Parkinson disease and Secondary parkinsonism F017

Current RMA Instruments:

Changes from previous Instruments:

ICD Coding:

• ICD-10-AM Codes: G20. G21.9

Brief description

This SOP covers primary Parkinson disease and Secondary parkinsonism, but not parkinsonism that occurs as part of a broader neurological condition. 

Parkinson disease (PD) is a neurodegenerative disorder caused by the progressive loss of dopamine-producing neurons in the substantia nigra of the brain. Clinically, it is characterised by a combination of:

• bradykinesia (slowness of movement)
• resting tremor
• muscular rigidity
• postural instability

Non-motor symptoms can include disturbances in sleep, mood, or autonomic function (e.g. blood pressure, heart rate etc). Parkinson disease involves gradual progression of symptoms, and the diagnosis is often supported by a sustained response to the medication levodopa. 

Pathologically, Parkinson disease features dopaminergic neuronal loss and the presence of Lewy bodies. The SOP specifically excludes parkinsonism caused by other primary neurodegenerative diseases and the Parkinson-plus syndromes (e.g. multiple system atrophy, progressive supranuclear palsy, corticobasal degeneration). 

Secondary parkinsonism refers to parkinsonism symptoms caused by an identifiable external factor, most commonly medications that block dopamine pathways (often antipsychotic medications used for conditions such as schizophrenia). Secondary parkinsonism shares the same clinical motor features as PD but has a different underlying cause. 

It is important to note that the term 'parkinsonism' may refer to Parkinson disease, secondary parkinsonism or parkinsonian features occurring as part of a wider disease process. Parkinson's syndrome is a similar non-specific term. Because the SOP onset and worsening factors differ between Parkinonson's disease and Secondary parkinsonism, it is essential to determine which condition is present in order to consider the relevant factors. Any ambiguity regarding the nature of the condition involved would be best clarified by seeking medical advice. 

Confirming the diagnosis

The diagnosis of Parkinson disease or Secondary parkinsonism is primarily established clinically- based on detailed history and neurological examination. There is no single definitive diagnostic test. 

Investigations such as neuroimaging (e.g. MRI or CT brain) may be used to exclude other causes of parkinsonian symptoms. 

Assessment and diagnostic confirmation will require input from a specialist neurologist or geriatrician. 

Additional diagnoses covered by SOP

• Nil

Conditions not covered by SOP

• Benign essential tremor #
• Dementia pugilistica *
• Psychogenic parkinsonism #
• Parkinsonism in other primary neurodegenerative diseases, including:
  • Creutzfeldt-Jacob disease #
  • Huntington disease *
  • Multiple system atrophy #
  • Motor neurone disease #
  • Neurosyphilis #
  • Wilson disease #
• Parkinson Plus diseases including:
  • Alzheimer's disease *
  • Dementia or neurocognitive disorder with Lewy bodies #
  • Corticobasal degeneration #
  • Frontotemporal dementia #
  • Progressive supranuclear palsy #

* another SOP applies

# non-SOP condition

Clinical onset

The clinical onset of parkinsonism refers to the earliest point in time, as identified by the treating clinician, when the core features consistent with Parkinson disease or Secondary parkinsonism were first observed. These features typically include bradykinesia (slowness of movement), muscular rigidity and a resting tremor. Postural instability sometimes appears at a later stage. 

Clinical worsening

Parkinonson disease is a progressive neurodegenerative disorder, and gradual worsening over time is part of its natural history. The rate of progression varies between individuals and can be difficult to predict. Clinical worsening may present as increasing severity of the motor symptoms, the escalation of non-motor symptoms, or a sudden or more rapid decline compared with the previously observed pattern. 

The course of Secondary parkinsonism depends largely on the underlying cause. Drug-induced parkinsonism is often reversible once the causative medication is reduced or stopped. although symptoms may still persist or progress in some individuals. Cases resulting from a one-off insult (e.g. toxin exposure or structural brain injury) may remain relatively stable or progress slowly, depending on the extent of the original injury.  

For both Parkinson disease and Secondary parkinsonism, the pattern of progression can vary widely- particularly with Parkinson disease. Establishing whether a person has experienced worsening beyond the expected course requires review by a neurologist experienced in movement disorders.