The term ‘Parkinson's disease’ was first described by physician James Parkinson in 1817. It is defined as a ‘chronic, progressive neurodegenerative condition resulting from the loss of the dopamine-containing cells of the substantia nigra’ (National Institute for Health and Care Excellence (NICE, 2023). Also known as idiopathic Parkinson's disease, it is the most common neurological movement disorder in the world (Parkinson's UK, 2023a; World Health Organization (WHO), 2023). The prevalence of the disease has doubled in the last 25 years and this figure is predicted to increase by 23.9% annually (Parkinson's UK, 2023a). The current prevalence in the UK is expected to be over 172 000 by 2030, when it is anticipated that 1 in every 37 people will be diagnosed (Parkinson's UK, 2018).
While it can occur at any age, most cases develop in those aged 50 and over, and the overall incidence increases with age. Young-onset Parkinson's develops before the age of 50 (Parkinson's UK, 2018; NICE, 2023). It affects both men and women, but is most common in men, with prevalence up to 1.5 times higher (NICE, 2023). Research is ongoing to determine the possible causes, but environmental factors, including exposure to specific chemicals and air pollution, are thought to be risk factors. The condition can be genetically inherited, but the number of people who develop it solely due genetic history is small (WHO, 2023). Anyone with suspected Parkinson's should be referred untreated to a specialist (NICE, 2017).
There are two main sub-types of Parkinson's disease: tremor dominant and postural instability gait difficulty or disturbance (PIGD).
Tremor dominant Parkinson's typically presents unilaterally in an upper limb – usually the hand – and is evident when the limb is resting (also known as a pill rolling tremor). Tremor can be present elsewhere (for example, tongue, chin and lower limb) (Parkinson's UK, 2023a). Around 75% of people experience resting tremor with Parkinson's
PIGD presents first with balance problems and rigidity rather than with tremor. As such, this group have an increased risk of falls at an earlier stage of the condition (Stebbins et al, 2013; Heusinkveld et al, 2018; Kouliet al, 2018; Dirkx and Bologna, 2022; Parkinson's UK, 2023c).
Symptoms are separated into two types: motor (affecting movement); and non-motor (non-movement-related) (NICE, 2022); however, there are over 40 known symptoms (Parkinson's UK, 2023c). Podromal symptoms can occur up to 20 years before motor symptoms are evident, and include anxiety, hyposmia (a reduction in olfactory function), constipation and REM sleep behaviour disorder (Chaudhuri et al, 2006; Ali and Morris, 2015; Mantri and Morley, 2015; Sui et al, 2019) (Table 1).
Table 1. Parkinson's disease symptoms (WHO, 2023)
| Motor symptoms | Non-motor symptoms |
|---|---|
| Slow movement | Cognitive impairment |
| Tremor | Mental health disorders |
| Involuntary movement | Dementia |
| Rigidity | Sleep disorders |
| Trouble walking | Pain |
| Imbalance | Sensory disturbances |
Parkinsonism
Parkinsonism is an umbrella term for conditions that present with symptoms typically seen in Parkinson's disease (which accounts for around 85% of cases of parkinsonism) (McFarland and Hess, 2017; NICE, 2023). Common classifications of parkinsonism include secondary, genetic or atypical and Parkinson-plus syndromes (McFarland and Hess, 2017; Parkinson's UK, 2023d).
Secondary syndromes
- Cerebrovascular disease (known as vascular parkinsonism)
- Drug-induced parkinsonism (caused by medications such as antipsychotics and certain anti-emetics)
- Normal pressure hydrocephalus.
Genetic syndromes
- Huntington's disease
- Wilson's disease.
Atypical and Parkinson-plus syndromes
- Corticobasal degeneration
- Multiple system atrophy
- Progressive supranuclear palsy
- Lewy body dementia.
