Seminar 3 –
Characteristics and Comorbidity

Amanda Kirby:
The Dyscovery Centre,
University of Wales, Newport

Co-morbidity and key characteristics: Implications for research and clinical practice of DCD

DCD plus
Confusion over terminology in both research and clinical settings leads to different terms being used and comparison of work undertaken difficult to achieve. The term comorbidity is a term frequently used to highlight the heterogeneity of DCD. However it is not an accurate term to be used as it in fact means: “The presence of co-existing or additional diseases with reference to an initial diagnosis or with reference to the index condition that is the subject of study. This has been described as two or more “diseases” with separate and different aetiologies which can present simultaneously or sequentially. (Perrin & Last, 1995).Alternative terms that could be used include:

Caron and Rutter’s discussed in 1991 that a failure to attend to co-morbid patterns may lead to misleading conclusions by researchers and negative intervention results from practitioners and is as true today as15 years ago. Much research has tried to study the child with DCD alone, but if this is indeed a rarity it may be more use to look at the different patterns of overlap and see how this alters the presentation
Rates of overlap will be influenced by:

Do different patterns of overlap have different outcomes for the child with DCD?
The aetiology and mutual interdependence of various developmental disorders may affect the presentation, for example the child with ADHD and DCD has greater difficulties in social interaction and other consequences than the DCD child alone. Overlap with ADHD certainly seems to have a worse long term prognosis. Hellgren et al’s (1993) long term study of individuals showed that those with a mixed picture were more likely to continue to have difficulties into adulthood. Rasmussen’s (2000) longitudinal community based study followed children who had been diagnosed at seven years with DCD and found that at 22 years of age the research participants were more likely than their matched controls to be unemployed, to have had problems with breaking the law, to be alcohol or drug misusers and to have mental health difficulties. 80% of the participants with DCD/ADHD had poorer outcomes compared to 13% in the comparison group without DCD and it was the combination of the two that seemed to give a “gloomier prognosis”.

Does gender affect the type of overlap?
Gender may also influence presentation as Sigurdsson et al (2002) showed that DCD + anxiety seems to be different in girls and boys with three times greater maternally reported anxiety in males than females at 11 and 16 years.

Does one symptom increase the likelihood of particular pattern of overlap?
The outcomes for the individual are affected by the variables that are occurring across time and in the context of a changing environment. Particular symptoms such in attention may affect the ability of the child to practice a task and improve performance such as a child who has poor concentration and inattention may have poorer ball skills than peers because it is harder to maintain concentration and practice these skills. However it is difficult to untangle how these two interact. Tseng et al( 2004) showed that “Attention and impulse control were consistently found to be important predictors of both fine and gross motor skills in children with ADHD” .However Kooistra et al (2005) recently showed that reading disorder was the greatest predictor of motor difficulties and that ADHD alone did not produce a difference in motor skill acquisition. Work by Kirby and Salmon (unpublished) have shown that the interaction of ADHD and DCD has a worse social prognosis for the child. Is this a cumulative effect?

Does observing the overlap lead us to a greater understanding of the underlying aetiology of DCD?
Kirby (2005) has shown an overlap/similarity in functional patterns between DCD and Benign Joint Hypermobility Syndrome and this may allow us to understanding some of the mechanisms of dysfunction in this group as they are seen to have greater degrees of freedom. Research in adults with BJHS has also shown associated dysautonomia (Gazit et al, 2003) and may allow us to consider further directions for research in terms of physiological measures to gain greater understanding.

What about variation “within” DCD?
Attempts have been made to subtype children with DCD and to understand the underlying aetiology and the implications for treatment. (Sugden & Chambers, 1998; Sims et al, 1996; Wilson et al, 2002). Kirby has recently looked at a clinical case series of 141 children diagnosed with DCD with scores on the Movement ABC battery (Henderson and Sugden, 1998) < 5%, and meeting DSM1V criteria.
The proportional relationship of one area of the subtest to another was examined to demonstrate the differences between children all with a similar diagnosis of DCD and showed only one third of the children showed difficulties in all three areas of the MABC subtests and wide variability in the other areas.

Further questions to consider
How could there be a more effective working definition of DCD for research and clinical practice in order to gain consistency in usage? Should DCD be a symptom based disorder and not imply aetiology? Do children with DCD have different phenotypes? (An "outward, physical manifestation”). Are the same exclusion criteria being applied, and if not how does this influence what is or is not co-morbid/associated, and the impact this have in trying to compare one study with another.

Should there be a “tighter” or “looser” definition of DCD?
Should DCD be kept or because of the rate of overlap should a broader term be used such as Atypical Brain Disorder? Proponents of a symptom based approach have included: Kaplan et al (1998, p.472) who states “although there is often one feature of these children’s difficulties that stands out from all others it is rarely the case that it is an entirely isolated problem.” She later (2001) suggested that each syndrome represents a semi-random cluster of symptoms. She proposes that by using a single term for all learning difficulties and then focusing on the individual’s symptom patterns, would remove the pressure to pigeonhole children and would result in looking at the overall picture of strengths and weaknesses. Visser (2003, p.484) also discusses the overlap of specific learning difficulties and that they reflect a “generalized deficit, instead of a pure language, attention or a co-ordination problem .This has led to an increased focus on the development of theories that identify the common cause of these symptoms.” However this approach may reduce our understanding of the underlying movement difficulties.

