Parkinson disease

and related disorders


Parkinson disease is a common disease of the brain (more than 200.000 patients in France). The disease starts generally after the age of 60. Its prevalence increases with age; it is over 4% after the age of 85.

Three clinical signs are characteristic:

  1. Stiffness of the muscles (« hypertonia »),
  2. Slowness of the movements and frozen aspect of the mimicry, called "akinesia"
  3. Tremor, especially of the fingers, hands, jaw, and feet, occurring at rest
Patients may experience other difficulties:

  • Depression
  • Sleep disorders
  • Constipation
  • Olfaction deficit.
  • ...

Parkinson syndromes

The symptoms and signs of Parkinson disease - the Parkinson syndrome- are found in disorders different from Parkinson disease. It may be difficult to make the diagnosis of the disease responsible for the "Parkinson syndrome". The post mortem study of the brain is still, in some cases, the only way of making a definite diagnosis. Idiopathic Parkinson disease, the most common cause of Parkinson syndrome, is characterized by the presence of a nearly specific alteration, the Lewy body, an abnormal structure found in some neurons and made of the accumulation of alpha-synuclein, a protein normally produced by the neurons but which has become insoluble for still unknown reasons. In other less common diseases, alpha-synuclein may accumulate in glia (i.e. non-neuronal cells of the brain) - the disease is called Multiple System Atrophy (MSA) - or it may be Tau protein -another protein that is normally produced by the neuron- that accumulates.Such an accumulation of Tau is found in several disorders, the most common being Progressive Supranuclear Palsy (PSP).

Whatever the change that is responsible for neuronal death, it is the alteration of a specific region of the brain, the substantia nigra, or of the target of its axons, that causes the Parkinson syndrome. The neurons of the substantia nigra synthesizes dopamine, a neuromediator. The lack of dopamine may be partially compensated - particularly by dopa, a medication that can be taken by mouth.

The cause of Parkinson syndrome remains generally unknown.

Idiopathic Parkinson disease generally occurs as a single case in a family - it is a "sporadic" disease. The cause is unknown: environmental factors have been incriminated, but have never been formally identified as "the" cause of Parkinson disease. There are rare cases of familial Parkinson disease due to mutations. Medications (such as neuroleptics), virus as the one responsible for the epidemic of encephalitis lethargica ("sleepy sickness") in 1915 may cause Parkinson syndromes.