Parkinson's disease is a chronic degenerative movement disorder.
Its a disorder of muscle tone, abnormal fluency or speed of movement (called dyskinesia) may involve excessive or involuntary movement (hyperkinesia) or slowed or absent voluntary movement (hypokinesia).
With advances in knowledge disease, boundaries may change. Occasionally, these changes are of such a magnitude that they require redefinition of the disease. In recognition of the profound changes in our understanding of Parkinson's disease (PD), the International Parkinson and Movement Disorders Society (MDS) commissioned a task force to consider a redefinition of PD.
Several critical issues were identified that challenge current PD definitions. First, new findings challenge the central role of the classical pathologic criteria as the arbiter of diagnosis, notably genetic cases without synuclein deposition, the high prevalence of incidental Lewy body (LB) deposition, and the nonmotor prodrome of PD. It remains unclear, however, whether these challenges merit a change in the pathologic gold standard, especially considering the limitations of alternate gold standards. Second, the increasing recognition of dementia in PD challenges the distinction between diffuse LB disease and PD. Consideration might be given to removing dementia as an exclusion criterion for PD diagnosis. Third, there is increasing recognition of disease heterogeneity, suggesting that PD subtypes should be formally identified; however, current subtype classifications may not be sufficiently robust to warrant formal delineation. Fourth, the recognition of a nonmotor prodrome of PD requires that new diagnostic criteria for early-stage and prodromal PD should be created; here, essential features of these criteria are proposed. Finally, there is a need to create new MDS diagnostic criteria that take these changes in disease definition into consideration 1).
see also Tremor predominant Parkinson's disease.
Parkinson's disease (PD) is the second most prevalent neurodegenerative disease.
Typically, people with Parkinson's disease receive the diagnosis in the sixth or seventh decade of life. Age is the most important risk factor for the disease, and it has been estimated that 1 to 2% of people older than 60 years of age are affected.
Epigenetic influences mediating brain iron deposition, oxidative mitochondrial injury, and macroautophagy in Parkinson disease and related conditions remain enigmatic 2).
Although the exact etiology is unknown, sporadic PD is hypothesized to be a result of genetic susceptibility interacting with environmental insult. Epidemiological studies suggest that pesticide exposure is linked to higher PD risk, but there are no studies demonstrating SN changes with chronic pesticide exposure in human subjects.
The changes detected by MRI may mark “one of the hits” leading to PD, and underlie the increased risk of PD in pesticide users found in epidemiological studies. Further human studies assisted by these imaging markers may be useful in understanding the etiology of PD 3).
Mitochondrial dysfunction has long been associated with Parkinson's disease (PD). Parkin and PINK1, two genes associated with familial PD, have been implicated in the degradation of depolarized mitochondria via autophagy (mitophagy). Here, we describe the involvement of parkin and PINK1 in a vesicular pathway regulating mitochondrial quality control. This pathway is distinct from canonical mitophagy and is triggered by the generation of oxidative stress from within mitochondria. Wild-type but not PD-linked mutant parkin supports the biogenesis of a population of mitochondria-derived vesicles (MDVs), which bud off mitochondria and contain a specific repertoire of cargo proteins. These MDVs require PINK1 expression and ultimately target to lysosomes for degradation. We hypothesize that loss of this parkin- and PINK1-dependent trafficking mechanism impairs the ability of mitochondria to selectively degrade oxidized and damaged proteins leading, over time, to the mitochondrial dysfunction noted in PD 4).
At present, the pathogenesis of Parkinson's disease is not clear, although many studies suggest that MicroRNAs play a very important role in the progress of Parkinsonism.
Many studies showed that abnormal oscillations in the cortical basal ganglia pathway is involved in the pathophysiology of Parkinson's disease (PD).
Beta band oscillations in the subthalamic nucleus (STN) have been proposed as a pathophysiological signature in patients with Parkinson's disease (PD).
Results show a correlation between local STN 8 to 35 Hz power and impairment in PD, further supporting the role of subthalamic oscillatory activity as a potential biomarker for PD 5).
Parkinson's disease (PD) is a neurodegenerative disease with a long preclinical phase.
Dynamic adaptations in synaptic plasticity are critical for learning new motor skills and maintaining memory throughout life, which rapidly decline with Parkinson's disease (PD).
Axial motor impairments are a common cause of disability in patients with Parkinson's disease, become more prominent with longer disease duration.
The disability associated with Parkinson's disease arises from a broad spectrum of motor symptoms (masked face, soft voice, tremor, small handwriting, rigidity, bradykinesia, dystonia, balance issues, and shuffling steps) and nonmotor symptoms (depression, anxiety, apathy, disordered sleep, and cognitive difficulties), as well as problems of the autonomic nervous system (sexual dysfunction, constipation, gastrointestinal problems, and orthostatic hypotension). Of every three patients diagnosed with Parkinson's disease, one will become unemployed within 1 year, and most will be unemployed after 5 years. On average, patients with Parkinson's disease will spend $1,000 to $6,000 per year on medications, and their annual risk of hospitalization exceeds 30%.
Pain is a common non-motor symptom of Parkinson's disease.
Diagnosis largely depends on clinical observation, but motor dysfunctions do not emerge until 70%-80% of the nigrostriatal nerve terminals have been destroyed. Therefore, a biomarker that indicates the degeneration dopaminergic neurons is urgently needed.