Should we be considering a more dynamic systems disruption model?
Virtually all-human diseases result from the interaction of genetic susceptibility factors and modifiable environmental factors, broadly defined to include infectious, chemical, physical, nutritional, and behavioural factors. Seeking a gene or neural substrate for a multidimensional system may be hard. Models of systems disruption may be more suitable for modelling both causation and functional impairment than attempts to find single genes, toxins, neurotransmitters or neural systems dysfunctions. A systems disruption model may provide a means for the systematic incorporation of multiple endophenotypes into research programs.
There is a need for guidelines in DCD for clinical and research management as practice varies across the UK. This is variation in practice has also been noted in ADHD who concluded that diagnostic practice varies between clinicians as shown by their use of classification systems and terminology. (McKenzie, I. & Wurr, C. (2004)

Potential working definition for DCD for the future?
This was suggested as a tentative way forward to be able to work with overlap and to gain a greater understanding of DCD.

A core motor deficit

Failure of acquisition of motor skills, which is not explicable and unexpected on the basis of impaired general learning experiences compared with peers from similar cultural and social backgrounds and has adequate intelligence.

Criteria

Inclusion
The individual has difficulties in one or more areas: e.g. individual in a stationary environment, individual in a changing environment, individual has difficulty with tool usage.

Starting before the age of 7 years

Presents with difficulty being able to adapt in a new environment or undertaking a new skill compared with peers

Has an impact on the individual in more than 1locations – such as school/work/home/community

Exclusion
A degenerative or acquired brain injury

References

1. Barnett, AL., Kooistra, L., & Henderson, SE. (1998) "Clumsiness" as syndrome and symptom. Human Movement Science; 17:435–47.

2. Caron, C., & Rutter, M. (1991). Comorbidity in child psychopathology: Concepts, issues and research strategies, Journal of Child Psychology and Psychiatry, 32, 1063-1080.)

3. Gazit, Y., Nahir, AM., Grahame, R., & Jacob G. (2003) Dysautonomia in the hypermobility syndrome. American Journal of Medicine; 115:33-40.

4. Hellgren, L., Gillberg, C., Gillberg, C., & Enerskog, I. (1993). Children with deficits in attention, motor control and perception (DAMP) almost grown up: Psychiatric and general health at 16 years. Developmental Medicine and Child Neurology, 35, 881–892.

5. Kaplan, BJ., Wilson, BN., Dewey, D.,& Crawford SG. (1998) DCD may not be a discrete disorder. Human Movement Science 17:471–490.

6. Kaplan, B., Dewey, D., Crawford, S., et al. (2001)The term comorbidity is of questionable value in reference to developmental disorders: data and theory. Journal of Learning Disability; 34:555–65.

7. Kooistra, L., Crawford, S., Dewey, D., Cantell, M., & Kaplan, BJ. (2005) Motor correlates of ADHD: contribution of reading disability and oppositional defiant disorder. Journal of Learning Disability. May-Jun; 38 (3):195-206.

8. McKenzie, I. & Wurr, C. (2004) Diagnosing and treating attentional difficulties: a nationwide survey. Archives of Disease in Childhood, 89, 913-916.

9. Missiuna, C & Polatajko, H. (1995) Developmental dyspraxia by any other name: are they all just clumsy children? American Journal of Occupational Therapy Nov-Dec; 49(10):1084

10. Perrin, S., & Last, C.G. (1995). Dealing with comorbidity. In: A. Eisen, C., Kearney, & C. Schaefer (Eds.), Clinical handbook of anxiety disorders in children and adolescents, New York: Jacob Aronson Press.

11. Peters, JM., Barnett, AL., & Henderson, SE. (2001) Clumsiness, dyspraxia and developmental co-ordination disorder: how do health and educational professionals in the UK define the terms? Child Care Health Development. Sep; 27 (5):399-412

12. Rasmussen, P., &Gillberg, C.(2000) Natural outcome of ADHD with developmental coordination disorder at age 22 years: a controlled, longitudinal, community-based study. American Academy of Child and Adolescent Psychiatry. Nov; 39 (11):1424-31.

13. Sigurdsson, E., van Os, J., & Fombonne E (2002) are impaired childhood motor skills a risk factor for adolescent anxiety? Results from 1958 UK birth Cohort and National Child Development Study. American Journal of Psychiatry June 1044-1046

14. Sims, K, Henderson, S.E., Morton, J., &Hulme C. The remediation of clumsiness, II: is kinaesthesis the answer? Developmental Medicine and Child Neurology. 1966; 38, 988-997

15. Sugden, DA., & Chambers, ME. Intervention approaches and children with developmental coordination disorder. Pediatric Rehabilitation 1998; 2, 139-147.

16. Tseng MH, Henderson A, Chow SM, Yao G (2004).Relationship between motor proficiency, attention, impulse, and activity in children with ADHD. Developmental Medicine and Child Neurology. Jun; 46 (6):381-8.

17. Visser J (2003). Developmental coordination disorder: a review of research on subtypes and comorbidities Human Movement Science. Nov; 22(4-5):479-93

18. Wilson, PH., Thomas, PR., & Maruff, P. (2002)Motor imagery training ameliorates motor clumsiness in children. Journal of Child Neurology; 17, 491-498

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