Parkinson's disease

Diagnosis and management of Parkinson’s disease Key points | Making the diagnosis | Natural history | Motor fluctuations Drug Management of Parkinson’s disease Summary points | Early Parkinson’s | Late Parkinson’s | Non-motor features References Issue 7 Contents

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Diagnosis and management of Parkinson’s Disease

Key points

1. The diagnosis of Parkinson’s disease is still based on careful history taking and clinical examination, despite ongoing advances in neuro-imaging and laboratory testing.
2. One of the first challenges is to differentiate between Parkinson’s disease and Parkinsonism – any group of nervous system disorders characterised by muscular rigidity, tremor and impaired motor control.
3. Management of Parkinson’s disease and co-existent health problems is a long journey, requiring a multidisciplinary team approach.
4. Initiation of drug treatment for early Parkinson’s disease is usually delayed until functional problems develop.
5. Levodopa is the drug of choice for Parkinson’s disease but approximately half of patients will experience fluctuations in motor control after 5 to 10 years of treatment.
6. Long-term management of Parkinson’s disease involves careful adjustment of medications and their doses along with other strategies such as education, exercise, speech therapy and nutrition.

Parkinson’s disease is one of the most common neurodegenerative diseases, with prevalence ranging from 100–180 per 100,000 population and an incidence of 4–20 cases per 100,000. There is a male to female predominance of 1.3:1. It typically presents in those over 60 years and the prevalence will increase with the ageing population.

While most cases of Parkinson’s disease are thought to be sporadic in onset, mutations in six nuclear genes have been associated with autosomal dominant or recessive Parkinson’s disease. A number of aetiologic factors have been considered including infections, toxins, head trauma, coffee and alcohol consumption. The strongest association is that non smokers are at greater risk of developing Parkinson’s disease.

The diagnosis of Parkinson’s disease is based upon careful history taking and examination, despite ongoing advances in neuro-imaging and laboratory testing. Computerised tomography (CT) and Magnetic Resonance Imaging show no specific changes but may help to exclude other conditions. Positron emission tomography and single photon emission CT may help in diagnosis but are not routinely available.

Ideally, patients should be managed jointly with GP, specialist and other health professionals including nurse specialist, physiotherapists, occupational therapists, social workers, speech-language therapists and the Parkinson’s Society field worker. Effective communication and team work are paramount for optimal management.

This is often a long journey which also requires the management of co-existent health problems and may culminate in end stage Parkinson’s disease and palliative care.

Making the Diagnosis

Getting the diagnosis correct underpins the best management of patients and a specialist opinion is usually helpful, ideally before starting any medications.

Careful history taking is essential and often provides a clear guide to the diagnosis. The duration of symptoms is important, as is any family history of either Parkinson’s disease or tremor.

The error rate in diagnosing idiopathic Parkinson’s disease has been reported as around 50% in general practice, 25% in general specialist clinics and 8% in specialised Parkinson’s disease clinics.¹

Differentiating Parkinson’s disease from Parkinsonism

One of the first challenges is differentiating Parkinson’s disease from Parkinsonism as the management is usually quite different.

Parkinsonism is any of a group of nervous system disorders with symptoms similar to Parkinson’s disease, characterised by muscular rigidity, tremor, and impaired motor control. There is often a specific cause, such as the use of certain drugs or frequent exposure to toxic chemicals.

It is essential to check for medications which interfere with dopamine release in the brain and hence cause Parkinsonism (neuroleptics, metoclopramide, prochlorperazine).

Features of Parkinson’s disease

Tremor: (Table 1) The most common presenting symptom is tremor, although the majority of those with tremor do not have Parkinson’s disease. Tremor in Parkinson’s disease usually presents as a unilateral, pill rolling hand tremor. It may affect other limbs and the head. Always query the diagnosis if tremor is absent.

The pattern of any tremor should be clarified, for example, whether it is worse on activity or at rest or if there are any relieving factors. Past medical history may indicate other diseases. A careful medication history is essential to exclude drug induced tremor.

Essential tremor is relatively common, affecting 0.4 to 4% of the population and approximately 2.5% of those over 60 years. It is often bilateral, progressive and not associated with other extrapyramidal signs.

Cerebellar tremor may be unilateral or bilateral depending upon its aetiology. It is worse on movement, often with a stuttering or saccadic character and worse at the beginning and end of movement. There may be other cerebellar signs including nystagmus and ataxia.

Table 1: Characteristics of Tremor

Rigidity and Bradykinesia: Bradykinesia and rigidity, micrographia, stiffness and slowness, may be features of other conditions including ageing, depression, dementia, arthropathies, polymayalgia rheumatica, and hypothyroidism, as well as Parkinson’s disease. At first presentation of Parkinson’s disease, patients may complain of a general slowing up and stiffness which can be attributed to ageing or osteoarthritis. There may be difficulties in turning over in bed, which may contribute to sleep disturbance. Speech may be slower, quieter and more monotonous. Patients may have expressionless faces and be less spontaneous.

The increased tone is classically present throughout movement (lead pipe) or has a cog-wheeling component to it. This can be thought of as the additive effects of tremor upon the lead pipe rigidity.

Gait disorder, postural changes and falls: These occur later in the disease course and if present early, should alert the clinician to an alternative diagnosis.

In Parkinson’s disease, the characteristic features usually begin with unilateral loss of arm swing and it is often helpful to watch the patient walk along a corridor. The gait is typically small-stepped and shuffling, described as festinating. The posture becomes stooped, and arms flexed. Patients turn en bloc, shuffling around on the spot. Postural stability becomes impaired and the risk of falling increases. Postural hypotension as a result of autonomic dysfunction and/or medication can contribute to falls.

Examination

Assessment should include:

Neurological assessment should include checking for red flags for alternative diagnoses.

Red Flags

There are some “red flags” (Table 2) which should always alert the clinician to an alternative diagnosis (Table 3).

Table 2: Red Flag alerting clinicians to an alternative diagnosis

Table 3: Parkinsonian Syndromes

Natural history

By the time symptoms of Parkinson’s disease appear, approximately 70–80% of the dopamine is lost from the substantia nigra indicating a substantial sub-clinical period. While dopamine is the primary neuro-transmitter involved in the pathology of Parkinson’s disease it is clear that others are involved including acetylcholine, noradrenaline, adenosine, glutamate and GABA.

The factors which determine prognosis and disease progression in Parkinson’s disease are not clearly established.

Initially, patients experience a prompt and even response to medication. Usually within two years, medication doses need to be increased and patients often take a combination of medications.

The lowest dose of medication needed should always be used. The progressive degeneration of dopamine terminals means the concentration of dopamine in the basal ganglia becomes more dependent upon plasma levels. These can fluctuate because of the 90 minute half life of levodopa and its unpredictable absorption. At this time, the consensus is that chronic administration of levodopa does not exacerbate the disease process.

Motor Fluctuations

Motor fluctuations occur in approximately half of patients after 5 to 10 years of treatment. These often are more severe in younger patients and are associated with the use of levodopa containing preparations. These include wearing off, dyskinesias and dystonias, and on-off episodes.

When the effect of levodopa wears off in less than four hours, this can initially be managed by increasing the dose of medication and/or shortening the dosing interval.

This can progress to on-off episodes (fluctuations between control and no control). Initially the pattern may be predictable with timing of medication and its effectiveness but it may become unpredictable. Patients may find themselves suddenly freezing, often when moving through doorways. Dyskinetic movements may occur typically when patients are in an “on” period. Dystonia, often painful, including dystonic inversion of the foot, may occur when the patient is either “on” or “off”

The treatment of such complications can be difficult and specialist help is usually required.

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