Postmortem studies of deep brain stimulation for Parkinson's disease: a systematic review of the literature.

Deep brain stimulation (DBS), arguably the greatest therapeutic advancement in the treatment of Parkinson's disease since dopamine replacement therapy, is now routinely used. While the exact mechanisms by which DBS works still remain unknown, over the past three decades since it was first described, we have gained significant insight into several of the processes involved. Though often overlooked in this regard, increasing numbers of postmortem and autopsy studies are contributing significantly to our understanding. In this manuscript, we review the literature involving the pathological findings from autopsies in patients who have undergone deep brain stimulation surgeries for Parkinson's disease. The major results show that multiple stereotactic targeting methods can be accurate at placing leads in the desired nuclei that help with clinically effective results, that perioperative complications and inaccurate diagnosis as determined by autopsy can lead to suboptimal stimulation effect and that the normal long-term effects of chronic stimulation include fibrosis around the electrodes and a mild immune response. In addition, recent results suggest mechanisms by which DBS might be effective in Parkinson's disease i.e., through rescuing pathological changes in microvasculature and by promoting the proliferation of neural progenitor cells.