What are the clinical features of Parkinson's disease (PD)?

From the Guidelines

Parkinson's disease is characterized by several key features including tremor at rest, bradykinesia, rigidity, and postural instability, resulting from the progressive loss of dopaminergic neurons in the substantia nigra, leading to dopamine deficiency in the basal ganglia, which disrupts normal movement control pathways in the brain. The clinical presentation of PD is characterized by resting tremor, bradykinesia, and rigidity and is related to progressive degeneration of the dopaminergic neurons in the substantia nigra projecting to the striatum 1. Other features include autonomic dysfunction, behavioral changes, and dementia. The estimated interval between initial loss of dopaminergic neurons and the appearance of symptoms is approximately 5 years (after approximately 40% to 50% of the dopaminergic neurons in the substantia nigra have been lost) 1. Some key points to consider when evaluating PD include:

• Tremor at rest, which typically begins in one limb, often the hand, and has a characteristic "pill-rolling" quality between the thumb and forefinger
• Bradykinesia, which manifests as difficulty initiating movements, reduced facial expressions (hypomimia), decreased blinking, and small handwriting (micrographia)
• Rigidity, which presents as increased muscle tone that can be "cogwheel" in nature when combined with tremor
• Postural instability, with a forward-stooped posture, shuffling gait, and difficulty with balance
• Non-motor symptoms, including cognitive impairment, depression, anxiety, sleep disorders, constipation, and autonomic dysfunction such as orthostatic hypotension It's worth noting that while the UPDRS and MDS-UPDRS scales are commonly used to evaluate motor function in PD, they may not be perfect for capturing the full range of motor symptoms, particularly in diseases like dementia with Lewy bodies (DLB) where the motor syndrome can differ from that in PD 1. However, the UPDRS scales remain a useful tool for measuring parkinsonism, and incorporating a survey for falls can provide additional valuable information. Overall, a comprehensive evaluation of PD should take into account both motor and non-motor symptoms, as well as the potential for variability in disease presentation and progression.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Mechanism of Action Parkinson’s disease is a progressive, neurodegenerative disorder of the extrapyramidal nervous system affecting the mobility and control of the skeletal muscular system. Its characteristic features include resting tremor, rigidity, and bradykinetic movements.

The clinical features of Parkinson's disease (PD) include:

• Resting tremor
• Rigidity
• Bradykinetic movements 2

From the Research

Clinical Features of Parkinson's Disease

The clinical features of Parkinson's disease (PD) can be summarized as follows:

• Primary motor symptoms:
  • Bradykinesia (slowness of movement) 3, 4, 5, 6, 7
  • Resting tremor 3, 4, 5, 6, 7
  • Rigidity (stiffness) 3, 4, 5, 6, 7
  • Postural instability (loss of balance) 4, 6, 7
• Additional motor deficits:
  • Gait disturbance 5
  • Impaired handwriting 5
  • Grip force deficits 5
  • Speech deficits 5
• Nonmotor symptoms:
  • Occur earlier than motor symptoms in some cases 6
  • Contribute significantly to patient disability 6

Disease Progression

The disease progression of PD is characterized by:

• A gradual worsening of motor symptoms over time 3
• Different rates of progression for different motor symptoms, with rigidity and bradykinesia often progressing faster than tremor 3
• The development of motor complications, such as drug-induced involuntary body movements, which can contribute to overall disability 3

Current Understanding and Management

The current understanding and management of PD can be summarized as follows:

• PD is a progressive neurodegenerative disorder characterized by the loss of dopaminergic neurons and Lewy pathology 7
• Current management strategies aim to provide symptomatic relief and slow down disease progression, but no pharmacological breakthrough has been made to protect dopaminergic neurons 7
• Deep brain stimulation, stem cell transplantation, gene editing, and gene transfer are promising approaches for potential management of the disease 7