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Parkinson Disease

Overview

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Pathology

Gross and Microscopic Changes

1. Degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNc), causing grossly visible pallor of the substantia nigra and locus coeruleus
2. Reduced striatal dopamine - dopaminergic neurons project from the SN to the striatum to control motor activity
3. Lewy bodies - intraneuronal, eosinophilic, round-to-elongated cytoplasmic inclusions composed of fine filaments of α-synuclein, neurofilaments, and ubiquitin. Neurons containing Lewy bodies are surrounded by gliosis
4. Lewy neurites - dystrophic axonal processes also containing aggregated α-synuclein

• Robbins & Kumar Basic Pathology, p.854

• Cholinergic neurons of the nucleus basalis of Meynert
• Norepinephrine neurons of the locus coeruleus
• Serotonin neurons of the raphe nuclei
• Neurons of the olfactory system, spinal cord, and peripheral autonomic nervous system
• Harrison's, p.3537

Pathogenesis

• Impaired autophagy and lysosomal degradation - several PD-associated genes (Parkin, others) play roles in endosomal trafficking and mitochondrial function
• Mitochondrial dysfunction - PINK1 (PTEN-induced putative kinase 1) is a mitochondrial gene mutated in early-onset PD
• Oxidative stress - the DJ-1 protein plays a role in cellular response to oxidative stress

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Genetics

• Adams and Victor's Principles of Neurology, 12th Ed., p.1091

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Clinical Features

Cardinal Motor Features (TRAP)

1. Tremor - rest ("pill-rolling") tremor; presenting symptom in up to 70% of patients; typically asymmetric and virtually pathognomonic. Differentiated from essential tremor (which is action-type and symmetric)
2. Rigidity - increased tone with "cogwheel" ratchety quality on passive limb movement
3. Akinesia/Bradykinesia - slowness of movement; patients describe it as limb "weakness" though strength testing is normal
4. Postural instability - late finding; contributes to falls and aspiration pneumonia

Other Motor Features

• Micrographia (small handwriting)
• Masked facies (hypomimia) - reduced facial expression
• Shuffling, narrow-based gait
• Hypophonia (soft voice)
• Drooling
• Dysphagia (subjective in 35%, objective evidence in up to 82%)
• Freezing of gait

Non-Motor Features (often underappreciated)

• Harrison's Principles of Internal Medicine 22E, p.3537

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Differential Diagnosis - Parkinsonism-Plus Syndromes

• Hallucinations (early)
• Paralysis of upward gaze (progressive supranuclear palsy, PSP)
• Early dementia (dementia with Lewy bodies)
• Early postural instability
• Early autonomic dysfunction (multiple system atrophy, MSA)
• Failure to respond to levodopa

• Textbook of Family Medicine 9e, p.1249

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Diagnosis

• DaT-SPECT (dopamine transporter scan) - shows reduced striatal uptake, most pronounced in the posterior putamen, typically asymmetric. Useful when there is diagnostic uncertainty (e.g., vs. essential tremor)
• FDG-PET - increased avidity in striatum (abnormal finding in both PD and Lewy body disease)
• α-Synuclein seeding amplification assay (SAA) - applied to CSF or skin; very high sensitivity and specificity to distinguish PD from other parkinsonisms; currently primarily a research tool, but blood-based versions are in development
• MRI/Transcranial sonography - may detect increased iron in the SNc in prodromal PD
• Genetic testing - not routine; consider in early onset (<40 years), strong family history, or specific ethnic backgrounds
• Harrison's Principles of Internal Medicine 22E, p.3537-3538

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Treatment

Pharmacological

L-DOPA Complications Over Time

1. Wearing-off / end-dose failure - the duration of each dose's benefit shortens ("on-off" fluctuations)
2. L-DOPA-induced dyskinesias - choreoathetosis, dystonia, head wagging, grimacing, blepharospasm - due to denervation hypersensitivity of striatal dopamine receptors

