You are here

Parkinson's Disease and Secondary Parkinsonism F017

Last amended 
24 November 2023
Current RMA Instruments:
Reasonable Hypothesis SOP
55 of 2016
Balance of Probabilities SOP
56 of 2016 as amended
Changes from previous Instruments:

SOP Bulletin 239.pdf

ICD Coding:
  • ICD-10-AM Codes: G20. G21.9
Brief description

This SOP covers primary Parkinson's disease and some but not all forms or parkinsonism.

  • Parkinson's disease means a neurological condition featuring a combination of tremor at rest, muscle rigidity and slow movement, occurring without other disease manifestations, and generally of unknown cause.
  • For SOP purposes secondary parkinsonism covers a condition mimicking Parkinson's disease, of identifiable cause, but not cases where the parkinsonian features occur in association with a wider neurological disease process, such as parkinsonism in Alzheimer's disease. 
  • In more general usage the term parkinsonism may be used to denote Parkinson's disease, secondary parkinsonism, or parkinsonian features as part of a wider neurological process.
  • Parkinson's syndrome is a non-specific term covering both Parkinson's disease and secondary parkinsonism.

Approximately 75% of cases with parkinsonian features are due to Parkinson's disease.

Where the parkinsonism is part of a wider disease process this should be apparent to the treating doctor and there should not be difficulty in distinguishing such a condition from Parkinson's disease or secondary parkinsonism.

Secondary parkinsonism is uncommon except for that resulting from drug treatment for psychoses, particularly schizophrenia.  In such cases onset is usually within 3 months of starting treatment and the condition usually resolves within a few months of stopping treatment.

If it is unclear which type of parkinsonism is present you should consult a medical officer for advice.

Confirming the diagnosis

The diagnosis is made based on the clinical presentation and there are no definitive tests.  Investigations such as neuroimaging may be needed to rule out other conditions.  Specialist opinion will generally be required to confirm the precise diagnosis.

The onset factors either apply to Parkinson's disease or secondary parkinsonism only, or have different time requirements for Parkinson's disease compared with secondary parkinsonism.  You will need to know which condition is present to apply the SOP factors.

The relevant medical specialist is a neurologist or geriatrician.

Additional diagnoses covered by SOP
  • Paralysis agitans
Conditions not covered by SOP
  • Benign essential tremor#
  • Dementia pugilistica*
  • Psychogenic parkinsonism#
  • Parkinsonism in other primary neurodegenerative diseases, including:
    • Alzheimer's disease*
    • Corticobasilar degneration#
    • Dementia with lewy bodies#
    • Frontotemporal dementia#
    • Huntington's chorea*
    • Multiple system atrophy#
    • Neurosyphilis#
    • Progressive supranuclear palsy#

* another SOP applies

# non-SOP condition

Clinical onset

Clinical onset will be at the time of diagnosis, or may be able to be backdated to when the characteristic triad of features (tremor, rigidity and slow movement) was first noted.

Clinical worsening

The natural history of Parkinson's disease is for gradual progression, but at variable speed that is difficult to predict.  Worsening may be manifest by a sudden or more rapid deterioration.

The course of secondary parkinsonism depends largely on the casual factor/s.  Drug-induced parkinsonism is usually reversible but may persist or progress.  Other cases involving a one-off insult tend to remain fairly stable or progress slowly. 

Specialist opinion is likely to be needed to establish whether there has been worsening beyond the normal course of the disease.