Aim: The aim of this study was to examine the impact of dystonia aetiology and duration, contracture, and age at deep brain stimulation (DBS) surgery on outcome in a cohort of children with medically refractory, disabling primary, secondary‐static, or secondary‐progressive dystonias, including neurodegeneration with brain iron accumulation (NBIA).Method: Dystonia severity was assessed using the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS) motor score at baseline and 6 and 12 months postoperatively in a cohort of 70 consecutive children undergoing DBS between June 2005 and July 2011.Results: Two children (3%) received unilateral DBS for hemidystonia and were excluded and five (7%) developed infections requiring part‐DBS removal within 6 months, leaving 63 children (90%) undergoing bilateral DBS for follow‐up (34 males, 29 females; mean age at surgery for the whole group 10y 4mo, SD 4y 2mo, range 1–14y). Seventeen children were classified with primary dystonia: mean age 12 years 11 months, SD 4 years 6 months range 4 years 6 months to 17 years 3 months; 28 as having secondary‐static dystonia: mean age 10 years 2 months, SD 4 years 9 months (range 3y 3mo–20y); five as having secondary‐progressive dystonia: mean age 8 years 11 months, SD 3 years 9 months (range 5y 5mo–13y 1mo); and 13 as having NBIA dystonia: mean age 10 years 2 months, SD 3 years 11 months (range 1–14y). Children with primary dystonias demonstrated greater improvements in BFMDRS motor score than those in the other aetiological categories (Kruskal–Wallis test, p<0.001), which correlated negatively with dystonia duration and more strongly still against the ratio of dystonia duration normalized to age at surgery (DD/AS ratio) at 1 year (Spearman's rank correlation coefficient 0.4752 and −0.599 respectively). A similar significant negative correlation was found in the secondary‐static dystonia group between outcome at 1 year and DD/AS ratio (−0.461). Poorer outcome in secondary dystonia coincided with the absence of a period of normal motor development in comparison with the primary dystonia group. A significant improvement in BFMDRS motor score was seen in the NBIA group at 6, but not 12 months (Wilcoxon signed rank test p=0.028, p=0.85 respectively). No reduction in efficacy was seen in children with a musculoskeletal deformity at the time of surgery.Conclusion: Response to pallidal DBS in the treatment of dystonia declines with the proportion of life lived with dystonia in primary and secondary dystonia. Other intrinsic factors reduce the median magnitude of reduction in secondary dystonia after DBS. DBS should be offered early, preferably within 5 years of onset, to maximize benefits and reduce the childhood experience of dystonia, including musculoskeletal deformity. Other multidimensional assessments are required to understand how DBS improves the lives of children with dystonia.

Introduction and methods The impact of dystonia in childhood is poorly understood. We report our experience of referrals between 2005 and 2012. Results Of 294/315 assessable children, 15/294 had pure spasticity, leaving 279/294 with dystonia classified as primary (30/279: 10.7%); primary-plus (19/279: 6.8%) and secondary (230/279: 82.4%) dystonia, including heredodegenerative dystonia (29/279: 10.3%); 150/279 (53.7%) with cerebral palsy and 51/279 (18.2%) acquired brain injury. Definitive diagnoses were available in 222/294 (79.6%), but lower in primary/primary-plus compared with secondary groups (11/49 vs 211/230: Fisher's exact test p0.05); dystonia-onset age was 3 (0.5–7.0) for primary/primary-plus and 0.25 (0.08–0.8) in the secondary/CP groups. Dystonia duration at referral was 4.75 years (3.0–10.33) for primary/primary-plus groups and 7.83 (5.4–11) in the secondary group. The mean (interquartile range) proportion of life lived with dystonia, derived as dystonia duration normalised to age was 0.68 (0.31–0.96); 0.59 (0.35–0.8); 0.75 (0.62–0.95)and 0.9 (0.92–0.99) for primary, primary-plus, heredodegenerative and secondary-static dystonias respectively. Only 91/279 (32.6%) experienced a period of normal motor development. Carers perceived dystonia deterioration in 168/279 (60.2%), stabilisation in 88/279 (31.5%) and improvement in 23/279 (8.2%). Dystonia occurred in 26/225 (11.6%) siblings: 14/26 secondary and 5/26 heredodegenerative dystonia. Comorbidities were identified in 176/279 (63.1%) cases. Gross Motor Function Classification System (GMFCS) levels I–III were commoner in primary/primary-plus (37/49: 75%) compared with secondary/CP (29/230: 13%) cases, χ² p<0.0001). Discussion In this selective cohort, childhood dystonia is severe, presenting early before worsening without remission. Secondary dystonias spend a higher proportion of life living with dystonia and lower functional capacity. Despite referral bias, services offering neurosurgical interventions and health service planning agencies should understand the context and predicament of life with childhood dystonia.