Defining premotor Parkinson’s disease: a window of opportunity for neuroprotection?

[Development of early diagnosis of Parkinson's disease and comprehensive economic analysis of the effect of its implementation]

The paper summarizes the literature and author's data on the development of early (preclinical) diagnosis of Parkinson's disease (PD). Implementation of this diagnosis will promote the use of preventive therapy and change investments in diagnosis and treatment of patients. The paper declares that at present the only approach to early diagnosis of PD is positron-emission tomography of the nigrostriatal dopaminergic system, but it cannot be used for preventive examination due to its high cost. The authors consider that a less specific, but more promising approach to the development of early diagnosis of PD is the search for markers in body fluids, mainly in the blood, in patients at the prodromal stage of PD. Indeed, a number of markers as changes in the level of metabolites of monoamines, sphingolipids, urates, and indicators of oxidative stress were found in patients selected for the risk group of the prodromal stage of PD, according to characteristic premotor symptoms. In addition, it is assumed that the search for blood markers at an earlier - pre-prodromal stage is possible only in animal models of PD at the early preclinical stage. This approach can also be used to verify blood markers identified in patients at the clinical stage of PD. It is also evident that the complex socio-economic factors influencing the incidence of PD is different in developed versus developing countries. The societal and medical costs of Parkinson's are huge and efforts to improve early preclinical diagnosis of PD will lead to considerable economical and societal benefits. For instance this will allow efficient selection of patients for preclinical diagnostic tests. To assess the effectiveness of this strategy considering the uncertainty of socio-economic issues, a modification of the «cost-utility» analysis is proposed. For the first time, a Markov model of PD including preclinical diagnostic tests and possible neuroprotective therapy was developed and studied. Analytical outcomes of this process suggest that the idea of developing a new multimodal strategy is promising from a socio-economic point of view.

Neuropathobiology of non-motor symptoms in Parkinson disease

Parkinson disease (PD) is a multisystem disorder associated with α-synuclein aggregates throughout the central, autonomic, and peripheral nervous system, clinically characterized by motor and non-motor (NM) symptoms. The NMS in PD, many of which antedating motor dysfunction and representing a preclinical phase spanning 20 or more years, are linked to widespread distribution of α-synuclein pathology not restricted to the dopaminergic nigrostriatal system that is responsible for core motor features of PD. The pathologic substrate of NM manifestations such as olfactory, autonomic (gastrointestinal, urogenital, cardia, respiratory), sensory, skin, sleep, visual, neuropsychiatric dysfunctions (cognitive, mood, dementia), and others are critically reviewed. In addition to non-nigral brainstem nuclei, α-synuclein pathology involves sympathetic and parasympathetic, enteric, cardiac and pelvic plexuses, and many other organs indicating a topographical and chronological spread, particularly in the prodromal stages of the disease. Few animal models recapitulate NMS in PD. The relationship between regional α-synuclein/Lewy pathology, neurodegeneration and the corresponding clinical deficits awaits further elucidation. Controlled clinicopathologic studies will refine the correlations between presymptomatic and late-developing NM features of PD and neuropathology, and new premotor biomarkers will facilitate early diagnosis of PD as a basis for more effective preventive and therapeutic options of this devastating disease.