How do you assess Parkinson's disease in a patient?

Assessment of Parkinson's Disease

Parkinson's disease is diagnosed clinically by identifying bradykinesia (slowness of movement) plus at least one of the following: resting tremor or rigidity, with I-123 ioflupane SPECT/CT (DaTscan) serving as the definitive confirmatory test when clinical presentation is unclear. 1, 2

Essential Clinical Diagnostic Criteria

The diagnosis requires the presence of bradykinesia as the mandatory feature, accompanied by at least one additional cardinal motor sign 1, 3, 4:

• Resting tremor (typically 4-6 Hz, present at rest, diminishes with action) 3, 5
• Rigidity (lead-pipe or cogwheel resistance to passive movement) 1, 3
• Postural instability (appears later in disease, not useful for early diagnosis as it emerges at Hoehn & Yahr stage 3) 3, 4

Physical Examination Technique for Rigidity Assessment

To properly assess rigidity, use this systematic approach 1:

• Instruct the patient to completely relax while you passively move their limbs through full range of motion 1
• Test both upper and lower extremities, comparing sides for asymmetry (PD typically presents asymmetrically) 1
• Move joints at varying speeds throughout the entire range of motion 1
• Note constant resistance throughout movement (lead-pipe rigidity) or ratchet-like jerky resistance when combined with tremor (cogwheel rigidity) 1
• Use activation maneuvers (have patient open/close the opposite hand) to enhance detection of subtle rigidity that might otherwise be missed 1, 6

Bradykinesia Assessment

Evaluate bradykinesia across multiple domains 1:

• Fine motor tasks: buttoning clothes, writing (micrographia), using utensils 1
• Gross motor activities: walking, turning, rising from chair 1
• Facial expressions: reduced spontaneous facial movement (hypomimia) 5
• Speech: reduced volume and clarity (hypophonia, dysarthria) 1, 5

Red Flags Suggesting Alternative Diagnoses

Certain features should prompt consideration of atypical parkinsonian syndromes rather than idiopathic PD 1, 6:

• Vertical gaze palsy (especially downward gaze limitation) suggests Progressive Supranuclear Palsy 1, 6
• Asymmetric rigidity with alien hand phenomenon suggests Corticobasal Syndrome 1, 6
• Early postural instability, falls, or dementia (within first year) suggests atypical parkinsonism 5
• Poor or absent response to levodopa strongly suggests non-PD diagnosis 5
• Early autonomic dysfunction (severe orthostatic hypotension, urinary incontinence) suggests Multiple System Atrophy 5
• Ataxia, ophthalmoparesis, or pyramidal signs indicate alternative diagnoses 5

Diagnostic Imaging Algorithm

When clinical diagnosis remains uncertain after thorough examination 2:

First-line imaging: I-123 ioflupane SPECT/CT (DaTscan) 2

• Shows decreased radiotracer uptake in striatum (putamen before caudate) in PD 1
• A normal DaTscan essentially excludes all Parkinsonian syndromes and supports diagnoses of essential tremor or drug-induced parkinsonism 6, 2
• Abnormal DaTscan confirms dopaminergic deficit but cannot distinguish PD from atypical parkinsonism 2

MRI brain without contrast 1, 2

• Optimal for ruling out structural causes (tumors, vascular disease, normal pressure hydrocephalus) 1
• Often normal in early PD but may show characteristic patterns in atypical parkinsonism 2
• Superior soft tissue characterization compared to CT 2

FDG-PET/CT brain 2

• Useful for discriminating Progressive Supranuclear Palsy from idiopathic PD based on metabolic patterns 2
• Shows hypometabolism in medial frontal cortex, anterior cingulate, striatum, and midbrain in PSP 2

Critical Pitfalls to Avoid

Drug-induced parkinsonism must be excluded first 1, 6:

• Review all medications, particularly antipsychotics (typical and atypical), antiemetics (metoclopramide, prochlorperazine), and calcium channel blockers 6
• Drug-induced parkinsonism typically presents symmetrically, lacks resting tremor, and resolves after medication discontinuation 6

Failure to detect subtle rigidity 1:

• Always use activation maneuvers with the contralateral limb 1
• Test when patient is truly relaxed, not voluntarily resisting 1
• Don't confuse spasticity (velocity-dependent) with rigidity (constant throughout movement) 1

Premature diagnosis before adequate observation period 3, 4:

• Symptoms typically appear after 40-50% of substantia nigra dopaminergic neurons are lost 1
• Consider longitudinal follow-up when diagnosis is uncertain rather than immediate imaging 3

Monitoring Nutritional and Functional Status

Regular monitoring throughout disease course is essential 7:

• Body weight changes (both loss and gain occur; weight loss associated with disease progression) 7
• Vitamin status: vitamin D, folic acid, and vitamin B12 supplementation needs 7
• Dysphagia screening (present in 60-80% but often asymptomatic) 7
• Nutritional risk assessment (15% of community-dwelling PD patients are malnourished, 24% at medium-high risk) 7

Assessment Scales for Disease Severity

Unified Parkinson's Disease Rating Scale (UPDRS) is the standard clinical assessment tool 7, 8, 9:

• Part I: Mentation (cognitive function, behavior, mood) 9
• Part II: Activities of Daily Living (13 questions, scored 0-4 each, maximum 52) 9
• Part III: Motor examination (27 questions for 14 items, maximum score 108) - assesses tremor, rigidity, bradykinesia, postural instability across body regions 8, 9
• Part IV: Complications of therapy (dyskinesias, motor fluctuations) 8

The Movement Disorder Society-UPDRS (MDS-UPDRS) is a newer version with improved evaluation of non-motor aspects, freezing of gait, and tremor subtypes 7.