Distribution of motor types in cerebral palsy: how do registry data compare?

The aim of this study was to describe the distribution of types of motor disorder (motor type) in a population-based registry of children with cerebral palsy (CP), to examine any trends in motor type distribution over time, and to make comparisons with other populations.

Individuals born in Victoria, Australia, between 1970 and 2003 with congenital CP were identified from the Victorian Cerebral Palsy Register, 3297 of whom were included in the study (1840 males, 1457 females). Those who had a hypotonic motor type, those whose brain abnormality was believed to have developed after 28 days of life, and those with missing data were excluded from the study. The proportions of each motor type were calculated and plotted by year of birth. Logistic regression analyses were used to assess the mean change in odds per year of birth. A systematic review of the international literature was undertaken and comparison data were extracted based on previously devised criteria. The degree of heterogeneity was assessed and comparisons were made according to geographical region and reporting period.

In Victoria, the predominant motor types for individuals with CP born between 1970 and 2003 were spasticity (91%), ataxia (5%), and dyskinesia (4%). There was no clear trend for any motor type over time. The mean proportions from two other large data sets were similar but there was considerable heterogeneity between 29 individual CP registries, mainly because of differences in the classification of mixed motor types.

A more objective method for determining the predominant motor type is required to make the classification of motor type in CP more consistent and reliable.