Objective evaluation of motor outcomes in deep brain stimulation of the STN: Beyond patient's self-report
Résumé
Over the last decades, deep brain stimulation (DBS) of the subthalamic nucleus (STN) has developed as a surgical alternative to levodopa medication in Parkinson's disease (PD). DBS is also used as a treatment for essential tremor or dystonia and is now moving toward psychiatric disorders (depression, obsessive compulsive disorder). New approaches for Parkinson disease, including gene therapy and multiple target DBS, are likely to develop in the future and raise issues concerning the objective evaluation of treatment outcomes. Outcome following DBS is typically assessed using the Unified Parkinson Disease Rating Scale (UPDRS-III) and the Parkinson Disease Quality of Life Measure (PDQ-39). Although efficient and widely used these measures focuses on overt, and often self-reported, aspects of motor behavior such as rigidity, tremor, fine motor control, posture, locomotion and bradykinesia. Starting from published results in the field of motor control and rehabilitation we propose that evaluation should be made more objective by using known principles of motor behavior to assess the current state of the patient's motor system. Results from a follow up study on a group of 7 patients with Parkinson disease treated with DBS of the STN are used to illustrate the power of the motor principles approach for detecting changes in fine motor control. We conclude that objective motor assessment could be used both for precisely estimating the outcomes of DBS of the STN and for finding the best site location for the electrodes during surgery.