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

Developmental dysphasia, a severe childhood learning disorder, is thought to result from problems in hemispheric specialization involving both left and right cerebral hemispheres. Regional cerebral blood flow (rCBF) was measured at rest and during stimulation of both hemispheres independently: dichotic listening for the left, dichaptic palpation for the right. Eight right-handed boys with expressive dysphasia, aged 8 to 12 years, were investigated using SPECT and compared with eight right-handed age-matched boys with Duchenne muscular dystrophy with reading disorders but normal speech. rCBF values at rest were also compared with those of five right-handed age-matched normal boys. In the dichotic task, children with dysphasia differed from children 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 bilaterally for children with dysphasia whereas in children with dystrophia rCBF increased only in the right hemisphere. At rest the physiological asymmetry was reversed in favor of the right hemisphere in all areas except Broca's area. Surprisingly, the same applied at rest and for all areas in children with 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 could also be related to abnormal hemispheric specialization.

[Corpus callosum syndrome in children]. / Le syndrome calleux chez l'enfant.

The survey of callosotomized children is a difficult because they often present a severe epilepsy with mental retardation. The younger the child, the better he recovers. The child can be considered as a physiological split-brain. If one compares commissurotomized children with those presenting an agenesis of the corpus callosum, the later ones have, to a certain extent, an interhemispherical transfer which suggests supportive ipsilateral or sub-cortical connections.

[Cerebral achromatopsia without prosopagnosia, alexia, object agnosia]. / Achromatopsie cérébrale sans prosopagnosie ni alexie ni agnosie des objets.

A 62-year-old woman was admitted for a disorder of color vision. This cerebral achromatopsia was isolated, without prosopagnosia, alexia, object agnosia. MRI showed bilateral temporo-occipital infarcts, including lingual and fusiform gyrus. Neuropsychological examination and topographic hypotheses are discussed.

[Developmental dysphasia]. / Les dysphasies de développement.

Developmental dysphasia is characterized by severe, specific and unexplained developmental language impairment. Phonologic and syntactic disorders of expressive language and perceptual deficit are almost always present. Moreover, certain specific linguistic symptoms are particular to each dysphasic child, explaining the efforts to classify different forms of dysphasia. The most important point is to separate receptive dysphasia from the expressive on the one hand, and severe forms from the mild which are closed to "simple language delay", on the other. The evolution of oral language is variable, but often long and difficult, with persistent linguistic deficit. Reading and writing acquisition is usually difficult, although very important for the socio-professional outcome and language improvement. The etiology remains unknown and is probably multifactorial. One pathogenic hypothesis is based on the absence of the usual hemisphere specialisation related to various prenatal or postnatal events. A genetic basis seems likely for certain dysphasic children. Development of knowledge about this condition and improvement of both speech therapy and teaching are essential for the outcome of these otherwise intelligent and normal children.

Study of unilateral hemisphere performance in children with developmental dysphasia.

Hemisphere specialization for language was studied in 10 children with expressive developmental dysphasia (DD) (mean age 10 years 4 months) submitted to a dichotic listening task (in a word free-recall task and forced-attention task) and a finger tapping/vocalization dual-task paradigm. A nonsense shape dichaptic task was also introduced to control right hemispheric processing. Performances of dysphasic children were compared to those obtained from 15 normal children. The results showed that controls had a right ear advantage in free-recall (words) dichotic listening task and a significant right ear advantage in forced-right-attention task, with a change in ear asymmetry as a consequence of instruction. In the dysphasic group we observed a significant right ear advantage in the free-recall dichotic listening task and no change in ear asymmetry during forced right or forced left condition. Results in time sharing paradigm and nonsense dichaptic task are more difficult to interpret, because there was no interaction between group and condition. These results cannot support a complete left hemisphere dysfunction in developmental dysphasia.

Sleep EEG and developmental dysphasia: lack of a consistent relationship with paroxysmal EEG activity during sleep.

In order to clarify the relationship between developmental dysphasia and EEG abnormalities, paroxysmal activities during sleep were studied in a series of 24 children with expressive developmental dysphasia (mean age 8 years) and compared to a control group of 39 children (mean age 9 years). The children of both groups were selected excluding cases with prior history of neurological disease or epilepsy. In the control group, 37 children had normal sleep EEG while 2 children had paroxysmal abnormalities. In the dysphasic group, epileptic abnormalities were observed in 9 cases, rare in 4 cases and frequent in 5 cases (density: 2.5 to 66.2% of total sleep time). Nevertheless, paroxysmal abnormalities did not reach the frequency described in the Landau-Kleffner syndrome, and it is unlikely that EEG abnormalities could have produced dysphasia.

[Agrypnia (organic insomnia)]. / Les agrypnies.

The word agrypnia, ie, organic insomnia, was first used to describe a patient with a Morvan fibrillary chorea, which is an ill-delineated syndrome. This review considers the experimental insomnia created by raphe nuclei, anterior hypothalamic, or thalamic lesions. There are some papers reporting REM and non-REM sleep reduction in man after vascular, traumatic or degenerative lesion of the pons. There is only one case of agrypnia due to a bilateral stereotatic thalamic injury. Infectious agrypnia (trypanosomiasis, Von Economo) may exist but has not been documented by polygraphic means. Fatal familial insomnia induces a precocious agrypnia and leads to death with vegetative and motor disturbances. It is associated with an abnormal prion-protein which may interfere with gabaergic synapses. Finally agrypnia in humans corresponds to either lesionnal or infra microscopic synaptic prion linked disorders.