What is Parkinson's disease (PD)?

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Last updated: March 26, 2025View editorial policy

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From the Guidelines

Parkinson's disease (PD) is a neurodegenerative disease and movement disorder characterized by progressive degeneration of the dopaminergic neurons in the substantia nigra/striatum, leading to motor symptoms of tremor, rigidity, postural instability, and bradykinesia. The clinical presentation of PD is complex and involves various symptoms, including:

  • Resting tremor
  • Bradykinesia
  • Rigidity
  • Autonomic dysfunction
  • Behavioral changes
  • Dementia As noted in the study by 1, PD is the most common cause of Parkinsonism, with an annual incidence estimated at 10 to 18/100,000 in the total population and peak age of onset between 60 to 70 years. The disease is characterized by the deposition of Lewy bodies, predominantly composed of alpha-synuclein and ubiquitin, in the substantia nigra and other deep gray nuclei.

The diagnosis of PD can be challenging, and imaging remains an essential diagnostic tool in the evaluation of a patient presenting with Parkinsonian symptoms, as stated in the study by 1. It is essential to differentiate PD from other Parkinsonian syndromes, such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and corticobasal degeneration (CBD), which have distinct clinical features and prognoses.

In terms of management, while the study by 1 does not provide specific treatment recommendations, the primary goal is to manage symptoms and improve quality of life. This typically involves a multidisciplinary approach, including medications, physical therapy, and speech therapy. The most effective treatment strategy should be based on the individual patient's needs and should aim to maximize functional ability and minimize disability.

From the Research

Definition and Characteristics of Parkinson's Disease

  • Parkinson's disease (PD) is a complex neurologic disorder that involves motor and nonmotor brain functions 2.
  • It is the second most common neurodegenerative disease after Alzheimer disease 2.
  • PD is characterized by a progressive loss of dopamine neurons of the central nervous system 3.
  • The disease determines a significant disability due to a combination of motor symptoms and non-motor symptoms 3.

Motor and Nonmotor Symptoms

  • Motor symptoms include resting tremor, cogwheel rigidity, extreme slowness of movement, shuffling gait, and impaired balance 2.
  • Nonmotor symptoms include depression, hallucinations, and sleep disturbances that seriously affect quality of life 2.
  • Other non-motor symptoms include sleep disorders, hallucinations, psychosis, and compulsive behaviors 3.

Pathogenesis and Molecular Mechanisms

  • The etiology of dopaminergic neuronal demise is elusive, but a combination of genetic susceptibilities and environmental factors seems to play a critical role 4.
  • Recent findings implicate mitochondrial dysfunction, oxidative damage, abnormal protein accumulation, and protein phosphorylation as key molecular mechanisms compromising dopamine neuronal function and survival 4.
  • The discovery of genes linked to rare familial forms of disease and studies from experimental animal models has provided crucial insights into molecular mechanisms in disease pathogenesis 4.

Treatment and Management

  • There is no cure for PD, but management of motor and nonmotor symptoms can improve quality of life 2.
  • Carbidopa-levodopa is an effective initial treatment for motor symptoms of rigidity and resting tremors 2.
  • Treatments for nonmotor symptoms include antidepressants, antipsychotics, and drugs for dementia 2.
  • Monoamine oxidase B inhibitors have a favorable pharmacokinetic profile, improve the dopamine deficient state, and may have neuroprotective properties 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Parkinson's disease.

Human molecular genetics, 2007

Research

Monoamine Oxidase B Inhibitors in Parkinson's Disease.

CNS & neurological disorders drug targets, 2017

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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