Deep brain stimulation (DBS) for movement disorders, in particular, Parkinson's disease and essential tremor, is a very well established treatment modality with proven efficacy in randomised controlled trials compared with best medical treatment.1 ,2

What is lacking is the answer to the question whether this is a sustained treatment effect over decades, as patients have a close to normal life expectancy, or whether DBS only works temporarily until the disease has progressed to a stage were DBS is rendered inefficacious. A positive question linked to this is whether DBS may even …