Surgical / Device-Aided Therapy

• Deep Brain Stimulation (DBS) - electrodes implanted in the globus pallidus or subthalamic nucleus to modulate basal ganglia circuitry. Allows significant reduction in L-DOPA dose in selected patients. Does not slow disease progression
• Levodopa-carbidopa intestinal gel (LCIG) - continuous duodenal infusion for advanced disease

Neuroprotection

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Recent Research (2025-2026)

• GBA1 genetics: A 2025 systematic review (PMID: 39927608) provides updated classification of GBA1 variants and their genotype-phenotype relationships in PD, reinforcing GBA1 as the most important genetic risk factor
• Gut microbiome: A 2025 meta-analysis using machine learning (PMID: 40335465) identified consistent gut microbiome alterations in PD, supporting the gut-brain axis hypothesis in PD pathogenesis - particularly relevant given the early involvement of the enteric nervous system in Braak staging

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Summary

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Physiotherapy Intervention in Parkinson Disease

Why Physiotherapy Matters

• Bradley and Daroff's Neurology in Clinical Practice

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Goals of Physiotherapy in PD

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APTA Clinical Practice Guideline Recommendations (2022)

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Specific Physiotherapy Interventions

1. Gait Training

• Body-weight support treadmill training (BWS-TT) is among the most effective interventions for balance and gait outcomes
• Improves stride length, cadence, gait speed, and functional mobility
• The treadmill itself acts as a form of external cueing, providing rhythmic sensory input
• Network meta-analysis (PMID: 37641007) found BWS-TT had the highest p-score for overall balance improvement

• Practised with or without cueing
• Focuses on stride length amplification, heel-strike pattern, arm swing, and turning

• A specialised physiotherapy programme targeting amplitude of movement
• Patients are trained to make large, exaggerated movements to overcome hypokinesia
• Intensive: 16 sessions over 4 weeks; shown to improve gait speed, stride length, and motor UPDRS scores

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2. External Cueing

• Metronome beats, music, or verbal prompts at a set cadence
• Patients are trained to synchronise steps to the rhythmic beat
• Immediately improves stride length and gait velocity
• Effective for FOG when used with balance training: RAS-supported balance training was superior to educational control in improving FOG frequency
• Delivered 2-5 times/week for 3-8 weeks; treadmill training with RAS outperforms overground gait training with RAS for FOG

• Transverse lines on the floor, laser lines from walking aids (e.g., U-Step walker with laser), or stripes on the ground
• Patients step over lines to trigger a normal step cycle and bypass the basal ganglia motor program deficit
• Highly effective for FOG

• Auditory + visual cueing together: greater improvements in gait speed, turning ability, and distance walked (6-Minute Walk Test)

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3. Balance Training

• Static balance exercises: single-leg standing, tandem stance, weight-shifting
• Dynamic balance exercises: stepping over obstacles, direction changes, perturbation training
• Reactive balance training: catching oneself after unexpected perturbations - most closely mimics real-world fall prevention
• Dual-task training: walking while performing a cognitive task (counting backwards, carrying a tray) - addresses the PD-specific vulnerability to cognitive-motor dual tasking
• Sensory orientation training: training with reduced visual or somatosensory input to improve vestibular reliance (foam surfaces, eyes closed)

• Anterior trunk flexion ("camptocormia") is addressed with postural extension exercises, manual correction, and taping
• Mirror feedback, wall support exercises, and proprioceptive training improve body awareness

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4. Aerobic Exercise

• Walking, cycling (including stationary bike), swimming, Nordic walking
• High-intensity interval training (HIIT) is emerging as particularly effective
• Minimum: 150 minutes/week moderate intensity, as per general exercise guidelines

• Endurance/aerobic training: small to moderate beneficial effect on motor severity (UPDRS-M MD -5.76)
• Improved cardiovascular fitness, reduced fatigue, improved mood and depression

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5. Resistance/Strength Training

• Lower limb extensor strength (quadriceps, hip abductors, calf) for gait and fall prevention
• Core stability for trunk control and posture
• Upper limb for ADL function

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6. Dance and Mind-Body Therapies

• The 2024 Cochrane network meta-analysis found dance had the greatest effect on motor severity of all exercise types (UPDRS-M MD -10.18, 95% CI -14.87 to -5.36 - a moderate effect; moderate confidence)
• Combines aerobic exercise, rhythmic cueing, balance challenge, and social engagement
• Tango is the most studied: improves balance, gait, and fear of falling
• "Several of our patients have taken up dancing and report that their balance in daily circumstances is improved." - Adams and Victor's Principles of Neurology, 12th Ed.

