Parkinson Disease l: Introduction

Parkinson’s disease is a chronic, progressive neurodegenerative disorder that primarily affects movement. It is characterized by motor symptoms such as resting tremors, muscle rigidity, bradykinesia (slowness of movement), and postural instability. Patients may notice hand tremors at rest, stiffness during movement, or a shuffling gait. In addition to motor features, non-motor symptoms include sleep disturbances, mood and behavioral changes, constipation, and cognitive impairment, all of which gradually worsen over time.

Etiology

The exact cause is not fully understood but involves a combination of genetic and environmental factors. Genetic mutations in genes such as SNCA, LRRK2, PRKN, PINK1, DJ-1, and GBA have been associated with the disease; for example, LRRK2 mutations impair cellular waste clearance, leading to neuronal damage. Environmental exposures, including pesticides, industrial chemicals, and heavy metals, also increase risk. For example, prolonged exposure to paraquat has been specifically linked to Parkinson’s disease.

Parkinsonism

Parkinsonism refers to a group of conditions with similar motor symptoms but different causes. It may result from toxins such as manganese, carbon monoxide, or MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). Certain medications, including butyrophenones, phenothiazines, metoclopramide, reserpine, and tetrabenazine, can cause reversible Parkinsonism. Other disorders like Wilson disease, Huntington disease, multiple system atrophy, and progressive supranuclear palsy may also present with Parkinsonian features.

Risk Factors

Non-modifiable factors include increasing age (especially after 60), male sex, and family history. Modifiable risks include toxin exposure, repeated head trauma, and possibly metabolic conditions such as diabetes, though evidence remains variable.