vicinity of polluting plants or registering high excess PD mortality, might constitute a priority for conducting direct etiological studies. Additionally, interventions aimed to reduce potential PD undiagnosis might be most appropriate in the South.

Single-photon emission computed tomography and positron emission tomography evaluations of patients with central motor disorders

Neuroimaging biomarkers in movement disorders during the past decade have served as diagnostic agents (Europe), tools for evaluation of novel therapeutics, and a powerful means for describing pathophysiology by revealing in vivo changes at different stages of disease and within the course of an individual patient's illness. As imaging with agents tracking dopaminergic function become more available, the next decade promises to enhance our clinical sophistication in the optimal use of dopaminergic imaging biomarkers for differential diagnosis, characterization of at-risk populations, guiding selection and management of appropriate treatments. The clinical role of these agents as clinical tools goes hand in hand with the development and availability of disease-modifying drugs, which carry the additional requirement for early and accurate diagnosis and improved clinical monitoring once treatment is initiated. Challenges remain in the ideal application of neuroimaging in the clinical algorithms for patient assessment and management. Further, the application of imaging to other targets, both monamineric and nonmonoaminergic, could serve a function beyond the important delineation of pathologic change occurring in patients with Parkinson's disease to suggest some role in improved phenotyping and classification of patients with Parkinson's disease presenting with different symptom clusters. New areas of focus based on the elucidation of mechanisms at the cellular and molecular level, including intense interest in alpha-synuclein and other protein inclusions in neurons and glia, have piqued interest in their in vivo assessment using scinitigraphic methods. Perhaps ultimately, treatment that is targeted to a better delineated pathophysiology-based characterization of movement disorder patients will emerge. The application of neuroimaging biomarkers to multiple ends in movement disorders provides an important model for the multiple roles diagnostic imaging agents can serve in neurodegenerative disorders; for diagnosis, for elaborating pathophysiology in patient populations, for developing new drugs, ultimately for improving clinical management.

Extrapontine myelinolysis presenting as acute parkinsonism

BACKGROUND

Extrapontine myelinolysis presenting with extra pyramidal features suggestive of parkinsonism may be a challenging clinical syndrome. Clinicians should maintain their vigilance while correcting electrolyte imbalances, especially with associated co-morbidity.

CASE PRESENTATION

A 41-year-old woman presented with acute parkinsonism like features while on a holiday. This followed slow correction of hyponatraemia after repeated vomiting. MRI changes were suggestive of Extrapontine myelinolysis(EPM). This case is at variance with four previous cases reported in the medical literature in that the patient made a full clinical recovery and the MR changes resolved with symptomatic support alone.

CONCLUSION

Extrapontine myelinolysis could make a complete recovery with symptomatic support alone. During hyponatraemia correction, rapid osmotic shifts of fluid that cause hypernatremia, causes myelinolysis rather than absolute serum sodium level. Even gradual correction of hyponatraemia can produce myelinolysis, especially with pre-existing malnourishment, alcoholism, drug misuse, Addison's disease and immuno-suppression. Pallidial sparing is typical of EPM in MRI scans.

Pesticides and Parkinson's disease--is there a link?

Parkinson's disease (PD) is an idiopathic disease of the nervous system characterized by progressive tremor, bradykinesia, rigidity, and postural instability. It has been postulated that exogenous toxicants, including pesticides, might be involved in the etiology of PD. In this article we present a comprehensive review of the published epidemiologic and toxicologic literature and critically evaluate whether a relationship exists between pesticide exposure and PD. From the epidemiologic literature, there does appear to be a relatively consistent relationship between pesticide exposure and PD. This relationship appears strongest for exposure to herbicides and insecticides, and after long durations of exposure. Toxicologic data suggest that paraquat and rotenone may have neurotoxic actions that potentially play a role in the development of PD, with limited data for other pesticides. However, both the epidemiology and toxicology studies were limited by methodologic weaknesses. Particular issues of current and future interest include multiple exposures (both pesticides and other exogenous toxicants), developmental exposures, and gene-environment interactions. At present, the weight of evidence is sufficient to conclude that a generic association between pesticide exposure and PD exists but is insufficient for concluding that this is a causal relationship or that such a relationship exists for any particular pesticide compound or combined pesticide and other exogenous toxicant exposure.

A comparative study of age-related brain pathology--are neurodegenerative diseases present in nonhuman animals ?

Although some aged dogs definitely have dementia-like conditions, they have rather different brain histopathology from that seen in Alzheimer's disease including the shape of senile plaques, severity of neuron loss and absence of neurofibrillary tangles. Aged wild-type mice never show such brain lesions at all. In addition, no cases of Parkinson's disease have been reported in nonhuman animals yet. The reason for this might be non-parallel aging of the whole body and brain. If such nonhuman animals had a longer life span, like humans, typical Alzheimer's and Parkinson's lesions would be formed in the brain. As the rate of deposition of the misfolded proteins causing the lesions might be slow, nonhuman animals normally die before the lesions appear.

