Hand preference, extent of laterality, and functional hand use in Rett syndrome.

Residual hand use in functional tasks, extent of laterality, and right or left preference were studied in 145 2- to 24-year-old, postregression Australian subjects with Rett syndrome via parent questionnaire. Hand use was markedly restricted, more for complex than simple and for external (touching food and objects) than internal tasks (scratching, rubbing eyes), suggesting a deficit in cerebral control of external, goal-oriented hand use, which is perhaps genetically determined because there is significantly greater restriction of external tasks in subjects with demonstrated MECP2 mutations. Overall, 33.6% of patients were reported with a left-hand preference, 40.7% with a right-hand preference, and 25.7% with an equal hand preference. Extent of laterality was greater for external than internal and for complex than simple external tasks. Older subjects showed less functional hand use and possibly more overall laterality. However, their hand preference was similar to younger subjects. The anomalous pattern of hand preference in Rett syndrome may be linked to the primary apraxic deficit in this disorder rather than to late manifestation of laterality.