Article

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.
CI - (c) The Authors. Developmental Medicine & Child Neurology (c) 2013 Mac Keith
Press.

Langue : ANGLAIS