Paediatric motor phenotypes in early-onset ataxia, developmental coordination disorder, and central hypotonia.

Only 32 children were studied, with 11 children with early-onset ataxia, 10 with developmental coordination disorder, and 11 with central hypotonia, so small group differences may not hold in larger samples. All children had already been clinically diagnosed before assessment, and six of the children were patients of one of the assessors, so the assessors may not have been fully independent. The assessors judged videotaped motor tasks rather than the full clinical examination, and previous outpatient encounters may have influenced their judgements. One child labelled as central hypotonia was later diagnosed with limb-girdle muscular dystrophy, and one child with developmental coordination disorder was later found to have a KLF7 gene mutation, although the authors said excluding the hypotonia case would not have changed the outcomes. The reassessment with early-onset ataxia features was done only for children whose early-onset ataxia and developmental coordination disorder phenotypes had not separated consistently.

Do not read the 90% recognition of early-onset ataxia as evidence that motor testing alone can diagnose it. Complete agreement with the clinical diagnosis occurred in only eight of 11 children with early-onset ataxia, and five of 21 children with early-onset ataxia or developmental coordination disorder were assigned to the opposite group by an assessor.