Summary

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by loss of dopaminergic neurons in the substantia nigra pars compacta. It is characterised by the motor features of bradykinesia, rigidity, and rest tremor, along with numerous non-motor features including constipation, anosmia, sleep disturbance, and later cognitive impairment. Diagnosis is clinical. Treatment is primarily with levodopa (most effective) or dopamine agonists, with surgical options (DBS) for advanced disease. PD progresses over years, and management requires multidisciplinary support.

Key Facts

• Definition: Neurodegenerative disorder due to dopaminergic neuron loss in substantia nigra
• Prevalence: 1-2 per 1,000; increases with age (1% >60 years)
• Diagnosis: Clinical — bradykinesia PLUS tremor or rigidity
• Hallmark Pathology: Lewy bodies (α-synuclein)
• First-Line Treatment: Levodopa (with carbidopa/benserazide)
• Specialist Input: All patients should be referred to a specialist

Clinical Pearls

"Bradykinesia is Essential": You CANNOT diagnose Parkinson's disease without bradykinesia. It must be present along with at least one of: rest tremor or rigidity.

Asymmetry is Typical: PD classically starts unilaterally. Symmetric onset or early bilateral disease should raise suspicion of atypical parkinsonism.

Non-Motor Features Precede Motor: Anosmia, constipation, REM sleep behaviour disorder (RBD), and depression often precede motor symptoms by years — the "prodromal phase."

Why This Matters Clinically

PD is the second most common neurodegenerative disorder after Alzheimer's. Early recognition allows appropriate treatment initiation, improving quality of life. Differentiating PD from atypical parkinsonian syndromes and drug-induced parkinsonism is essential.

Structured Approach

Observation:

• Facies (hypomimia)
• Tremor at rest
• Posture (flexed)
• Gait (shuffling, reduced arm swing)

Assessment of Cardinal Features:

• Bradykinesia: Finger tapping, hand movements, heel tapping (look for decrement)
• Tremor: Rest tremor (distracted); pill-rolling
• Rigidity: Assess tone (lead-pipe, cogwheeling)

Postural Stability:

• Retropulsion test (pull test) — late feature

Special Tests

Natural History

PD is progressive but variable. Most patients have good quality of life for many years with treatment. Motor complications (fluctuations, dyskinesias) typically develop after 5-10 years of levodopa therapy. Dementia and falls become prominent in advanced disease.

Outcomes

Prognostic Factors

Better Prognosis:

• Tremor-dominant subtype
• Younger onset
• No cognitive impairment
• Good levodopa response

Poorer Prognosis:

• PIGD (postural instability gait difficulty) subtype
• Older onset
• Early cognitive impairment
• Rapid motor progression

Key Guidelines

1. NICE NG71: Parkinson's Disease in Adults (2017) — Diagnosis, referral, pharmacological and non-pharmacological management.

2. Movement Disorder Society Clinical Diagnostic Criteria (2015) — Gold standard diagnostic criteria.

Landmark Trials

PD MED (2014) — Initial PD treatment

• RCT comparing levodopa vs levodopa-sparing strategies
• Key finding: Levodopa provides best early motor control; no long-term disadvantage
• Clinical Impact: Levodopa accepted as first-line for most patients

EARLYSTIM (2013) — Early DBS

• RCT comparing DBS + medical therapy vs medical therapy alone
• Key finding: DBS improves QoL in patients with early motor complications
• Clinical Impact: Supports earlier DBS referral

Evidence Strength

What is Parkinson's Disease?

Parkinson's disease is a condition where certain nerve cells in your brain that produce a chemical called dopamine gradually stop working. Dopamine helps control movement, which is why Parkinson's causes stiffness, slowness, and tremor. It can also affect other things like sleep, mood, and bowel function.

Why does it matter?

Parkinson's is a progressive condition, meaning it gradually gets worse over time. However, with the right treatment and support, most people live well for many years. Medications can significantly improve symptoms.

What are the symptoms?

Main movement symptoms:

• Tremor (shaking) — usually at rest
• Slowness of movement
• Stiffness
• Balance problems (later on)

Other symptoms:

• Loss of smell
• Constipation
• Sleep problems
• Low mood or anxiety
• Memory and thinking changes (later)

How is it treated?

1. Medications: The main treatments replace or mimic dopamine:

   • Levodopa (most effective; usually becomes necessary)
   • Dopamine agonists
   • Other tablets to smooth out responses

2. Therapies: Physiotherapy, speech therapy, occupational therapy

3. Surgery (advanced cases): Deep brain stimulation (DBS) can help control symptoms when medications aren't working well enough

What to expect

• Parkinson's progresses slowly — most people have many good years
• Medications work well at first; can be adjusted over time
• Regular follow-up with your specialist is important
• Multidisciplinary team support (physio, OT, SALT, nurses) helps maintain function

When to seek help

Contact your team or GP if:

• Symptoms are getting significantly worse
• You're having problems with medication timing
• You experience hallucinations or confusion
• Falls are increasing
• Mood is low and affecting daily life