Parkinson's Disease
   
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 instability).
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

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 remarkable work.

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 and falls.

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
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.

Drugs
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:
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:
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:
Anticholinergics have a mild antiparkinsonian effect and are most useful in young patients with tremor and dystonia.

Amantadine:
This is a mild antiparkinsonian drug which can also reduce involuntary movements provoked by L-Dopa.

Selegiline:
A mild drug which can mildly potentiate L-Dopa

COMT-Inhibitors:
These are drugs which may mildly improve the efficacy of L-Dopa e.g. Entacapone

Dietary supplements:
There is interest and research in the use of Vitamin E and Co-Enzyme Q10 for their neuroprotective potential.

Surgery
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.

Medical research
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.

   

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