The study shows that more than one-half of all children with cerebral palsy in Norway have been treated with botulinum toxin A injections by the age of six. The proportion that received such treatment was highest among children with the spastic bilateral subtype and increased with higher degrees of functional impairment up to gross and fine motor function level III, while the proportion was markedly lower in children with the most pronounced degree of functional impairment (Level V). We found considerable variations in the proportion of children who received treatment as well as in dosages, muscle identification methods and use of sedation in the different habilitation centres in Norway.
One possible explanation for the large differences between the habilitation centres in terms of the proportion of children treated with botulinum toxin A might be that levels of functioning and other patient characteristics vary from one centre to another. However, the variation between the centres remained unchanged even when these factors were adjusted for.
The strength of the study lies in its use of data from the Cerebral Palsy Registry, which registers patients prospectively. Altogether 88 % of all children with cerebral palsy in Norway are included in the registry, and the population is thereby representative of all children with cerebral palsy in Norway (2). It is a weakness, however, that the registry does not specify which muscles have been treated with botulinum toxin A, treatment intervals, dosages and clinical effects of the treatment, nor any additional treatment such as the use of orthoses and physiotherapy/occupational therapy.
We found that the proportion of children who received injections of botulinum toxin A was comparable to what was found by a previous Norwegian study (8). The proportion of children treated with botulinum toxin A is high when compared to a recent Swedish study, which found that no more than approximately one-third of the children in a national follow-up programme had been treated at the age of 4–6 (13). We are not aware of any other studies that have investigated the frequency of botulinum toxin A treatment in a total population of children with cerebral palsy. We found, however, that a smaller proportion of the children with gross motor function level V had been treated in our study (49 %) when compared to what is suggested in the consensus report from 2009 (75–100 %) (5).
A total of 50–70 % of all children with cerebral palsy have hand impairments (14), but only 30 % of the children in our study had been injected with botulinum toxin in the upper extremities. This is disconcerting, since a systematic review from 2013 showed that such treatment in the upper extremities in combination with occupational therapy has the best documented effect (15).
Comorbidity and a higher total dose of botulinum toxin A may increase the risk of complications and adverse effects of the treatment, and children with severe functional impairment (gross motor function levels IV and V) and comorbidity appear to be at an increased risk of serious adverse effects (1, 6, 9). The explanation for why children with the poorest motor function levels were more rarely treated with botulinum toxin A could be a greater concern for serious adverse effects in this group (4, 5). The indication for treating children with the most serious impairments is normally to reduce pain and ease provision of care, and we may speculate as to whether children with the most severe forms of functional motor impairment are undertreated. Baclofen was most frequently administered to children with gross motor function level V, although relatively few had received such treatment.
Many treatment institutions used only palpation to identify muscles, even though the palpation method has been shown to have reduced accuracy. It is therefore recommended to use ultrasound as guidance during injections of botulinum toxin A in children (4, 5).
Our study cannot provide a definitive answer to the question of what constitutes the correct treatment level, and the consensus-based guidelines for treatment that have been published are largely experience-based and non-specific (4–6). A lack of evidence-based guidelines for botulinum toxin A treatment is the most likely explanation for the large variations in treatment practices that this study reveals.