Does this patient have Parkinson disease?

CONTEXT

Diagnosis of Parkinson disease (PD) remains challenging. An accurate diagnosis is important because effective symptomatic treatment for PD is available.

OBJECTIVE

To systematically review the literature for information on the precision and accuracy of the clinical examination for diagnosing PD.

DATA SOURCES

MEDLINE database was searched for all English-language articles related to the diagnosis of PD published from January 1966 through April 2001. The reference lists of all articles retrieved were searched for additional relevant sources.

STUDY SELECTION

Studies in which patients presented with 1 or more typical features of PD were included if the final diagnosis was confirmed by a suitable criterion standard and data could be extracted to determine the accuracy of 1 or more symptoms or signs. Variability in descriptions of symptoms and signs made it impossible to combine data across existing studies for most findings.

DATA SYNTHESIS

We identified 6 studies that met our criteria. The positive (presence) likelihood ratios (LRs) for tremor as a symptom of PD ranged from 1.3 to 17 (range of negative [absence] LRs, 0.24 to 0.60). Tremor as a sign of PD produced a range of positive LRs from 1.3 to 1.5 (negative LRs, 0.47 to 0.61). Clinical features useful in the diagnosis of PD include a history of the combination of symptoms of rigidity and bradykinesia (positive LR, 4.5; negative LR, 0.12); a history of loss of balance (range of positive LRs, 1.6 to 6.6; range of negative LRs, 0.29 to 0.35), symptoms of micrographia (range of positive LRs, 2.8 to 5.9; range of negative LRs, 0.30 to 0.44), and a history of shuffling gait (range of positive LRs, 3.3 to 15; range of negative LRs, 0.32 to 0.50). Trouble with certain tasks such as turning in bed (positive LR, 13; negative LR, 0.56), opening jars (positive LR, 6.1; negative LR, 0.26), and rising from a chair (range of positive LRs, 1.9 to 5.2; range of negative LRs, 0.39 to 0.58). Useful signs include the glabella tap test (positive LR, 4.5; negative LR, 0.13), difficulty walking heel-to-toe (positive LR, 2.9; negative LR, 0.32), and rigidity (range of positive LRs, 0.53 to 2.8; range of negative LRs, 0.38 to 1.6). Significant selection bias was detected in all studies included for review.

CONCLUSIONS

Symptoms of tremor, rigidity, bradykinesia, micrographia, shuffling gait, and difficulty with the tasks of turning in bed, opening jars, and rising from a chair should be carefully reviewed in all patients with suspected PD. The glabella tap and heel-to-toe tests also should be assessed.

[Wilson's disease. Clinical presentation, treatment and evolution in 21 cases]

PURPOSE

Wilson's disease is characterized by neuropsychiatric symptoms with frequent extrapyramidal and intellectual presentations. They have an insidious evolution that leads to a late diagnosis and less therapeutic effectiveness in the advanced forms.

METHODS

We report 21 cases of Wilson's disease with neurological complications, emphasizing clinical semiology, diagnostic means and problems of the therapeutics in our country.

RESULTS

The average age at the beginning of the disease was 17.6 years, with a female prevalence (8/13). The signs at first were mostly all neurological (71.4%), then psychiatric (19%) or hepatic (19%). The most common neurological signs were dystonia of members (81%), dysarthria (76%), tremors (76%) or disorders of motoricity (71.4%). Sometimes there were sialorrhea or disorders of the handwriting. The Kayser-Fleischer ring was present in 19 patients. Eighteen patients had clinical and/or biological hepatic involvement. The diagnosis was confirmed by biochemical examinations, which found a low rate of copper in blood, a sinking rate of ceruloplasmin and a very high rate of urinary copper. The cerebral computer tomography shows a cortical and/or subcortical atrophy (37%), and/or a low density of the central grey cores (35%). The treatment was based on D-penicillamine and/or zinc sulfate, according to the availability of the drugs. The evolution was favourable among 18 patients (85%) and not good in 42.8% of the cases. Six of the first patients had poor evolution after many years of follow-up. Finally, only 12 patients (57%) had a very good outcome. The family investigation made among 17 patients revealed 13 family cases. The only predictive factor of a poor evolution was the therapeutic noncompliance (P = 0.006).

CONCLUSIONS

The neurological presentations are traditional during the Wilson's disease, but are often ignored. We must suspect the disease in children when faced with disorders of handwriting or school failures and in the adult, when faced with neurological symptoms in a patient having a hepatic disease. We must not hesitate to consider it even given purely psychiatric signs, and we had better know to seek the neurological ones.