Deep brain stimulation for neurological disorders: a protocol for a systematic review with meta-analysis and Trial Sequential Analysis of randomised clinical trials.

Background: Deep brain stimulation has been used since the 1980s for neurological disorders and the USA and Europe have now approved it for Parkinson's disease, essential tremor, dystonia, and epilepsy. Previous reviews have assessed the effects of deep brain stimulation on different neurological disorders. These reviews all had methodological limitations.
Methods: This is a protocol for a systematic review based on searches of major medical databases (e.g. MEDLINE, EMBASE, CENTRAL) and clinical trial registries. Two review authors will independently extract data and conduct risk of bias assessment. We will include published and unpublished randomised clinical trial comparing deep brain stimulation versus no intervention, usual care, sham stimulation, medical treatment, or resective surgery for Parkinson's disease, essential tremor, dystonia, or epilepsy. The effects of deep brain stimulation will be analysed separately for each of the different diagnoses. Primary outcomes will be all-cause mortality, disease-specific symptoms, and serious adverse events. Secondary outcomes will be quality of life, depressive symptoms, executive functioning, level of functioning, and non-serious adverse events. Data will be analysed using fixed-effect and random-effects meta-analyses and Trial Sequential Analysis. Risk of bias will be assessed with the Cochrane Risk of Bias tool-version 2, an eight-step procedure to assess if the thresholds for clinical significance are crossed, and the certainty of the evidence will be assessed by Grading of Recommendations, Assessment, Development and Evaluations (GRADE).
Discussion: Deep brain stimulation is increasingly being used for different neurological diseases, and the effects are unclear based on previous evidence. There is a need for a comprehensive systematic review of the current evidence. This review will provide the necessary background for weighing the benefits against the harms when assessing deep brain stimulation as intervention for individual neurological disorders.
Systematic Review Registration: PROSPERO 306,556.
(© 2022. The Author(s).)