• Shown to improve balance and significantly reduce falls in PD in RCTs
• Effects maintained at 3-month follow-up
• "Tai chi has been found to improve balance and reduce falls as measured by objective criteria (Li et al., 2012)" - Adams and Victor's Principles of Neurology
• Recommended by most Parkinson's associations
• Most studied martial art for PD; supervised groups preferred

• Improves flexibility, balance, and reduces anxiety
• Supported by expert opinion; low-quality evidence formally

• Network meta-analysis (PMID: 37641007) found Pilates was among the best interventions for proactive balance (p-score 0.95)

• Water provides resistance without fall risk; buoyancy reduces fear
• Aquatic exercise was best for static steady-state balance (sSSB, p-score 0.85) in the 2023 NMA

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7. Task-Specific and Functional Training

• Sit-to-stand from varying chair heights (including low chairs, toilet)
• Bed mobility: rolling, getting in/out of bed
• Floor transfers: getting up from the floor after a fall
• Turning: 90° and 180° turns in small spaces; one of the highest-risk activities for FOG and falls
• Reaching: overhead and forward reaching tasks
• Stair climbing: step-by-step strategy with handrail
• Dual-task functional training: carrying items while walking, talking while ambulating

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8. Stretching and Flexibility

• Hip flexors, chest/pectoral muscles (counteracting forward stoop)
• Cervical spine and thoracic extension
• Hamstrings and calf muscles
• Shoulder rotators

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9. Speech and Respiratory Physiotherapy

• Speech therapy / LSVT LOUD: addresses hypophonia (soft voice), monotone speech, dysarthria; intensive amplitude-based approach
• Respiratory physiotherapy: diaphragmatic breathing, expiratory muscle strength training - improves breath support for speech, reduces aspiration risk
• Swallowing therapy (SLP): critical given 35-82% prevalence of dysphagia in PD

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10. Falls Prevention and Assistive Devices

• Postural instability
• Orthostatic hypotension
• Medication timing (falls in "off" periods)
• Environmental hazards
• Footwear

• Standard quad cane: useful for mild instability
• Nordic/trekking poles: bilateral support; improve trunk extension
• 4-wheeled walker (rollator): preferred over front-wheeled walker (FWW increases falls in PD)
• U-Step walker: has built-in laser line or metronome for cueing; designed specifically for PD
• Wheeled mobility: when ambulation becomes unsafe

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11. Pelvic Floor Physiotherapy

• Urinary urgency/incontinence affects up to 40% of PD patients
• Pelvic floor muscle training (PFMT): Kegel exercises, biofeedback
• Transcutaneous tibial nerve stimulation (TTNS) and percutaneous tibial nerve stimulation (PTNS): neuromodulatory approaches for bladder symptoms

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12. Telerehabilitation

• APTA guideline: moderate quality, moderate recommendation
• Video-based physiotherapy sessions are feasible and effective, particularly for homebound patients
• Falls when travelling to clinic is a risk for late-stage PD
• Home exercise apps (e.g., Parkinson's UK apps, Beats Medical, PD Warrior) supplement supervised sessions

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Exercise Dosing Principles

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Outcome Measures Used by Physiotherapists

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Disease Stage Considerations

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Key Evidence Summary

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Multidisciplinary Integration

