|Parkinson’s disease (PD) is a
chronic, progressive neurological disorder for which at present
there is no known cure. The core symptoms are tremor, rigidity (stiffness),
bradykinesia (slowness of movement) and balance difficulties (postural
It is the second most common neurodegenerative disease, affecting
more than 1 per 1000 people in Europe. It affects men and women
equally. Although PD is most common in the over 60’s, many
people are diagnosed in their 40’s and younger.
Parkinsonism is a term used to describe a neurological syndrome
characterised by tremor, rigidity and bradykinesia. Parkinsonism
can have many different causes; for example, side effects of drugs,
virus infections of the brain, little strokes or environmental
toxins. There are also other neurodegenerative disorders sometimes
referred to as Parkinson plus or atypical parkinsonian syndromes,
these include multiple system atrophy and progressive supranuclear
palsy (Steele-Richardson-Olszewski syndrome).
Idiopathic Parkinson’s disease
The term idiopathic means of ‘no known cause’. Idiopathic
Parkinson’s Disease or classical Parkinson’s disease,
as it is sometimes called, was first described by James Parkinson
in 1817 in “An Essay on the Shaking Palsy “.
Later, the French neurologist, Charcot, called the 'shaking palsy’
Parkinson’s disease in recognition of James Parkinson’s
Idiopathic PD is a disorder in which there is a degeneration
of the dopamine producing nerve cells in the substantia nigra,
deep within the brain. Dopamine is one of the chemical neurotransmitters
whose function is to transmit messages between nerve cells. There
are many different neurotransmitters and for the brain to function
smoothly all these neurotransmitters need to maintain a delicate
equilibrium. It is dopamine and acetylcholine, in particular,
that have to maintain their balance to ensure smooth controlled
movement of the body. Once 60- 80 % of the dopaminergic cells
cease to function normally, the motor symptoms of PD become evident.
It is not known what causes the loss of dopaminergic cells. Genetic
susceptibility is probably important in most cases. Damage to
nerve cells may be exacerbated as result of oxidative stress and
problems with the mitochondria (the batteries of the nerve cells)
are also thought to be important.
The symptoms of PD usually start on one side of the body (known
as unilateral) and can stay unilateral for several years. In most
people both sides will eventually be affected as the disease progresses.
The cardinal features are
- Resting tremor: This affects about 70 % of people with PD.
The tremor is most prominent while the patient is at rest and
usually affects the fingers and hands but may also affect the
legs, jaw and lips.
- Muscular rigidity: This ‘stiffness’ can be felt
when extremities are moved passively and is sometimes referred
to as ‘cogwheel’ or ‘lead-pipe rigidity’.
- Bradykinesia: Movements become slower and smaller as they
are repeated. The legs are not lifted as high while walking,
the sufferers facial expressions are reduced (‘hypomimia’),
hand writing becomes smaller and slower and patients have problems
in performing repeated movements, for example, repetitive finger-tapping.
In combination with muscular rigidity, bradykinesia leads to
a reduction of spontaneous and passive movements, for example,
passive swinging of the arms while walking.
- Postural instability: as the disease progresses, the small
movements we have to make in order to keep our balance aren’t
performed adequately. This makes it difficult for patients to
recover after stumbling and in advanced stages of Parkinson’s
during walking there may be start-hesitation, freezing and blocking
Other symptoms of PD
There is a range of symptoms that a patient may experience as
part of the disease or as the disease progresses. These include;
depression, quiet and soft speech, shuffling gait, tiredness,
pain, greasy skin, drooling of saliva, increased perspiration
and constipation. It is also now recognised that memory loss or
cognitive impairment can happen as the disease progresses, especially
over the age of 65 years.
Diagnosis rests on a full clinical examination. Bradykinesia
plus either rigidity or tremor should be present before a diagnosis
of PD is made. Some investigations and tests may be done to exclude
other neurological conditions.
Management of PD
Optimum management of PD relies on a continuum of care from a
multi-disciplinary team of health care professionals. Ideally,
a specialist nurse, physiotherapist, speech and language therapist
and occupational therapist should all be involved along with a
neurologist or physician with special interest in PD.
There is no cure for PD but there are treatments that help to
control the symptoms.
Each person can have a different combination of symptoms and medications
are tailored to each individuals need. The main aim of the medications
is to restore the deficiency of dopamine in the brain and re-establish
normal function in the brain circuits. Patients often need to
take a combination of medications which may include:
L-Dopa is a natural precursor of Dopamine. It enters into the
brain where it is transformed into Dopamine. L-Dopa is the most
effective available drug. However, after long-term use complications
can occur including motor fluctuations (on-off effects) and dyskinesias
(abnormal involuntary movements), especially if high doses are
taken over many years.
Dopamine agonists trick the brain into thinking they are dopamine.
Side effects include, nausea and vomiting during the up-titration
of the drug, postural hypotension (lowering of blood pressure
upon standing) and psychiatric side effects might occur. These
drugs when used alone have a much lower propensity to cause dyskinesias
than L-Dopa. However, they are less effective.
Apomorphine is a dopamine agonist that is given via subcutaneous
injection or infusion. It is used when oral medications have become
less effective and motor fluctuations and dyskinesias are prominent.
Anticholinergics have a mild antiparkinsonian effect and are most
useful in young patients with tremor and dystonia.
This is a mild antiparkinsonian drug which can also reduce involuntary
movements provoked by L-Dopa.
A mild drug which can mildly potentiate L-Dopa
These are drugs which may mildly improve the efficacy of L-Dopa
There is interest and research in the use of Vitamin E and Co-Enzyme
Q10 for their neuroprotective potential.
Surgical treatment may be considered for patients whose PD symptoms
cannot be adequately controlled with medical management. The most
effective available approach involves stimulation of both subthalamic
nuclei with implanted pacemakers.
Research is underway in neurotransplantation of foetal substantia
nigra, transplantation of nerve growth factors for promoting recovery
of nigral neurones and gene therapy.
There is no cure for Parkinson’s disease. The medications
and surgical treatments currently available do help control the
symptoms, but do not halt the progression of the disease. Medical
research is dedicated to finding the cause, cure and ways to improve
treatments and to prevent Parkinson’s disease. This requires
the participation of patients in clinical trials and continued
funding from medical, social and private sources for research
to take place.