• Clinical science

Parkinson disease


Parkinson disease (PD) is a neurodegenerative disease involving a progressive depletion of dopaminergic neurons in the basal ganglia, particularly the substantia nigra. PD usually manifests at approximately 60 years of age. Although PD is considered an idiopathic disease, genetic factors seem to play a role in about 10–15% of cases and, accordingly, familial clustering has been observed. The typical clinical picture seen in PD is called parkinsonism and features the classical cardinal symptom of bradykinesia along with resting tremor and/or rigidity. Postural instability is another frequent finding. While PD is the main cause, parkinsonism may also result from other factors, e.g., medication (secondary parkinsonism). Atypical parkinsonism may appear similar to PD, but often features additional or atypical symptoms. To date, there is no cure for PD. Symptomatic treatment includes physical therapy and, depending on patient age and individual symptoms, various medications (e.g., levodopa, dopamine agonists). In specific cases, deep brain stimulation (DBS) surgery may be beneficial.




  • Sex:
  • Prevalence: increases with age
  • Age of onset: ∼ 60 years
  • Risk factors
    • Familial history (various genes) → in approximately 10–15% of cases
    • Environmental factors (e.g., exposure to manganese and other substances)
    • Diet/metabolism (e.g., low levels of vitamin D, high iron intake, obesity)
    • Structural damage (e.g., history of traumatic brain injury)


Epidemiological data refers to the US, unless otherwise specified.




Older age, rigidity, and/or bradykinesia at onset signify a comparatively worse prognosis; tremor is a good prognostic sign!




Clinical features


  • Clinical course > 10 years; unilateral onset with persistently asymmetrical course (i.e. unilaterally pronounced symptoms) but may progress to the contralateral side
  • Parkinsonism
    • Bradykinesia/akinesia
      • Slowness of movement in combination with decreased amplitude or speed during a sequence of movement
      • Bradydiadochokinesia
    • Resting tremor (4–6 Hz)
    • Rigidity
      • Increased and persistent resistance to passive joint movement that is independent of speed of movement
      • Froment maneuver
        • The patient is asked to perform repetitive movements in the contralateral extremity (e.g., opening and closing of the left fist if the right side is examined) → Subclinical rigidity becomes more pronounced and may be detected.
      • Special form: cogwheel rigidity
  • Postural instability
  • Parkinsonian gait: shuffling gait with quickened and shortened steps
  • Unhabituated glabellar reflex
  • Signs of dystonia
  • Pyramidal signs (but normal tendon reflexes)
  • Good response to levodopa

TRAPTremor, Rigidity, Akinesia, and Postural instability

Other clinical features

Parkinsonism is required for the diagnosis of Parkinson disease! Unilateral onset is characteristic of Parkinson disease!



Parkinson disease is a clinical diagnosis!


Levodopa challenge test: (alternatively apomorphine test): The result is positive if administration of levodopa/apomorphine relieves symptoms.


Imaging is not routinely required for diagnosis, but should be considered in an atypical presentation or to rule out other underlying disorders.


Differential diagnoses

Differential diagnosis of parkinsonism
Parkinson disease (PD) Secondary parkinsonism Parkinson-plus syndromes
  • Variable, depends on the cause
Clinical features
  • Atypical parkinsonism:
    • Generally poor response to levodopa
    • Dementia, oculomotor dysfunction, and early onset of autononomic dysfunction and gait instability are common.
    • Particular syndromes show further characteristic symptoms.
  • Course: The progression is usually faster and the prognosis is usually worse than in PD.


diagnostic tests

To confirm specific etiologies:

  • Laboratory: drugs, toxins, infections, metabolic disorders
  • Imaging: NPH, vascular disorders, tumors


The differential diagnoses listed here are not exhaustive.


To date, there is no cure for PD. Treatment is aimed at relieving symptoms and should generally begin once patients develop significant functional disability (see Parkinson disease medication).

General measures

Medical therapy

For details on effects, administration, and side effects, see medication for Parkinson disease.

  • Levodopa is the drug of choice for the symptomatic therapy of Parkinson disease.
    • Dopaminergic therapy should be considered at an early stage if motor symptoms begin to substantially affect a patient's activities of daily living. The age of 65 should be considered a general point of reference rather than a fixed limit for beginning levodopa therapy.
    • In the early phase; of levodopa treatment, patients may experience a "honeymoon period" with relief of symptoms.
    • On” (parkinsonism is relieved by the levodopa) and “off” (levodopa effect wears off, parkinsonism returns) episodes are another common phenomenon.
  • Dopamine agonist in patients under the age of 65

Overstimulation of D2-receptors by levodopa or dopamine agonists may induce psychosis and hallucinations, especially in elderly patients with concurrent dementia or other psychiatric disorders!

Patients under the age of 65 with no significant comorbidities

Administration of anticholinergics may worsen existing psychiatric symptoms (particularly dementia)! There is also a risk of ischuria!

Patients over the age of 65 or multimorbid patients of any age

Levodopa is best taken between meals (e.g., 30 minutes before a meal). High protein binding properties are responsible for decreased activity!

Patients with severe motor fluctuation

Treatment of associated symptoms

Deep brain stimulation (DBS)

  • Indication: primarily recommended for patients with severe motor symptoms who respond to levodopa treatment but are not sufficiently controlled by it (or if a decrease in dosage is necessary due to side effects)
  • Adverse effects
    • Related to procedure and material: infections, hemorrhages, breakage or displacement of the electrode(s) or the lead(s)