What Proportion of Children and Young People Experience a Meaningful Improvement Following Deep Brain Stimulation for the Management of Dystonia? A Scoping Review and Meta-Analysis.

OBJECTIVES

Despite three decades of experience with Deep Brain Stimulation (DBS) in the management of motor disorders in children and young people (CYP), it remains unclear what proportion experience meaningful improvement. We aimed to establish i) the most common outcomes measures used for DBS in CYP, ii) evidence for minimally clinically important difference (MCID) for measures identified, and iii) the proportion of CYP achieving such MCID.

MATERIALS AND

METHODS

A scoping review was performed and reported following Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, identifying CYP (≤18 years) undergoing DBS for the management of their motor disorder. Evidence for MCID was explored for the five most common outcome measures.

RESULTS

Individual patient data were identified for 641 CYP across 157 studies. The most common outcome measures were the Burke-Fahn-Marsden Dystonia rating scale (BFMDRS) (539/641, 84.1%), the Barry-Albright Dystonia Scale (BADS) (71/641, 11.1%), the Gross Motor Function Measure-88 (GMFM-88) (63/641, 9.8%), the Canadian Occupational Performance Measure (COPM) (60/641, 9.4%), and the Unified Myoclonus Rating Scale (UMRS) (32/641, 5.0%). Whilst a 25% improvement in BFMDRS was often cited as the threshold for clinical response (achieved by 327/539, 60.7%), no evidence was identified to support this value as MCID. Considering a mild-to-moderate improvement in GMFM of 1.3%-24.5%, a significant change was seen in 25 of 62 CYP, a two-point change in COPM score was identified as MCID (achieved by 39/55, 70.9%). For the GMFM MCID appears to differ by both age and functional level and has not been determined for non-CP dystonia etiologies. No MCID could be identified for either the BADS or UMRS.

CONCLUSIONS

Whilst improvements are reported for most CYP undergoing DBS it remains uncertain for what proportion this translates into a clinically significant change. A consensus is required on what defines "response" to DBS to support counselling for CYP and families who may be considered for this intervention.