Parkinson's – the disease that makes us tremble

What is Parkinson's disease?

Parkinson's is a slowly progressing neurodegenerative disease that causes the destruction of a specific population of neurons, namely dopaminergic neurons in the substantia nigra of the brain. These neurotransmitters are essential for controlling the body's movements and in particular, automatic movements.

It is the second most common neurodegenerative disease in France after Alzheimer's disease. Moreover, it is a major cause of disability in elderly patients.

Parkinson's disease is extremely rare before the age of 45. It mainly affects older patients, peaking around the age of 70 with 1% of over-65s suffering from the illness. In total, between 100,000 and 120,000 people are affected in France and approximately 8,000 new cases are reported every year.  What's more, the disease is becoming increasingly prevalent due to the ageing population.

Causes

Although the exact causes of neurodegeneration are unclear, age has been identified as the main risk factor. Genetic and environmental factors appear to play a part in the gradual loss of dopaminergic neurons.

Parkinson's disease is therefore not generally a hereditary disease, although there is a 5% incidence of genetic forms. In terms of environmental risk factors, a link with early or prolonged exposure to chemical pollutants or pesticides including herbicides and insecticides has been clearly established.

MPTP, a contaminant drug sometimes found in heroin, can suddenly cause a serious and irreversible form of Parkinson's disease. Carbon monoxide or manganese poisoning can also have the same effect.

Parkinson

Symptoms

It is important to note that by the time the symptoms occur, the disease has already progressed 5 to 10 years on average.

Parkinson's disease is diagnosed on the basis of three main motor symptoms. These will not all necessarily occur at the same time and may vary in intensity. They remain asymmetrical for a long period, affecting only one side of the body. The symptoms are:

  • Akinesia, which is the most common sign, whereby patients perform and coordinate movements more slowly. It affects all everyday activities including walking. Akinesia is perfectly treatable and generally becomes a phenomenon that fluctuates over the course of the day as treatments are administered. Physiotherapy plays an important part in managing the condition.
  • Hypertonia or excessive muscle rigidity. This can affect all the body's muscles including the spinal muscles. In particular, it is responsible for patients adopting a forward-leaning posture.
  • Tremors mainly affecting the hands and arms that occur at rest and cease when the patient starts to move. They may be intermittent and do not automatically occur since approximately 30% of patients do not suffer from them. Shaking can be effectively corrected by treatments but may reappear in emotional situations.

Other symptoms may also occur depending on the patient:

  • anxiety and depression;
  • difficulty swallowing;
  • excessive salivation;
  • small, very cramped handwriting (micrographia), due to a loss of dexterity;
  • quaking, expressionless voice and problems with enunciation;
  • lack of facial expression and reduced or no blinking;
  • dandruff and oily facial skin;
  • urinary incontinence;
  • confusion, memory loss and other quite severe mental disorders occurring relatively late in the progression of the disease;
  • difficulty changing positions e.g. it may be difficult for patients to get out of their bed or armchair. And in some cases, patients lose their ability to move.

Treatments

With the treatments that are currently available, it is possible to alleviate the symptoms and slow the progression of the disease quite effectively. Patients can live with Parkinson's for several years.

Although no current treatment is capable of curing Parkinson's disease, it is possible to alleviate the symptoms using drugs and adopting a number of lifestyle-related measures.

Medicinal treatments are available. However, patients should also adapt their lifestyle to improve their quality of life:

  • Staying active
  • Planning in periods of relaxation
  • Preventing falls

Medicines can compensate for patients' dopamine deficiency:

  • Levodopa or L-dopa is a dopamine precursor that is converted into dopamine when administered
  • Dopamine agonists replicate the effects of dopamine
  • Monoamine-oxidase B (MAO-B) inhibitors such as selegiline and rasagiline may be prescribed from the onset of the disease
  • Anticholinergics (benzotropine, trihexyphenidyl, etc.) help limit tremors in some patients by restoring the balance between dopamine and acetylcholine in the brain.
  • Catechol-O-methyltransferase (COMT) inhibitors prolong the effects of carbidopa-levodopa therapy by blocking the enzyme that breaks down levodopa
  • Amantadine, an antiviral drug originally developed for influenza, has proved beneficial for people suffering from Parkinson's disease

As with any other treatment, strict adherence is essential. Pill dispensers that are appropriate for patients in terms of their shape, capacity, size and ease-of-opening are available from Pilbox, the French brand that has devoted over 20 years to therapeutic observance.

Research

Although knowledge of what causes Parkinson's disease remains limited, advances in research have enabled treatments to be considerably improved over the past two decades. Parkinson's is the most widely studied cerebral syndrome in France, where research on the disease is very active.

One of the major challenges currently facing researchers is to identify ways of detecting the disease early since, as mentioned above, the symptoms only appear when most of the neurons are destroyed. Through earlier diagnosis, it should be possible to eventually slow or even halt the progression of the disease well before the stage at which it is currently detected.

Sources: inserm.fr, passeportsante.net, franceparkinson.fr