Article

Behavioral changes in Parkinson's disease are complex and their
pathophysiology is not yet fully understood. The dopaminergic system seems to
play a major role and most of the behavioral disorders in Parkinson's disease can
be classified into either hypodopaminergic if related to the disease itself or
hyperdopaminergic if related to dopaminergic treatment. Subthalamic stimulation, which enables withdrawal of dopaminergic medication at
an advanced stage in the disease, provides a model for the study of certain
nonmotor, dopamine-sensitive symptoms. Such a study has shown that apathy, which
is the most frequent behavioral problem in Parkinson's disease, is part of a much
broader hypodopaminergic behavioral syndrome which also includes anxiety and
depression. Nonmotor fluctuations--essential fluctuations in the patient's
psychological state--are an expression of mesolimbic denervation, as shown in
positron emission tomography. Drug-induced sensitization of the denervated
mesolimbic system accounts for hyperdopaminergic behavioral problems that
encompass impulse control disorders that can be alternatively classified as
behavioral addictions. The association of impulse control disorders and addiction
to the dopaminergic medication has been called dopamine dysregulation syndrome.
While L-dopa is the most effective treatment for motor symptoms, dopamine
agonists are more effective in improving the nonmotor levodopa-sensitive
symptoms. On the other hand, L-dopa induces more motor complications and dopamine
agonist more behavioral side effects. There is increasing data and awareness that
patients' quality of life appears to be dictated by hypo- and hyperdopaminergic
psychological symptoms stemming from mesolimbic denervation and dopaminergic
treatment rather than by motor symptoms and motor complications related to
nigrostriatal denervation and dopaminergic treatment. PERSPECTIVES: Better
management requires knowledge of the clinical syndromes of hyper- and
hypodopaminergic behaviors and nonmotor fluctuations, a better understanding of
their underlying mechanisms and the development of new evaluation tools for these
nonmotor symptoms. CONCLUSIONS: The neurologist who strives to gain mastery of
dopaminergic treatment needs to fine tune the dosage of levodopa and dopamine
agonists on an individual basis, depending on the presence of motor and nonmotor
signs respectively.
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Langue : FRANCAIS