DTI and the apparent transverse relaxation rate provide different but complementary information for different parkinsonisms. Combined DTI and apparent transverse relaxation rate may be a superior marker for the differential diagnosis of parkinsonisms 6)
The mainstay of treatment is medical. In certain patients Deep Brain Stimulation (DBS) may be offered. However, DBS has been associated with post-operative neuropsychology changes, especially in verbal memory.
Before the late 1960s, pioneers sectioned the human brain's motor pathways, and later investigators intentionally ablated many basal ganglia regions with alcohol or the application of heat; this approach met with limited success, however, partly because of inaccurate, imprecise, and inconsistent targeting. Moreover, intentionally created bilateral brain lesions frequently led to irreversible deficits in speech, swallowing, and cognition. This surgical approach faded in popularity with the discovery of levodopa (dopamine replacement).
The life for patients with Parkinson's disease was dreadful. Many were institutionalized.
After levodopa, it became routine for patients with Parkinson's disease to “awaken” from frozen states, and nearly all were able to live at home. Tremors faded, stiffness waned, and many patients regained their ability to walk. Yet important and unexpected challenges emerged. The most worrisome were dopamine-related, medication-induced complications. Patients began to report fluctuations (doses wearing off), freezing (especially when walking), and dancelike movements (chorea), later termed levodopa induced dyskinesia. Many reported tremors that did not respond to pharmacotherapy. In addition, there was a growing realization that levodopa was not a cure and that the disease progressed despite miraculous “awakenings.”
Deep brain stimulation (DBS) + optimal drug therapy (ODT) in early PD may reduce the risk of clinically important worsening. These findings further confirm the need to determine if DBS + ODT is superior to medical therapy for managing symptoms, reducing the complications of medications, and improving quality of life. The FDA has approved the conduct of a large-scale, pivotal clinical trial of DBS in early stage PD 7).
Axial motor signs-including gait impairment, postural instability and postural abnormalities-are common and debilitating symptoms in patients with advanced Parkinson disease. Dopamine replacement therapy and physiotherapy provide, at best, partial relief from axial motor symptoms.
The degree of clinical improvement achieved by deep brain stimulation (DBS) is largely dependent on the accuracy of lead placement.
By applying a non-targeted and mass spectrometry-driven approach, Trezzi et al. investigated the CSF metabolome of 44 early-stage sporadic PD patients yet without treatment (DeNoPa cohort). They compared all detected metabolite levels with those measured in CSF of 43 age- and gender-matched healthy controls. After this analysis, they validated the results in an independent PD study cohort (Tübingen cohort).
They identified that dehydroascorbic acid levels were significantly lower and fructose, mannose, and threonic acid levels were significantly higher (P < .05) in PD patients when compared with healthy controls. These changes reflect pathological oxidative stress responses, as well as protein glycation/glycosylation reactions in PD. Using a machine learning approach based on logistic regression, we successfully predicted the origin (PD patients vs healthy controls) in a second (n = 18) as well as in a third and completely independent validation set (n = 36). The biomarker signature is composed of the three markers-mannose, threonic acid, and fructose-and allows for sample classification with a sensitivity of 0.790 and a specificity of 0.800.
They identified PD-specific metabolic changes in CSF that were associated with antioxidative stress response, glycation, and inflammation. The results disentangle the complexity of the CSF metabolome to unravel metabolome changes related to early-stage PD. The detected biomarkers help understanding PD pathogenesis and can be applied as biomarkers to increase clinical diagnosis accuracy and patient care in early-stage PD 8).
Sixty-nine participants with PD completed a Simon response conflict task and Behavioral Inhibition System (BIS) and Behavioral Activation System (BAS) scales based on Gray's (1987) reinforcement sensitivity theory. Analyses determined relationships between BIS, BAS, and the susceptibility to making impulsive action errors and the proficiency of inhibiting interference from action impulses.
BIS scores correlated positively with rates of impulsive action errors, indicating that participants endorsing low BIS tendencies were much more susceptible to acting on strong motor impulses. Analyses of subgroups with high versus low BIS scores confirmed this pattern and ruled out alternative explanations in terms of group differences in speed-accuracy tradeoffs. None of the scores on the BIS or BAS scales correlated with reactive inhibitory control.
PD participants who endorse diminished predilection toward monitoring and avoiding aversive experiences (low BIS) show much greater difficulty restraining fast, impulsive motor errors. Establishing relationships between motivational sensitivities and cognitive control processes may have important implications for treatment strategies and positive health outcomes in participants with PD, particularly those at risk for falling and driving difficulties related to impulsive reactions 9).
A 38-year-old male with Parkinson's disease developed intractable hemiballism in his left extremities due to a small lesion that was located adjacent to the right deep brain stimulation (DBS) lead, 10 months after bilateral subthalamic nucleus (STN)-DBS placement. He underwent a right globus pallidus internus (GPi)-DBS lead implantation. GPi-DBS satisfactorily addressed his hemiballism.
This case offered a unique look at basal ganglia physiology in human hemiballism. GPi-DBS is a reasonable therapeutic option for the treatment of medication refractory hemiballism in the setting of Parkinson's disease 10).