Why Does Bilateral Subthalamic Stimulation Induced Cognitive Decline in Patients with Parkinson's Disease? (IN6-2.001)

Objective: To understand why some PD patients developed a cognitive decline in the year following STN-HFS. Background STN-HFS is efficient in alleviating parkinsonian motor signs. However, some patients developed a decline in cognitive function after surgery. Design/Methods: Between 02/1996 and 07/2009, 309 PD patients were operated for STN-HFS in the GHPS. Patients were evaluated before and one year after surgery with: 1) neuropsychological and 2) psychiatric tests, 3) parkinsonian disability scales (UPDRS parts I to VI). Precise location of stimulating contacts was obtained using an adjustable three-dimensional atlas of the basal ganglia. The stimulation parameters and levodopa equivalent dosage were reported. A voxel-based-morphometry was also performed on the pre-operative MRI of the patients. Postoperative cognitive decline was defined as a decrease more than 1 SD in the MDRS one year after surgery and/or MDRS Results: Two-hundred fifty-four patients were included in the final statistical analysis. Forty-five (21,5%) presented a decrease in the MDRS score more than 6 points (n=31) and/or a MDRS score under 130 (n=14). No statistical difference in the preoperative clinical characteristics was found between PD patients with vs without postoperative cognitive decline. Patients with postoperative cognitive decline presented a higher rate of postoperative confusion and/or psychiatric troubles. They showed a lower improvement in parkinsonian motor disability and activities of daily living with STN-HFS. The decrease in antiparkinsonian treatment and levodopa-induced complications was not different between the two patients groups. In patients with cognitive decline, the stimulating contacts were located more posteriorly and ventrally, and the frequency of stimulation was lower. Conclusions: STN-HFS may be deleterious for cognitive function, in particular when located in the more ventral part of the STN, thought to process cognitive and emotional information. Disclosure: Dr. Welter has nothing to disclose. Dr. Czernecki has nothing to disclose. Dr. Schupbach has received personal compensation for activities with Medtronic, Inc. and Lundbeck. Dr. Fernandez-Vidal has nothing to disclose. Dr. Karachi has nothing to disclose. Dr. Navarro has nothing to disclose. Dr. Cornu has nothing to disclose. Dr. Pidoux has nothing to disclose. Dr. Mallet has nothing to disclose. Dr. Dormont has nothing to disclose. Dr. Vidailhet has nothing to disclose. Dr. Grabli has nothing to disclose. Dr. Bonnet has nothing to disclose. Dr. Belaid has nothing to disclose. Dr. Houeto has nothing to disclose. Dr. Bardinet has nothing to disclose. Dr. Yelnik has nothing to disclose. Dr. Agid has nothing to disclose.