[Apathy and deep brain stimulation in Parkinson's disease].

Apathy was defined by Marin as diminished motivation not attributable to diminished level of consciousness, cognitive impairment, or emotional distress. Up to 42% of Parkinson's disease patients could be concerned. It has a pejorative impact on quality of life and could be predictive of cognitive decline. It has been shown that deep brain stimulation in Parkinson's disease may induce apathy. It seems directly related to the stimulation target, i.e. the subthalamic nucleus, since such an effect has not been observed so far in thalamic and pallidal stimulation. It should certainly not make us question the remarkable effectiveness of subthalamic stimulation in Parkinson's disease patients, but encourages us to be very careful about operability criteria. We must, in this sense, improve identification of at risk patients, seeking a thoroughly diminished motivation, loss of interest or blunting affects.