There has been much recent media interest in Parkinson's disease due to the celebrity status of one of the latest sufferers - American film actor Michael J. Fox

What is it?
Parkinson's disease (shaking palsy) is a slowly progressive disease of the brain, which is characterised by shaking and difficulty with co-ordination, walking and movement, and was first described in England by James Parkinson in 1817.

The disease is associated with damage to the part of the brain that controls muscle movement, and it is usually slowly progressive, affecting one or both sides of the body. It may involve speech difficulties, an overall mental deterioration, dementia and changes to emotional responses. Some people with Parkinson's disease also become severely depressed - although early loss of mental capacities is uncommon.

Who gets it?
Parkinson's disease usually only occurs in adults - it is very rare in children - and in the UK it can affect approximately two out of 1,000 people, but because the disease is not contagious and does not need to be reported, true statistics are not really known.

Sex incidence is about equal, although some reports indicate that it occurs slightly more often in men. Whilst ten per cent of those who are affected are under 45 years at the onset of the disease, it does occasionally occur in younger adults, but it is rare under 30 years of age. Both the incidence and the prevalence increase with age, with the latter rising to one per cent in those over 60. It is one of the most common neurological disorders of the elderly.

The diagnosis has to be made clinically as there is as yet no diagnostic test for Parkinson's disease. Some investigation may be necessary, in certain suspected cases, in order to exclude other causes of 'Parkinsonism' - if there are evident features of the disease.

Interestingly, Parkinson's disease is apparently less common in cigarette smokers.

What causes it?
The exact reason for specific cells of the brain to deteriorate is unknown, and no regular genetic influences had been identified until recent work on twins suggested quite strongly that a genetic influence may, in fact, be greater than was previously thought. In some cases the disease occurs with extraordinarily high incidence in families, especially if it affects young people, and a defective gene has been demonstrated.

It is known that in Parkinson's disease there is a progressive deterioration of certain nerve cells in a specific area of the brain, and this can be demonstrated by the use of modern imaging techniques. These cells are responsible for producing a particular chemical - dopamine. This is one in a chain of chemicals necessary for the proper conduction of the nerve impulses within this area of the brain. If there is a disturbance, then there is inefficient transmission of messages in this area, which is responsible for muscle movements. Consequently, loss of various aspects of muscle function occurs. The exact reason that these specific cells of the brain deteriorate is unknown.

There are other conditions that can produce Parkinson-like features (secondary Parkinsonism):

• Some cases of the 'disease' have been thought to be associated with an exposure to various chemical toxicants, beginning in childhood and continuing throughout life, which are found in the environment.
• Other exposures to such chemicals as pesticides and certain wood preservatives have been researched and recorded as a possible link.
• There are also certain prescribed medications, which, as a side effect, can cause Parkinsonism features; these clear as soon as the medication is discontinued.

What are the symptoms?
There are very many symptoms, and they will not all be found in every person affected. These will include:

• Muscle rigidity and stiffness, difficulty with bending of limbs
• An unstable, stooped or bent-over posture
• General loss of balance
• Variable changes in walking pattern, with characteristic features
• Shaking, tremors and fixed facial expressions
• Slow speech with general speech changes

What is the treatment?The treatment for Parkinson's disease involves not only the use of drugs - which is the mainstay of treatment for most patients - but also the involvement of many other disciplines: nursing, speech, occupational and physiotherapies and diet. More recently, advances in brain surgery have been made so that on occasion a number of surgical procedures can also be considered for some people.

Drugs: The various drugs used for treatment are of differing actions; some are more useful in situations where a particular symptom dominates. Many of them can have side effects in some people, side effects that have features so like Parkinson's disease itself that they have to be discontinued. Treatment management and stabilisation can often, therefore, be very difficult and complicated.

Surgery: It is the advancements in surgical techniques that are starting to offer patients a better chance of a successful treatment. Specific areas of the brain can be approached by a variety of surgical interventions: implantation of electrodes for stimulation of certain areas as needed; electrode destruction of trouble-causing cells in the brain (stereotactic surgery); and more recently, brain tissue transplants have produced encouraging results (where genetically engineered cells can be placed in the brain in order to supply the 'missing' chemicals), but this is really still in the experimental stages.

For further information and help sources on Parkinson's disease, visit www.parkinsons.org.uk