Hemispheric specialization using SPECT and stimulation tasks in children with dysphasia and dystrophia

Developmental dysphasia, a severe childhood learning disorder, is thought t o result from problems in hemispheric specialization involving both left an d right cerebral hemispheres. Regional cerebral blood how (rCBF) was measur ed at rest and during stimulation of both hemispheres independently: dichot ic listening for the left, dichaptic palpation for the right. Eight right-h anded boys with expressive dysphasia, aged 8 to 12 years, were investigated using SPECT and compared with eight right-handed age-matched boys with Duc henne muscular dystrophy with reading disorders but normal speech. rCBF val ues at rest were also compared with those of five right-handed age-matched normal boys. In the dichotic task, children with dysphasia differed from ch ildren with dystrophia by failure to increase rCBF in the left hemisphere, in Broca's area, but rCBF increased in the right hemisphere, in the region homologous to Broca's area. In the dichaptic task, rCBF increased bilateral ly for children with dysphasia whereas in children with dystrophia rCBF inc reased only in the right hemisphere. At rest the physiological asymmetry wa s reversed in favor of the right hemisphere in all areas except Broca's are a, surprisingly, the same applied at rest and for all areas in children wit h dystrophia. These results confirm that functional specialization of both hemispheres is impaired in developmental dysphasia. Moreover, they suggest that learning disabilities associated with Duchenne muscular dystrophy coul d also be related to abnormal hemispheric specialization.