Some forms of atypical parkinsonism can be difficult to diagnose in the early stages and, in some cases, diagnosis can only be confirmed as the condition progresses and atypical features present (Ali and Morris, 2015; McFarland and Hess, 2017). Symptoms of atypical parkinsonism may develop more aggressively than typical Parkinson's disease, and will not respond as effectively (if at all) to medication (McFarland and Hess, 2017; Parkinson's UK, 2023d).
Assessment and diagnosis
Diagnosis of Parkinson's disease is determined by a combination of physical assessment and clinical examination as there is no specific test (NICE, 2017). Assessment includes:
- General physical assessment and blood testing
- Review of medical history and co-morbidity
- Specialised assessment; for example, the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) (Daniel and Lees, 1993; Goetz et al, 2008)
- Scans such as CT and MRI to exclude other causes.
Where there is a degree of clinical uncertainty; for example, whether the condition is Parkinson's disease, essential tremor or drug-induced parkinsonism, a dopamine transporter scan (DaTSCAN) may be considered (NICE, 2017). A DaTSCAN reviews dopamine transport function in the brain and can be helpful in supporting or refuting a diagnosis of Parkinson's disease (Isaacson et al, 2021).
Pharmacological treatment
When motor symptoms appear, around 60–80% of dopamine producing cells are already lost, and medication will only replace a small amount of these (National Institute of Neurological Disorders and Stroke (NINDS), 2023). Most people will require medication for their condition, and there are many formulations and types of medication available.
‘As patients may only be seen once or twice per year by specialist services, timely communication between primary and secondary care is vital to effectively manage acute issues’
In practice, there is a debate as to whether medication should be prescribed early in the condition or whether it should be initiated later. There is no definitive answer to this, and it remains a decision to be made between the clinician and the patient; however, if medication is not taken, it is important to note that it will not change the progression of the condition (Nutt and Wooten, 2005; Connolly and Lang, 2014; NINDS, 2023; Parkinson's UK, 2023e). Before prescribing treatment, the following factors should be considered (NICE, 2017):
- Co-morbidity/concurrent medication (consider cognitive state also with a view to potential side effects)
- Potential side effects of medication and impact on activities of daily living
- Age
- Pregnancy planning
- Current lifestyle – job, living situation, driving
- Impulsive or compulsive behaviours (such as gambling and alcoholism).
Treatment options must be fully discussed with the patient and, wherever possible, their support circle, including family or significant others. This is particularly important if psychiatric side effects are a possibility and the patient is unaware that these are occurring.
Treatment regimens for Parkinson's disease can be complex, particularly as the condition progresses, and are best managed by a specialist team.
As patients may only be seen once or twice per year by specialist services, timely communication between primary and secondary care is vital to effectively manage acute issues, such as urinary tract infections (UTIs) and constipation, suggested medication changes, and referrals to multidisciplinary teams and mental health provision.
While many specialist Parkinson's services provide hospital and community support, telephone access and virtual appointments, not all areas have these in place. Charitable organisations such as Parkinson's UK (www.parkinsons.org.uk) can be a valuable resource for providing support, specialist information (including discussion of medication side effects) and signposting for patients, their family and health professionals.
First-line recommended medication
NICE (2017) recommends three initial pharmacological treatment options for Parkinson's as first-line: levodopa; dopamine agonists; and monoamine oxidase B (MAO-B) inhibitors. Treatment options depend on symptoms and potential side effects, as shown in Table 2.
