Introduction: Deep brain stimulation (DBS) of the globus pallidus interna (GPi) has been used in the treatment of intractable dystonias in the pediatric population and presently carries a humanitarian device exemption (HDE). While effective in the treatment of primary generalized dystonia, it has been more challenging to assess the initial and long term effects of DBS for secondary dystonia, especially in children. In addition to pain and loss of neurological function, children with severe and intractable secondary dystonia often face a degree of cognitive impairment not seen in primary dystonia. We have performed GPi DBS on three pediatric patients with intractable secondary dystonia refractory to medicines who experienced regression in functional neurological status and persistent pain .
Methods: Our patients were evaluated by developmental pediatric specialists and referred for evaluation of surgery because of painful secondary dystonia associated with decreases in motor function. In conjunction with a movement disorders neurologist, we obtained Investigational Review Board (IRB) approval for this study. For those receiving surgery, DBS leads are placed under general anesthesia into the posterior medial GPi with neuronavigation and CRW frame. We used micro-electrode recording to supplement anatomical localization of the targets. Electrodes were implanted in one or two stages, followed by separate surgeries for each pulse generator/battery. Patients are evaluated post-operatively using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and follow-up clinic visits. Also, we sought observations via interviews from parents and teachers of the children, of functional changes observed.
Results: We have documented sustained but fluctuating improvement in motor function and spasticity. Changes in electrode settings were managed by the movement disorder neurologist. There have been no complications to date. Parent and teacher observations and notes and the BFMDRS have been additional sources of information.
Conclusions: We believe DBS-GPi represents a useful treatment modality for carefully selected cases of severe intractable dystonia with neurological regression. The BFMDRS may not fully or adequately characterize the full benefit noted by patient, parents, and teachers.
Patient Care: Our research adds to an area of literature that is still young and growing. Deep brain stimulation (DBS) for primary (genetic) dystonia has been proven effective in a majority of cases, whereas secondary (acquired) dystonia is less reported upon. Additionally, the standard for evaluating all dystonia improvement is based up a scale that only takes functional movement into account. This is insufficient in cases of secondary dystonia because in these cases the patient often has some degree of cognitive impairment as well. Because the BFMDRS assesses only motor function, DBS may be more effective in treating secondary dystonia than previously described.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of deep brain stimulation in secondary dystonia, 2) Discuss, in small groups, whether the BFMDRS is an adequate measure of progress in secondary dystonia, 3) Identify an effective treatment strategy for intractabl secondary dystonia and how to assess clinical progress