Evaluation for Parkinson's Disease

Initial Clinical Diagnosis

Parkinson's disease diagnosis is clinically based on the presence of bradykinesia combined with either rest tremor, rigidity, or both. 1, 2

Assess for the triad of rigidity and bradykinesia together, which has a positive likelihood ratio of 4.5 for PD diagnosis 3
Screen for prodromal features including REM sleep behavior disorder, hyposmia (loss of smell), and constipation, as these can precede motor symptoms by years 1, 2
Inquire about specific functional impairments with high diagnostic value:
- Trouble turning in bed (positive LR 13) 3
- Difficulty opening jars (positive LR 6.1) 3
- Problems rising from a chair (positive LR 1.9-5.2) 3
- Micrographia or small handwriting (positive LR 2.8-5.9) 3
- Shuffling gait (positive LR 3.3-15) 3
- Loss of balance (positive LR 1.6-6.6) 3
Evaluate psychological symptoms including depression, anxiety, and cognitive decline, as these are common non-motor manifestations 1

Perform the glabella tap test (positive LR 4.5), which is highly specific for parkinsonism 3
Assess heel-to-toe walking (positive LR 2.9 when impaired) 3
Examine for rigidity in all limbs, though this has more modest diagnostic value (positive LR 0.53-2.8) 3
Observe for rest tremor, though tremor alone has variable diagnostic accuracy (positive LR 1.3-17 depending on presentation) 3
Document bradykinesia through repetitive movements like finger tapping or hand opening/closing 1, 2

Reserve ancillary testing for patients with atypical presentations or diagnostic uncertainty. 2

Order ioflupane (DaTscan) SPECT/CT when the presence of parkinsonism is uncertain to differentiate true parkinsonian syndromes from essential tremor or drug-induced tremor 4
A normal DaTscan essentially excludes parkinsonian syndromes including PD, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration 4
An abnormal DaTscan shows decreased radiotracer uptake in the striatum, typically progressing from putamen to caudate nuclei, but cannot distinguish between different parkinsonian syndromes 4

MRI brain without contrast is the optimal anatomic imaging modality due to superior soft-tissue characterization and sensitivity to iron deposition 4
MRI is primarily useful for excluding other causes of parkinsonism such as cerebrovascular disease, multiple system atrophy, or progressive supranuclear palsy rather than confirming PD 4, 5
Advanced MRI techniques at 7-Tesla can demonstrate substantia nigra changes but are not yet standard clinical practice 4

Identify the disease subtype at diagnosis as this determines prognosis and treatment approach. 1

Mild motor-predominant subtype (49-53% of patients): Mild symptoms, good response to dopaminergic medications, slower progression 1
Diffuse malignant subtype (9-16% of patients): Prominent early motor and non-motor symptoms, poor medication response, faster progression 1
Intermediate subtype: Falls between the above two categories 1

Screen all PD patients with Hoehn & Yahr stage above II for dysphagia, as over 80% develop swallowing problems during disease course. 4

Screen regardless of disease stage if any of the following are present 4:

Use a PD-specific questionnaire such as the Swallowing Disturbance Questionnaire (SDQ) with 81% sensitivity and 82% specificity 4
Alternatively, measure average volume per swallow: Have patient drink 100 mL water in usual manner; PD patients average 13 mL per swallow versus 21 mL in controls 4
If screening is positive, proceed to instrumental assessment with FEES (fiberoptic endoscopic evaluation of swallowing) as first choice, or videofluoroscopic swallow study if FEES unavailable 4

Monitor nutritional status regularly with particular attention to body weight changes. 6

Check vitamin B12 and folate levels, as levodopa treatment is associated with elevated homocysteine and lower B vitamin levels 4
Assess for constipation, which is both a prodromal feature and ongoing management issue 1, 2
Screen for cognitive impairment, as this influences rehabilitation approach and medication management 6

Do not rely on tremor alone for diagnosis, as it has highly variable diagnostic accuracy and is absent in some PD patients 3
Recognize that silent aspiration is very common in PD and cannot be detected by clinical assessment alone, requiring instrumental evaluation 4
Be aware that only 20-40% of PD patients spontaneously report dysphagia despite 82% having objective swallowing dysfunction 4
Remember that response to dopaminergic medication supports but does not confirm PD diagnosis, as documentation of this response is part of diagnostic criteria 5