• Neurologist: medication optimisation (exercise is most effective in "on" periods)
• Occupational therapist: ADL adaptations, fine motor training, home assessment
• Speech-language pathologist: dysphagia, voice, communication
• Physiotherapist: all motor, gait, balance, and exercise interventions above
• Psychologist/social worker: depression, anxiety, caregiver burden
• Pelvic floor PT: urinary symptoms

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Types of Parkinson Disease (Parkinsonism)

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Master Classification

PARKINSONISM
├── 1. PRIMARY (Neurodegenerative)
│   ├── A. Idiopathic Parkinson Disease (classic / sporadic PD)
│   ├── B. Genetic / Familial PD
│   └── C. Atypical Parkinsonism ("Parkinsonism-Plus")
│       ├── Multiple System Atrophy (MSA)
│       ├── Progressive Supranuclear Palsy (PSP)
│       ├── Corticobasal Degeneration (CBD)
│       └── Dementia with Lewy Bodies (DLB)
└── 2. SECONDARY (Acquired / Symptomatic)
    ├── Drug-induced parkinsonism
    ├── Vascular parkinsonism
    ├── Toxic parkinsonism (MPTP, CO, manganese)
    ├── Infectious (post-encephalitic)
    ├── Metabolic (Wilson's disease, hypothyroidism)
    ├── Structural (NPH, tumour, trauma)
    └── Other heredodegenerative disorders

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PART 1 - PRIMARY PARKINSONISM

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A. Idiopathic Parkinson Disease (IPD)

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B. Genetic / Familial Parkinson Disease

• Adams and Victor's Principles of Neurology, 12th Ed.

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C. Atypical Parkinsonism ("Parkinsonism-Plus Syndromes")

• Symptoms tend to be more symmetric
• More rapid progression
• Paucity or absence of resting tremor
• Early postural instability (falls in first year)
• Poor or absent L-DOPA response
• Neuroanatomy Through Clinical Cases, 3rd Ed.

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C1. Progressive Supranuclear Palsy (PSP)

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C2. Multiple System Atrophy (MSA)

• Orthostatic hypotension (>30 mmHg systolic drop on standing)
• Urogenital dysfunction - urinary incontinence, erectile dysfunction (often the first symptom in men)
• GI dysmotility
• Anhidrosis (central pattern on thermoregulatory sweat testing)
• REM sleep behaviour disorder (RBD)
• Stridor (from vocal cord paralysis - a dangerous, characteristic feature)

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C3. Corticobasal Degeneration (CBD) / Corticobasal Syndrome (CBS)

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C4. Dementia with Lewy Bodies (DLB)

1. Fluctuating cognition - dramatic fluctuations in alertness and attention (minutes to hours)
2. Recurrent vivid visual hallucinations (well-formed, typically people or animals)
3. Parkinsonism - usually mild, often no tremor or only slight tremor

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PART 2 - SECONDARY (ACQUIRED) PARKINSONISM

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D. Drug-Induced Parkinsonism (DIP)

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E. Vascular Parkinsonism (VP)

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F. Toxic Parkinsonism

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G. Post-Encephalitic Parkinsonism

• Von Economo's encephalitis lethargica (1918 influenza pandemic era) caused a characteristic post-infectious parkinsonism with oculogyric crises
• Patients could develop parkinsonism decades after acute encephalitis
• Now largely historical but remains in differential diagnosis; recent interest given reports of new-onset PD following SARS-CoV-2 infection

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H. Metabolic / Heredodegenerative Causes

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Comparative Summary Table

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Key Clinical Red Flags Against Idiopathic PD

• Symmetric onset
• Failure to respond to an adequate L-DOPA trial
• Early falls (within 1st year)
• Early dementia or visual hallucinations preceding motor symptoms
• Vertical gaze palsy (→ PSP)
• Prominent early autonomic failure (→ MSA)
• Prominent cerebellar signs (→ MSA-C)
• Alien limb or cortical sensory loss (→ CBD)
• Neuroleptic drug exposure (→ drug-induced)
• Liver disease or age <40 (→ Wilson's disease)
• Harrison's Principles of Internal Medicine 22E, p.3544; Textbook of Family Medicine 9e