Parkinson’s disease

Parkinson’s disease is a progressive nervous-system disorder that affects movement. It develops when nerve cells in a part of the brain called the substantia nigra become impaired or die. These cells normally produce dopamine, a chemical messenger that helps control movement. As dopamine levels fall, movement symptoms appear.

Parkinson’s usually begins after age 60, although early-onset disease can occur. Classic motor features include tremor at rest, slowness of movement (bradykinesia), rigidity, and postural instability. Non-motor symptoms — such as loss of smell, constipation, sleep disorders, depression, and cognitive changes — are also common and may precede motor signs by years.

There is no cure, but medicines, therapies, and, in selected cases, deep-brain stimulation can substantially improve quality of life for many years.

Motor symptoms often start on one side of the body and later become bilateral. They include:

• Tremor — typically a rhythmic tremor at rest, often beginning in a hand or fingers (“pill-rolling”)
• Bradykinesia — slowed movement that can make simple tasks difficult and time-consuming
• Rigid muscles — stiffness that may limit range of motion and cause pain
• Impaired posture and balance — stooped posture, shuffling gait, falls
• Loss of automatic movements — reduced blinking, arm swing, or facial expression (masked face)
• Speech changes — softer, faster, monotone, or hesitant speech
• Writing changes — small, cramped handwriting (micrographia)

Non-motor symptoms include hyposmia, constipation, REM-sleep behavior disorder, depression, anxiety, fatigue, urinary symptoms, orthostatic hypotension, and cognitive impairment or dementia in later stages.

In most cases the cause is unknown (idiopathic Parkinson’s disease). Pathologically, the disease is characterized by loss of dopamine neurons and the presence of Lewy bodies containing aggregated alpha-synuclein.

Contributing factors include:

• Genetic mutations (SNCA, LRRK2, PARK7, PINK1, PRKN, and others) — more often relevant in early-onset or familial cases
• Environmental exposures (pesticides, certain solvents) in some studies
• Age-related cellular vulnerability
• Possible roles for mitochondrial dysfunction, oxidative stress, and inflammation

Secondary parkinsonism can result from medications, strokes, toxins, or other neurodegenerative diseases and must be distinguished from idiopathic Parkinson’s.

Risk factors include:

• Age (strongest risk factor)
• Family history / certain genetic variants
• Male sex
• Exposure to pesticides or certain industrial chemicals
• Prior head trauma (in some studies)
• Reduced risk has been associated with caffeine intake and smoking in observational studies (smoking is not recommended)

As Parkinson’s progresses, complications may include:

• Difficulty thinking and dementia
• Depression and emotional changes
• Swallowing problems and aspiration risk
• Sleep disorders and daytime sleepiness
• Bladder problems and constipation
• Blood-pressure drops on standing
• Fatigue and pain
• Sexual dysfunction
• Falls and injuries
• Motor fluctuations and dyskinesias related to long-term levodopa therapy

There is no proven way to prevent Parkinson’s disease. Regular physical exercise is associated with better outcomes and may have a modest protective effect. Avoiding unnecessary pesticide exposure is reasonable. Research into neuroprotective strategies continues.

Diagnosis is clinical, based on history and neurologic examination. There is no single definitive laboratory test. Supportive elements include:

• Presence of bradykinesia plus rest tremor or rigidity
• Clear response to dopaminergic medication
• DaTscan (dopamine transporter SPECT) in uncertain cases to confirm nigrostriatal degeneration
• MRI to exclude structural mimics
• Exclusion of red flags that suggest alternative diagnoses (early severe autonomic failure, early falls, cerebellar signs, etc.)

Referral to a movement-disorder specialist is helpful when the diagnosis is unclear or management is complex.

See a doctor if you notice tremor, stiffness, slowed movement, or changes in gait or handwriting that interfere with daily activities. Early evaluation by a neurologist, ideally a movement-disorder specialist, improves diagnostic accuracy and treatment planning.

Treatment is individualized and evolves over time:

Medicines

• Levodopa (combined with carbidopa) — the most effective symptomatic therapy
• Dopamine agonists (pramipexole, ropinirole, rotigotine)
• MAO-B inhibitors (selegiline, rasagiline, safinamide)
• COMT inhibitors (entacapone, opicapone) to prolong levodopa effect
• Amantadine for dyskinesia and mild symptoms
• Anticholinergics for tremor in selected younger patients
• Medicines for non-motor symptoms (depression, sleep, bladder, etc.)

Advanced therapies

• Deep-brain stimulation (DBS) of the subthalamic nucleus or globus pallidus for motor fluctuations and dyskinesia
• Focused ultrasound in selected cases
• Continuous levodopa-carbidopa intestinal gel or subcutaneous infusions in advanced disease

Rehabilitation — physical, occupational, and speech therapy (including Lee Silverman Voice Treatment) are essential.

Helpful daily strategies:

• Take medicines on a consistent schedule; do not stop suddenly
• Stay active with regular aerobic and strength exercise; consider physical therapy or community exercise programs designed for Parkinson’s
• Practice large-amplitude movements and clear speech
• Prioritize sleep and treat sleep disorders
• Prevent falls (home safety, balance work, appropriate footwear)
• Maintain social engagement and address mood symptoms early
• Work with a multidisciplinary team (neurology, therapy, nursing, social work)

Bring:

• Description of motor and non-motor symptoms and when they began
• List of all medicines and previous Parkinson’s treatments
• Notes about response to current medicines (wearing-off, dyskinesia)
• Questions about diagnosis, medication options, exercise, DBS eligibility, and support resources
• A family member or care partner when possible