Parkinson’s disease is a chronic, progressive neurological condition that currently has no cure. James Parkinson, whom the disease is named after, described the condition in a paper entitled An essay on the shaking palsy in 1817.¹ It affects around 9,000 people in Ireland, which equates to one in 500 of the population.² While Parkinson’s disease is a common condition in older people, one in 20 people who are diagnosed are under the age of 40.²

Parkinson’s disease results from the loss of the dopamine-containing cells in the substantia nigra section of the brain. Dopamine is linked to movement, thinking and emotion, hence the range of symptoms caused by a loss of dopamine. 

Parkinson’s disease is the most common form of Parkinsonism. This is an umbrella term for the clinical syndrome which involves slowness of movement plus at least one symptom of tremor, rigidity and/or problems with posture. Other causes of Parkinsonism include medical conditions such as strokes, Lewy-body dementia, supranuclear palsy and also medications. 

It is often not possible to distinguish between Parkinson’s disease and Parkinsonism caused by medication. However, Parkinsonism caused by medication usually presents with symptoms that are rapid in onset and affect both arms and legs. These patients often have no rigidity or resting tremor, but they have an ‘action’ tremor (a tremor on movement). Drugs that can possibly cause Parkinsonism include antipsychotics, anti-emetics and, more rarely, antidepressant medications.

Parkinson’s disease is usually slowly progressive but the prognosis varies between individuals. People with early-onset disease may have a later onset of motor (movement) complications and cognitive impairment. The mortality rate for older people with Parkinson’s disease is two to five times higher than for people of a similar age who do not have Parkinson’s disease.³

Suspecting Parkinson’s disease

Signs and symptoms of Parkinson’s disease include: 

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Bradykinesia – this is a slowness in initiation of movement with reductions in speed and ability to perform repetitive actions, such as finger or foot tapping

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Hypokinesia – this is an overall decreased movement, eg. reduced facial expression, arm swing while walking, or amount of eyelid blinking

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Difficulty with fine movements such as buttoning clothes and opening jars, or small, cramped handwriting (micrographia)

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Slow, shuffling, gait (rapid, small steps), or difficulty turning in bed

In addition, the person typically presents with at least one of the following motor signs of the disease: 

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Stiffness, rigidity with or without tremor felt when a limb is flexed by someone examining a patient

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Resting tremor – this tremor usually improves when the patient moves, with mental concentration, and during sleep. This may affect the thumb and index finger (‘pill-rolling’), the wrist, or the leg. It may also affect the lips, chin and jaw, but rarely involves the head, neck or voice

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Postural instability suggested by the ‘pull test’ – a tendency to stumble backwards after a sharp pull on both arms from the examiner.

These clinical features are usually unilateral in early disease, but may become bilateral in later disease.

Depression, anxiety, fatigue, reduced sense of smell, cognitive impairment, sleep disturbance and constipation may also be present in early disease and may precede the movement (motor) symptoms and signs described above.

Complications of Parkinson’s disease

People with Parkinson’s disease may develop a range of motor and non-motor complications.

Motor complications (often as a direct result of anti-parkinsonian medication) include immobility, slowness, communication difficulties, involuntary muscle movements, impairment of muscle movement, freezing of gait and falls. 

Two-thirds of people with Parkinson’s disease fall each year, and most people with Parkinson’s disease will eventually fall, but early onset of falls may indicate an alternative cause of Parkinsonism such as progressive supranuclear palsy. Falls are usually caused by many factors. These can include freezing of gait, postural instability, postural hypotension, cognitive impairment and environmental factors. 

Non-motor complications include depression, anxiety, apathy, psychosis, dementia, sleep disturbance, constipation, postural hypotension, dysphagia and weight loss, excessive salivation and sweating, bladder and sexual problems, and pain. These may be symptoms of Parkinson’s disease, complications, or side-effects of anti-parkinsonian medication. Most people are affected by non-motor problems as late complications of Parkinson’s disease.

Depression is very common in people with Parkinson’s disease, and may affect up to 50% of people. It is thought that depression is underdiagnosed as some clinical features of Parkinson’s disease, including reduced facial expression, sleep disturbance and cognitive impairment, overlap with symptoms of depression. Family or carers can provide valuable information to help make the diagnosis of depression.^4,5

The risk of dementia is two to six times higher in people with Parkinson’s disease than in healthy people.⁴ About one-third of people with Parkinson’s disease have some cognitive impairment at diagnosis, and it is estimated that 24-31% of people with later Parkinson’s disease have Parkinson’s disease dementia.^4,5 

Excessive daytime sleepiness and dozing affects 15-54% of people with Parkinson’s disease. Sleep disturbance is thought to be caused by degeneration of sleep regulation centres in the brainstem as well as physical complications such as being unable to turn over in bed, restless legs and vivid dreams related to anti-parkinsonian medication.^4,5 People who have sudden onset of sleep without awareness or warning signs should be advised not to drive and to think about avoiding other potential hazards in their daily lives, such as climbing ladders. 

