A 7-year observation of the effect of subthalamic deep brain stimulation on impulse control disorder in patients with Parkinson's disease

Introduction: Previous studies have reported improvement of impulse control disorders (ICDs) after subthalamic nucleus (STN) deep brain stimulation (DBS) as well as some de novo ICDs. However, it is not clear how STN DBS changes ICDs in the long-term. Methods materials: Eighty-nine patients with Parkinson's disease (PD) who had received a bilateral STN DBS from 2005 to 2009 and were included in our previous study were followed for 7 years with the modified Minnesota Impulsive Disorders Interview (mMIDI). Their mMIDI scores, medication, and frontal function tests measured preoperatively and at 1 and 7 years postoperatively were compared. Results: A total of 61 patients were analyzed after excluding 10 and 18 patients due to death and lost to follow-up, respectively. The numbers of the patients with an ICD at each point were 8, 10, and 7, respectively. All preoperative ICDs disappeared after DBS. De novo ICDs within 1 year after DBS disappeared except for 1 patient. Six of the seven patients, who reported ICDs 7 years after the DBS developed that ICD between 1 and 7 years. Their total levodopa equivalent daily dose (LEDD) and dopamine agonist dose were not higher compared to the other 54 patients without ICDs. There was no correlation with the frontal lobe dysfunction and the electrode position in the subthalamus. Conclusion: STN DBS improves baseline ICDs and results in the development of “transient” de novo ICDs in the short-term. In addition, there is a unique group of the patients who develop ICDs a long time after DBS.