Editing Deep brain stimulation (section)

====Methodological limitations ====
In trials on interventions, symptom scales such as the [[Unified Parkinson's Disease Rating Scale]] (UPDRS III) are typically used. These metrics measure motor function with a score from 0 to 108. Alternatively, the 39-item Parkinson's disease questionnaire (PDQ-39) has been utilized to measure disease specific quality of life with a score between 0 and 100. The effectiveness of an intervention is usually based on comparison of these scores in [[treatment and control groups]]. It has been pointed out that a statistically significant numerical difference in a scale or questionnaire does not necessarily translate to a clinically meaningful impact for the individual.<ref>{{cite journal |last1=Petersen |first1=JJ |last2=Juul |first2=S |last3=Jørgensen |first3=CK |last4=Gluud |first4=C |last5=Jakobsen |first5=JC |title=Deep brain stimulation for neurological disorders: a protocol for a systematic review with meta-analysis and Trial Sequential Analysis of randomised clinical trials. |journal=Systematic Reviews |date=13 October 2022 |volume=11 |issue=1 |page=218 |doi=10.1186/s13643-022-02095-z |doi-access=free |pmid=36229825|pmc=9558400 }}</ref> Beyond this, the scales can be subjective and susceptible to [[placebo effect]]s and physician bias.<ref name="Lancet 2004"/> The minimal important difference (MID) or minimal clinically important difference (MCID) has been suggested as a more pragmatic metric to standardize the clinical impact of an intervention, though it has not yet been widely adopted. It is defined as the smallest difference in symptom scores that an individual would consider clinically meaningful.<ref>{{cite journal |last1=Petersen |first1=JJ |last2=Juul |first2=S |last3=Kamp |first3=CB |last4=Løkkegaard |first4=A |last5=Jakobsen |first5=JC |title=We need to rethink outcomes in Parkinson's disease research. |journal=BMJ (Clinical Research Ed.) |date=18 October 2024 |volume=387 |pages=q2280 |doi=10.1136/bmj.q2280 |pmid=39424336}}</ref>