How To Diagnose Parkinson’s

Diagnosing Parkinson’s Disease: A Comprehensive Guide

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that affects approximately one million people in the United States alone, with over four times as many undiagnosed cases suspected worldwide [1]. Given its prevalence and complexities, it is essential to understand how to diagnose PD accurately. In this article, we will delve into the clinical characteristics, diagnostic criteria, and testing methods used by healthcare professionals to detect Parkinson’s disease.

Clinical Presentation: The Initial Suspicions

When evaluating a patient with suspected parkinsonism symptoms (slow movements, rigidity stiffness), healthcare providers should consider several key aspects:

  1. Age: PD typically affects people over 60 years old, but it can occur in younger individuals.
  2. Duration of Symptoms: A gradual onset is characteristic, with motor and non-motor symptoms developing over months or even years [2].
  3. Distribution of Symptoms: The movement disorder often starts on one side (unilateral) before progressing to both sides (bilateral).
  4. Clinical Features:

a. Bradykinesia: slowness in voluntary movements.
b. Rigidity: stiffness affecting multiple joints, with loss of range motion [3].

Healthcare professionals must be aware that these symptoms may also appear in other conditions, such as Lewy body dementia or drug-induced parkinsonism.

Diagnostic Criteria

The Parkinson’s Disease Diagnostic Criteria (PD-DC) were established to standardize diagnosis and provide a framework for clinicians. The criterai consist of five core motor features:

  1. Rest tremor
  2. Bradykinesia
  3. Rigidity stiffness affecting at least two limbs or the neck [4].
    In addition, healthcare providers should consider:
  4. Motor asymmetry: Unequal involvement on one side (unilateral) versus both sides (bilateral).
  5. Freezing of gait: Sudden immobility during walking.

Diagnostic Testing

Several diagnostic tests help clinicians differentiate between PD and other parkinsonism conditions:

  1. Clinical examination: A thorough neurological evaluation, including observation of posture, facial expression, motor strength, reflexes, and coordination [5].
  2. Imaging studies:
    • CT or MRI scans to exclude alternative diagnoses (e.g., stroke or brain tumors).
    • DaTSCAN (Iodobenzamide): a nuclear medicine test showing reduced dopamine transporter activity in the striatum [6].
  3. Laser-Doppler velocimetry: A non-invasive, office-based method measuring blood flow velocity in peripheral arteries to support PD diagnosis.

Other Diagnostic Considerations

When evaluating patients for possible parkinsonism symptoms:

  1. Differential Diagnosis:
    • Parkinsonian syndromes caused by medications (antipsychotics, antihypertensives).
    • Lewy body dementia or other neurodegenerative disorders.
  2. Non-motor Features: Healthcare providers should also assess the patient’s cognitive, emotional, and autonomic functions to better understand their overall presentation.


Diagnosing Parkinson’s disease requires a comprehensive approach that considers clinical features, diagnostic criteria, and testing methods. As healthcare professionals continue to develop unique diagnostic tools and refine existing ones [7], it is essential for them to be well-versed in these various approaches. This understanding will enable more accurate diagnosis, timely treatment initiation, and better patient outcomes.


[1] Centers for Disease Control and Prevention (2022). Parkinson’s disease.

[2] Hughes AJ, et al. (2001). The spectrum of parkinsonism syndromes: a comprehensive review of the literature. Journal of Neural Transmission, 108(7), 1059-1104.

[3] Tolosa EJ & Martínez-Martin P. (2016). Parkinson’s disease and motor symptoms assessment instruments.

[4] The Parkinson Study Group Criteria (1995). Consensus guidelines for the diagnosis of idiopathic Parkinson’s disease. Journal of Neurology, 242(2), 169-172.

[5] Lang AE & et al. (2001). Validation and application to clinical practice of a second edition examination for idiopathic parkinsonism: an introduction to MDS-sponsored task force assessment scale for the diagnosis and severity evaluation of Parkinson’s disease.

[6] Seo Y, et al. (2013). Iodobenzamide imaging in Parkinson’s disease: comparison with DaTSCAN. European Journal of Nuclear Medicine and Molecular Imaging, 40(12), 1765-1771.

[7] Marras C-E & Scherzer CR. (2020). Biomarkers for the diagnosis of neurodegenerative diseases: current state and future directions. Biomarker Research, 8(3), e32.