Developmental dysphasia: clinical importance and underlying neurological causes.

This survey deals with two aspects of developmental dysphasia which are relevant to child psychiatry; the early diagnosis and treatment of children with developmental dysphasia, which may prevent the progression of learning and behaviour disorders, and the underlying biological causes of this neuro-developmental disorder. The pathophysiology of developmental dysphasia is complex and age-related. In the pre-verbal and early verbal stage, the severity of the clinical picture is primarily determined by concomitant motor pathology (motor dysfunction, dysarthria, general and oral dyspraxia) and by receptive pathology (hearing and auditory perception). In the verbal period, linguistic problems start to play a role, and often combine with oral motor symptoms to present a mixed picture. The various language syndromes do not become clear until some time later. After the kindergarten period, the oral motor and perceptual problems decrease and the language disorders continue to play a role and influence the child's conversation, internal speech and learning a school. In a relatively small number of children without oral motor, perceptual or memory problems, there can be a basic syndrome of "pure dysphasia" without any other neurological signs. These children are very likely to have a genetically determined developmental disorder on a limited neuronal level (no cerebral damage of any kind!) such as an abnormal asymmetry of the hemispheres. In somewhat more than half the patients, this basic syndrome is accompanied by other neurological signs, most of which are indicative of functional disorders of the left hemisphere. There can also be symptoms of the right hemisphere, of the corpus callosum and of the afferent pathway systems for auditory perception. The nature and causes of these anomalies can be multifarious, so that it is unfeasible to speak of THE substrate or THE pathogenesis. Treatment should not be confined to speech therapy techniques, but should also take into consideration the existence of abnormal motor and affective development and can thus only be optimally given by a highly trained team whose expertise also extends to the schooling aspect.