Table 2. Potential benefits and harms of dopamine agonists, levodopa and MAO-B inhibitors (NICE, 2017)
| Motor symptoms | Levodopa | Dopamine agonists | Monoamine oxidase B (MAO-B) inhibitors |
|---|---|---|---|
| Motor symptomsActivities of daily livingMotor complicationsAdverse events(Excessive sleepiness, hallucinations, and impulse control disorders; see the summary of product characteristics for full information on individual medicines) | More improvement in motor symptomsMore improvement in activities of daily livingMore motor complicationsFewer specified adverse events | Less improvement in motor symptomsLess improvement in activities of daily livingFewer motor complicationsMore specified adverse events | Less improvement in motor symptomsLess improvement in activities of daily livingFewer motor complicationsFewer specified adverse events |
Levodopa helps increase some of the dopamine that is depleted in the brain and is the nearest oral medication form to dopamine (Connolly and Lang, 2014). Dopamine agonists work by mimicking the action of levodopa, while MAO-Bs work by preventing enzymes from breaking down dopamine, ensuring that more is readily available (Parkinson's UK, 2023e). There are multiple formulations and brands available, but if a patient starts on a branded medication this should be continued rather than switching to a generic brand, as worsening symptoms have been reported when switching to a generic formulation (Robinson, 2023).
Symptoms and side effects
Many symptoms can be managed by specific medications for Parkinson's disease, but some non-motor symptoms require additional treatment. Symptom onset is individualised and not everyone will experience all symptoms (Kobylecki, 2020).
Certain side effects, such as nausea and diarrhoea, are common when starting certain medications and patients need to be fully informed of these (including an estimated expected duration) to promote concordance (NINDS, 2023). Consider supplying ‘wait and see’ prescriptions for symptom relief where possible; e.g. domperidone for nausea (BNF, 2023).
Daytime sleepiness and sudden sleep can be a problem for patients, and some Parkinson's medications (such as levodopa and dopamine agonists) can exacerbate this (NINDS, 2023). Where this occurs the patient should be advised to stop driving and contact the DVLA, their car insurance company, (and workplace occupational therapy if this affects safety at work), if not already contacted. It may be worth starting treatment over a period when driving is not required, to determine the potential for this side effect, although side effects can occur at any point during treatment. Modafinil treatment can be considered to combat excessive daytime fatigue (NICE, 2017).
Orthostatic hypotension can occur in Parkinson's disease and can be exacerbated by dopaminergic medications and other concurrent medications (e.g. antihypertensives). Midodrine hydrochloride (first-line) or fludrocortisone acetate (second-line unlicensed indication) are potential treatments to mediate this where medication changes and non-clinical treatment has been ineffective (Kobylecki, 2020; BNF, 2023). Patients should be advised to contact specialist services if any new symptoms or untoward side effects occur so that they can be properly assessed. Acute infection such as chest infection or UTI and other conditions such as constipation, can exacerbate Parkinson's symptoms (as can psychological stress) (Umemura et al, 2014) and acute problems should be identified and treated in primary care before considering any changes to Parkinson's medication.
Conclusion
The treatment of Parkinson's is complex and prescribing medication is a highly specialised skill that should be undertaken by a health professional who regularly works with this patient group.
Medication side effects can have a huge impact on quality of life and medication concordance. The potential for common side effects and expectations for symptom control should be discussed with the patient and family members, if possible, at every opportunity, to manage expectations and promote trust between the patient and their clinical team. Where acute illness or stress has an impact on symptoms, this should be managed before changes to medication are made.
The NHS faces huge pressure at the current time, and clinicians should use credible alternatives for patient support, such as charitable organisations. These can often provide quick access to quality information, signpost to relevant support groups, and discuss general, non-patient-specific drug treatments and side effects.
Key Points
- Refer anyone with suspected Parkinson's disease, untreated, to a specialist
- Parkinson's disease symptoms can manifest and advance differently from person to person
- Consider acute illness as a potential cause of symptom changes
- Small changes to medication can often be helpful
- First-line treatment choice is dependent on several factors
CPD reflective questions
- Why should people with suspected Parkinson's disease be referred untreated to secondary care?
- What does the term ‘parkinsonism’ refer to?
- What needs to be considered for younger women who are diagnosed with Parkinson's?
- What management should be considered if a patient exhibits sudden psychiatric symptoms?
- Where can I find good-quality patient information for my patients?