Neuromodulation for children with cerebral palsy
Cerebral palsy (CP) includes a heterogeneous group of developmental disorders often characterized by dystonia and choreoathetosis (dyskinetic CP) Dyskinetic CP is the most frequent cause of acquired dystonia in childhood, leading to severe physical disability. The management of dyskinetic CP is particularly challenging since pharmacological treatment is often unsatisfactory due to both modest clinical efficacy and frequent medication related side effects. In isolated dystonia, surgical treatment with deep brain stimulation (DBS) of the globus pallidus internus has emerged as a very effective strategy, but its benefits for dyskinetic CP are still debated. In this timely review by Sanger, the state of the art of DBS for dyskinetic CP is nicely and concisely described. Overall, DBS seems to be less effective and with more variable outcomes in dyskinetic CP compared to isolated, idiopathic, or monogenetic dystonia. However, available data about DBS in children with dyskinetic CP are still scarce and mostly from retrospective small case series with short term follow up. A recent review has suggested that DBS could possibly be effective for dystonia in dyskinetic CP based on the positive results of 6 out of 12 class III studies (level C) There are likely several reasons why clinical evidence for DBS cannot advance in dyskinetic CP. First, the neurophysiological bases of dyskinetic CP are still unclear. This unsolved issue also impacts the choice of possible better targets for DBS therapy, especially considering the frequent presence of structural brain lesions. Indeed, there is some evidence suggesting that other targets besides the globus pallidus internus can be a better choice in CP. Furthermore, it can be challenging to assess positive motor outcomes in patients with associated severe spasticity, ataxia, and fixed skeletal deformities. Standardized, age related, and sensitive assessment tools able to capture subtle motor changes after DBS in children with dyskinetic CP are lacking. For example, the most commonly used scale for dystonia, the Burke Fahn Marsden Dystonia Rating Scale, was developed for adults. The current scales used to score dystonia do not fit well with the dyskinetic CP profile and cannot provide the real subjective and objective awareness of clinical benefit after DBS. Moreover, CP includes a heterogeneous group of developmental disorders that prevents the development of strict established selection criteria for surgery, besides the major criterion of mobile dystonia impacting quality of life. Indeed, there are no clear predictive factors for DBS outcome in dyskinetic CP compared to isolated dystonia, where age and duration of dystonia at the time of surgery are strictly correlated with clinical improvement. To move forward, larger prospective studies with longterm follow up that use suitable motor and disability evaluation tools in children with dyskinetic CP are needed. The impact of DBS on neuropsychological and neuropsychiatric aspects, as well as quality of life, should also be better evaluated in children. DBS should probably be offered earlier in children with dyskinetic CP to reduce maladaptive neuroplasticity and prevent skeletal deformities. Current collaborative efforts to share data from centres performing DBS in children should be powered. In the future, technological advances in magnetic resonance imaging based targeting, the search for new targets, and new stimulation strategies aimed at optimizing parameters settings, like adaptive stimulation, will improve DBS outcomes in children with dyskinetic CP.
Developmental medicine and child neurology