## 4 Discussion  
This study aimed to develop the DIMS, a new tool to measure presence and severity of both dystonia and choreoathetosis during powered mobility tasks in DCP. The DIMS is an adapted standardized protocol of the DIS which is a reliable and valid tool to measure presence and severity of dystonia and choreoathetosis during requested but voluntary activities and rest postures. The outcomes of this study indicate that DIMS is a reliable and valid measurement tool to determine presence and severity of dystonia and choreoathetosis during powered mobility. A moderately high to good interrater reliability was found for the total score of the DIMS, the DIMS-D and the DIMS-CA with correlation coefficients of 0.87, 0.68 and 0.79 respectively. Good interrater reliability was found for the total DIMS duration factor and amplitude factor with coefficients of 0.83 and 0.73. In addition, internal consistency scores were moderately high to good. Finally, concurrent validity showed during mobility tasks significant correlations with rest postures in the arm region, and with voluntarily, requested activity in the neck region. Interrater reliability scores are good, in particular for DIMS total and DIMS-CA. The reliability of DIMS total is in line with both the interrater reliability of junior and senior physiotherapists [15], implying that the DIMS can be reliably used in the future by all clinicians, regardless of their work experience. Interrater reliability scores of DIMS-D duration are relatively lower as is in line with previous literature [14; 15]. Visual inspection of the raw data showed a much lower variability in the scores of the duration factor than the scores of the amplitude factor. In addition, low DIMS-D duration scores primarily occur in proximal arm regions, while scores in neck and distal arm regions are still moderate to moderately high. This might be because the visibility of the proximal arms is slightly lower due to the sitting position of the participants while driving the wheelchair in comparison to the distal arm region and neck region. Similarly, this may explain why scoring the duration of dystonia for the proximal arms is more difficult than scoring its amplitude, which is clinically easier to see and evaluate [14]. Interestingly, for the proximal arm regions, an excellent interrater reliability was found for the duration factor of the DIMS-CA. This is likely due to the hyperkinetic nature of choreoathetosis, which is easier to observe than the hypertonic nature of dystonia [8]. The summation of both factors revealed a good interrater reliability for the DIS-D region scores, implying a reliable measure of dystonia for both voluntary and overflow movements during powered mobility. In this respect, higher scores for the duration factor as opposed to the amplitude factor were obtained for the DIMS-CA subscale, which is in line with previous research [14; 15]. The good to excellent interrater reliability of the DIMS-CA duration and amplitude factors shows that presence and severity of choreoathetosis can be reliably measured during powered mobility. The current study of the DIMS is the first to assess test-retest reliability in measuring presence and severity of movement disorders in DCP. The test-retest reliability of the total DIMS score, DIMS-D subscale and DIMS-CA subscale was moderate to excellent, with correlation coefficients of 0.80, 0.93 and 0.51 respectively. The test-retest reliability for the total duration factor and amplitude factor of the DIMS was also good, with coefficients 0.76 and 0.84. Excellent test-retest reliability was obtained for the DIMS-D subscale both for the duration factor, amplitude factor and the summation of both factors. In-depth analysis of the DIMS-D region scores showed moderately high to excellent test-retest reliability for all constructs, which implies that the presence and severity of dystonia during powered mobility can be reliably measured over time, both for the voluntary and overflow movements.