Neurodegeneration with brain iron accumulation encompasses a heterogeneous group 
of rare neurodegenerative disorders that are characterized by iron accumulation 
in the brain. Severe generalized dystonia is frequently a prominent symptom and 
can be very disabling, causing gait impairment, difficulty with speech and 
swallowing, pain and respiratory distress. Several case reports and one case 
series have been published concerning therapeutic outcome of pallidal deep brain 
stimulation in dystonia caused by neurodegeneration with brain iron 
degeneration, reporting mostly favourable outcomes. However, with case studies, 
there may be a reporting bias towards favourable outcome. Thus, we undertook 
this multi-centre retrospective study to gather worldwide experiences with 
bilateral pallidal deep brain stimulation in patients with neurodegeneration 
with brain iron accumulation. A total of 16 centres contributed 23 patients with 
confirmed neurodegeneration with brain iron accumulation and bilateral pallidal 
deep brain stimulation. Patient details including gender, age at onset, age at 
operation, genetic status, magnetic resonance imaging status, history and 
clinical findings were requested. Data on severity of dystonia (Burke Fahn 
Marsden Dystonia Rating Scale-Motor Scale, Barry Albright Dystonia Scale), 
disability (Burke Fahn Marsden Dystonia Rating Scale-Disability Scale), quality 
of life (subjective global rating from 1 to 10 obtained retrospectively from 
patient and caregiver) as well as data on supportive therapy, concurrent 
pharmacotherapy, stimulation settings, adverse events and side effects were 
collected. Data were collected once preoperatively and at 2-6 and 9-15 months 
postoperatively. The primary outcome measure was change in severity of dystonia. 
The mean improvement in severity of dystonia was 28.5% at 2-6 months and 25.7% 
at 9-15 months. At 9-15 months postoperatively, 66.7% of patients showed an 
improvement of 20% or more in severity of dystonia, and 31.3% showed an 
improvement of 20% or more in disability. Global quality of life ratings showed 
a median improvement of 83.3% at 9-15 months. Severity of dystonia 
preoperatively and disease duration predicted improvement in severity of 
dystonia at 2-6 months; this failed to reach significance at 9-15 months. The 
study confirms that dystonia in neurodegeneration with brain iron accumulation 
improves with bilateral pallidal deep brain stimulation, although this 
improvement is not as great as the benefit reported in patients with primary 
generalized dystonias or some other secondary dystonias. The patients with more 
severe dystonia seem to benefit more. A well-controlled, multi-centre 
prospective study is necessary to enable evidence-based therapeutic decisions 
and better predict therapeutic outcomes.