Concept of Hypodopaminergic and Hyperdopaminergic Behavioral Disorders in Patients with Parkinson's Disease

A dysbalance within the dopaminergic system (hypodopaminergic and hyperdopaminergic dysregulation) can cause severe behavioral disorders in patients with Parkinson's disease affecting patient's daily life. Hypodopaminergic states are present in a dopamine withdrawal syndrome, a dopamine agonist withdrawal syndrome and after deep brain stimulation of the subthalamic nucleus, when medication can be reduced dramatically. These syndromes include signs and symptoms of apathy, a lack of energy, a lack of spontaneity, psychic signs and symptoms such as depression and anhedonia and vegetative symptoms like orthostatic dysregulation. A hyperdopaminergic dysbalance can be caused by a dopamine replacement therapy especially by dopamine agonists and the dopamine dysregulation syndrome. Impulse control disorders such as hypersexuality, binge eating, compulsive shopping and pathological gambling and punding are symptoms of a hyperdopaminergic behavioral disorder. Since controlled studies to treat these behavioral disorders are rare the treatment concept must focus the individual problems of a patient. Both, the hypodopaminergic and the hyperdopaminergic behavioral disorder seem to be caused by a dysfunction of the mesolimbic dopaminergic reward system.