Motor problems in children with ADHD and clinical effects of Methylphenidate as assessed with the MFNU

Abstract

The Motor Function Neurological Assessment (MFNU) has been developed over a 25 year period based on clinical observations and assessments of children referred for evaluation of possible Attention Deficit Hyperactivity Disorder (ADHD)/Hyperkinetic disorder (HKD). The sub-tests of the MFNU were constructed to demonstrate these motor problems to parents and teachers of these children, and to make changes in motor performance observable when the child was medicated with Methylphenidate (MPH, Ritalin©). The reliability and usefulness of this instrument as a clinical assessment tool has been demonstrated through many years of clinical practice with hundreds of children at the Birkelid Resource Centre prior to the start of the research. However, the MFNU was not originally constructed as a research tool. Since the usefulness of the instrument in this respect is of crucial importance to the validity of our research findings, much effort was put into development of a user manual and DVD with precise instructions for test administration on each subtest, together with rules of interpretation and scoring. The aim of the research projects was to investigate possible relationships between ADHD symptoms and certain motor problems observed in children with this diagnosis. The first research question of our studies, using the MFNU as our research tool, was to establish to what extent the MFNU discriminates between children with and without ADHD. In the first study 25 drugnaïve boys, aged 8-12 years and recently diagnosed as HKD F90.0, and 27 controls without ADHD participated. Highly significant differences between the groups were found on all the MFNU sub-tests. A high percentage of ‘severe problems’ was found in the ADHD group. The control group typically presented few, if any severe problems. When the ‘moderate problems’ and ‘severe’ scores were combined, the ADHD group presented problems within a range of 80 to 96%. The second research question was to investigate the effect of MPH on motor problems in children with ADHD. Twenty-five drug-naïve boys, aged 8-12 years and recently diagnosed as HKD F90.0 participated. A double-blind, placebo controlled, cross-over design was applied, using MPH or placebo capsules. The children were assessed individually with the MFNU twice a day on two different days, with at least one day Summary - 12 - interval. The first trial each day was baseline and the second was the experimental condition. Significant improvements were found on all sub-tests when comparing Baseline to the MPH trial. A Cohen’s d of 1.27 was found, applying ‘Total score’ from the MPH and the Baseline trials. The most pronounced improvements with MPH compared to Baseline were observed on sub-tests assessing high muscular tone. The third research question was to investigate to what extent motor problems are present in positive responders to MPH on their core behavioural problems of ADHD, compared to non-responders. The study group consisted of 73 children. They were retrospectively divided into two sub-groups based on their response to MPH on their core ADHD problems: ‘Medicine responders’ and ‘Non medicine responders’. Highly significant differences were found between the groups on MFNU sub-tests and the ‘Total Score’. The responder group obtained a significantly higher median score than the nonresponder group on all sub-tests. No significant gender or age differences were found in the responder group, nor in the nonresponder group, on any of the MFNU sub-tests. A case study describes changes in motor function on MPH medication in children who did not fully satisfy the ADHD criteria, but were positive medicine responders. The two children were diagnosed with 47, XYY syndrome. The MFNU served as an important supplement in the evaluation of MPH treatment in these children. This shows that the MFNU is valuable in assessment of other syndromes than ADHD. We have shown that the MFNU is a sensitive instrument in the assessment of motor inhibition and high muscle tone in trunk, shoulders, hips and legs in boys with ADHD-C/HKD. The results from the research presented in this thesis support our clinical observations regarding specific motor problems in children with ADHD. We found such problems both in the diagnostic group in general and in children with ADHD, who respond positively to central stimulant medicine, in particular. A single dose of MPH in boys diagnosed as ADHD-C yielded a significant improvement of the motor problems. There was a corresponding weaning effect after the metabolisation of the MPH which is very similar to what is seen in the behavioural symptoms of the syndrome. The results support our suggestion that there may be a close relationship between the motor problems measured by the MFNU and the neurofunctional causes of ADHD.

The MFNU is still in need of further validation research, particularly regarding the use in diagnostic assessment.