Swallowing difficulties may affect up to 95% of people with Parkinson’s disease. Excessive salivation or drooling occurs in 70-80% of people with Parkinson’s disease and may be more common in men.^4,5 Referral to a speech and language therapist should be made promptly for full assessment and swallowing advice.

Up to 75% of people with Parkinson’s develop urinary symptoms. Nocturia, daytime urgency, frequency and urge incontinence are common. Alteration of antiparkinsonian medication or adding an antimuscarinic drug such as oxybutynin, may help symptoms.

Erectile dysfunction is more common in men with Parkinson’s (affecting 60-70% of men) than in age-matched controls (38%).⁴ Men with Parkinson’s disease may also experience sexual dissatisfaction and premature ejaculation. Dopaminergic drugs can also induce hypersexuality, even when there is erectile dysfunction. In women, difficulties with arousal, low sexual desire, and anorgasmia are common.^4,5

Pain occurs in up to 60% of people with Parkinson’s disease and often worsens during the course of the disease. Musculoskeletal pain, pain on movement and neuropathic pain are all common. Pain can be managed with simple analgesia or referral to physiotherapy or pain management services as appropriate. Pneumonia is a leading cause of death in the later stages.

Anti-parkinsonian medication 

Anti-parkinsonian medication such as levodopa is used to replace the dopamine lost in Parkinson’s disease and provide symptomatic relief. A dopa decarboxylase inhibitor such as co-beneldopa or co-careldopa is usually given with levodopa to reduce some of the potential side-effects caused by levodopa. Anti-emetics should be avoided as they can cause or exacerbate Parkinsonism.

The benefits of anti-parkinsonian medication can reduce over time, which can lead to rapid fluctuations in symptom relief due to changes in response to the treatment. This usually occurs after several years of use. 

Anti-parkinsonian medication should be initiated on the advice of a Parkinson’s disease specialist. A regular medication review should be undertaken and should include asking about problems with medication and any adverse effects. Adverse effects of anti-parkinsonian medication in addition to nausea include dizziness, drowsiness, hallucinations and abnormal movements.⁵

Referral and management plans

People with suspected Parkinson’s disease should be referred urgently, and untreated, to a specialist in movement disorders for confirmation of the diagnosis. In the UK, the NICE recommends that people with suspected mild Parkinson’s disease are seen within six weeks, and people presenting with later, complex disease are seen within two weeks. The aim of a quick referral is to reduce potential psychological distress caused by a delay in diagnosis. 

If Parkinson’s disease is suspected, but the person is taking a drug known to induce Parkinsonism, the drug should be reduced or stopped if possible. Referral should not be delayed to assess the response. 

A person with confirmed Parkinson’s disease should be managed by a specialist multidisciplinary team including a Parkinson’s disease specialist nurse who will monitor the person and help manage symptoms and complications.

Referral to speech and language therapy, physiotherapy, occupational therapy, adult social care, community nursing, continence and urology specialists, and psychology and mental health services, should be considered for each person affected. The needs of any carers should also be assessed, and the option of respite care discussed. For people with end-stage Parkinson’s disease, end-of-life discussions should be offered, including advance care plans and advance decisions. 

If the person drives at the time of diagnosis and if there is a change in their clinical condition, they should be advised to inform the Road Safety Authority and their car insurer. It is helpful to provide people with Parkinson’s and their family/carers with sources of information such as www.parkinsons.ie and www.hse.ie/eng/health/az/P/Parkinson’s-disease/

Catherine Lewis is a clinical author at Clarity Informatics, Nina Thirlway is a senior information analyst, and Dr Gerry Morrow is editor and medical director at Clarity Informatics

References

• Goetz CG. The history of Parkinson’s disease: early clinical descriptions and neurological therapies. Cold Spring Harb Perspect Med. 2011 Sep; 1(1):a008862. Available from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3234454/
• Parkinson’s Association of Ireland. Available at: http://www.parkinsons.ie/ [Accessed April 26, 2016]
• De Lau LM, Breteler MM. Epidemiology of Parkinson’s disease. Lancet Neurol. 2006 Jun; 5(6):525-35. 
• National Collaborating Centre for Chronic Conditions. Parkinson’s disease: national clinical guideline for diagnosis and management in primary and secondary care. Published 2006. Available from https://www.nice.org.uk/guidance/cg35/evidence/full-guideline-194930029 [Accessed April 26, 2016]
• SIGN. Diagnosis and pharmacological management of Parkinson’s disease. Published January 2010. Available from: http://www.sign.ac.uk/guidelines/fulltext/113/