Reader response: Quality of life predicts outcome of deep brain stimulation in early Parkinson disease

I congratulate Schuepbach et al.¹ for their secondary analysis of data from the EARLYSTIM study;  however, their results were not unexpected and almost predicted by the very stringent selection criteria of the original study. Although other studies indicated that “off” time is a predictor of improvement after deep brain stimulation (DBS),² the analysis by Schuepbach et al.¹ did not include “off” time as a baseline prognosticator. It would have also been interesting for the authors to assess which 39-item Parkinson's Disease Questionnaire (PDQ-39) subdomains were driving the PDQ composite score postoperatively.³ It should also be noted that disease duration has a different impact during different stages of life because younger patients may have better compensatory mechanisms, being able to tolerate disease for a longer time, as opposed to older patients.⁴ Moreover, levodopa response as a predictor was examined in a narrow window because the original EARLYSTIM study included only excellent responders (>50%).⁵  Consequently, many questions remain unanswered regarding the applicability of the EARLYSTIM results in a patient population of a broader age and disease severity spectrum, not to mention target selection (i.e., pallidal stimulation). Nevertheless, the EARLYSTIM study still represents a global paradigm shift in the way we approach DBS.