Secondary dystonia and choreoathetosis in children with dyskinetic cerebral palsy: from evaluation to a better understanding. .

Cerebral Palsy describes a group of permanent disorders of the development of movement and posture causing activity limitations, which are attributed to non-progressive disturbances that occurred in the developing fetal or infant brain. CP is classified into a spastic, dyskinetic and atactic group. Dyskinetic CP is further subdivided into secondary dystonia and choreoathetosis. In the past two decades, scientific research in CP has increased remarkably. However, most research has focused on the spastic type of CP. Much less is known regarding the evaluation and efficacy of treatment in patients with dyskinetic CP. Until now, there has been a lack of insight in the clinical features of dystonia and choreoathetosis, and to what extent they can be influenced by therapy. The scope of this doctoral project therefore was to contribute to the evaluation, characterization and understanding of secondary dystonia and choreoathetosis in children with dyskinetic CP. Given the paucity of available measurement tools for evaluation in this patient group, the first aim was to critically analyze the current scales and to develop a new clinical evaluation tool for this population (study 1, 2, 3). Secondly, this new clinical measurement scale was used to gain further insights into the two movement disorders in children with dyskinetic CP (study 4, 5). Dystonia and choreoathetosis usually coexist in dyskinetic CP. To evaluate dystonia and choreoathetosis in dyskinetic CP, reliable, valid and sensitive measurement scales are indispensable. To date there are three commonly used scales to measure dystonia of which one scale was developed for use in dyskinetic CP. In contrast, no measurement scale is available to evaluate choreoathetosis in dyskinetic CP. In study 1, we investigated the reliability and validity of the existing dystonia scales in children with dyskinetic CP. The results showed a moderate to good reliability for the three scales. However, measurement errors of the three scales were considered too high for clinical use. Also content analysis revealed that the three dystonia scales had limitations to capture the hallmarks of dystonia. To respond to the sensitivity limitations of the dystonia scales and the coexistence of dystonia and choreoathetosis, we developed the Dyskinesia Impairment Scale (DIS) in study 2. The DIS is subdivided in two subscales, one for dystonia and one for choreoathetosis. Both subscales evaluate duration and amplitude in 12 body regions including the eyes, mouth, neck, trunk, and limbs. For the limbs, a distinction is made between the proximal and distal region and between the right and left side. In hands of experienced raters in discriminating between dystonia and choreoathetosis, the results showed good to excellent reliability for both subscales and good concurrent validity for the dystonia subscale. This makes the scale promising for measuring dystonia and choreoathetosis in long-term follow up and evaluating the efficacy of continuing developing medical interventions such as oral medications, intrathecal baclofen, deep brain stimulation and botulinum toxin and in rehabilitation applications. Dystonia and choreoathetosis in dyskinetic CP are known as complex movement disorders. The discrimination between dystonia and choreoathetosis may be difficult because key elements like duration, speed and stereotypies of hyperkinetic movements are challenging to discriminate. Therefore, experience in discriminating between dystonia and choreoathetosis based on the operational definitions of these movement disorders, but also clinical expertise with the CP population may influence the reliability of scoring the DIS. In study 3 we included two groups of inexperienced raters; one group with clinical expertise in CP (senior physiotherapists) and another group without CP expertise (junior physiotherapists). The results of this study generally showed good reliability for the DIS in the inexperienced raters. There was no effect of clinical expertise for inexperienced raters. However, compared with the raters, experienced in discriminating between dystonia and choreoathetosis, reliability was lower with higher measurement errors. Therefore, a more comprehensive training for recognizing dyskinetic CP, based on the operational definitions is recommended. The second part of this doctoral project focused on gaining more insights in dystonia and choreoathetosis characteristics in children with dyskinetic CP with the use of the DIS. A better understanding of the clinical characteristics, also in relation to the functional severity and underlying brain lesions, is essential in providing more targeted therapy interventions. Study 4 aimed (1) to map dystonia and choreoathetosis across twelve body regions during voluntary asked activities and in rest (2) to assess whether these clinical characteristics would differ according to the severity levels of motor and communication classifications and (3) to examine their relationship with lesions in the thalamus and basal ganglia. For this study, 55 participants with dyskinetic CP (age range 6-22 years) were included. The results of this study showed simultaneous presence of dystonia and choreoathetosis, but with a higher dominance of dystonia. Secondly, higher scores of dystonia were clearly associated with more severe motor disability suggesting that dystonia, rather than choreoathetosis, has a larger impact on motor functions. Finally, pure thalamus and basal ganglia lesions seem to be associated with choreoathetosis but not with dystonia. These findings may serve as a basis for further research in a better understanding of dystonia and choreoathetosis and may help in delineating therapy interventions for dyskinetic CP. Dyskinetic CP is also known as the most disabling form of CP with generally severe functional impact However, to date, the relationship between the severity and distribution of both movement disorders and the activity abilities, the participation level and quality of life is unknown. This research question was addressed in study 5. A total of 54 participants with dyskinetic CP, aged between 5 and 22 years, were included. Dystonia and choreoathetosis were measured with the DIS. Activity was assessed by the Gross Motor Function Measurement (GMFM), the Functional Mobility Scale (FMS), the Jebsen-Taylor Test of Hand Function (JTT), and the Abilhand-Kids Questionnaire (ABIL-K). For social participation and quality of life, the Assessment of Life Habits Kids (LIFE-H) and the Quality of Life Questionnaire for children with CP (CP QOL) were used. The results showed a high relationship between dystonia and the activity scales and also, although to a lesser extent, with participation and quality of life scales. No relationship was found for choreoathetosis. These results indicate a high impact of dystonia at the level of activity, and may also affect participation and even quality of life. Taking into account these findings, interventions focusing on reducing dystonia may be most crucial. So far, medical interventions, such as ITB, DBS and BTX, mainly targeted on the treatment of dystonia. However, evidence supporting these interventions remains preliminary. Additionally, further investigation is needed to evaluation if reduction of dystonia and choreoathetosis following intervention also leads to improved functional abilities or enhanced participation and quality of life. This doctoral project has made a contribution to the evaluation of secondary dystonia and choreoathetosis and characterization and functional impact of these movement disorders. The DIS is the first scale that independently measures dystonia and choreoathetosis in dyskinetic cerebral palsy within a same score construct. The use of the scale provided us with new clinical insights in secondary dystonia and choreoathetosis in dyskinetic CP and is promising for evaluation of the efficacy of continuing developing medical interventions and in rehabilitation applications. The findings also serve as a basis for further research towards a better understanding of the pathophysiology of dystonia and choreoathetosis.

Jaar van publicatie:2013