Shift to righthandedness in Rett syndrome around age 7.

This paper confirms Nomura's finding (Nomura et al, 1984) that almost all of those children with Rett syndrome under 7 who grasp objects are lefthanded. It is suggested that the lefthandedness in Rett syndrome up to age 7 comes from a functional lateralization of the cerebral hemispheres similar to that which Birkmayer and Rett proposed for normal infants up to age 1 (Birkmayer and Rett, 1954). However, examination of children over 7 showed that almost all of those patients who grasp objects prefer the right hand and show symptoms of disturbance of the functions of the pyramidal tract that are more pronounced in the left than in the right upper limb. It is suggested that in connection with the severe developmental retardation of the CNS in Rett syndrome the right shift factor of handedness (Annett, 1981) has a belated manifestation. Within the framework of a regression of the CNS there occurs a regression which is more pronounced in the right cerebral hemisphere than in the left.