Several cases of transient acute depression or manic symptoms are reported in the literature after bilateral subthalamic nucleus (STN) deep brain stimulation in patients with Parkinson's disease. Different hypothesis involve premorbid personality disorders, thymic past history or subthalamic nucleus.

We elaborate a one year prospective study to evaluate mood disorders frequency and physiological mechanisms of 20 Parkinsonian patients treated by bilateral STN stimulation. Evaluation consists of pre and post-operative psychiatric interview and scales assessing depression and mania.

At the present time, 18 patients have been operated, 17 have finished the program. Meaning age of patients: 63,1 years ± 7,3, with 5 women. No significant differences between men and women age, and duration of Parkinson disease (11,9 ± 4,4), were found (n=18).

One month before surgery, MADRS, Bech and Beck means (n=18) are respectively: 7,2 ± 4,2; 1,3 ± 1,6; 6,4 ± 3,5. At 3 months after surgery means (n=18) are: 3,9 ± 3,8; 1,1 ± 1,6; 3,1± 2,6. At 6months after surgery means (n=17) are: 6,7 ± 4,8 ;0,65 ± 1,1 ; 3,80 ± 2,6.

One patient, 70 years old, has presented a hypomanic-like episode post-operatively ; one other patient, 68 years old, presented a major anxio-depressive episode one month post-operatively (DSM-IV criteria). One patient, 53 years old, presented a moderated anxio-depressive episode, 6 months after surgery.

Data are still on analysed, but these cases draw our attention to the effects of STN stimulation on mood and behavioural disorders.