Fully two-thirds of children say their first words between 9 and 12 months of age and their first word combinations before their second birthday; when this does not happen, it becomes a matter of parental concern. Children who fail to reach these milestones at the stated times fall into two general categories. In one group there is no clear evidence of cognitive delay or impairment of neurologic or auditory function. In a second group, the speech delay has an overt pathologic basis.
The first group, comprising otherwise normal children who talk late, is the more puzzling. It is virtually impossible to predict whether such a child’s speech will eventually be normal in all respects and just when this will occur. Prelanguage speech continues into the period when words and phrases should normally be used in propositional speech. The combinations of sounds are close to the standard of normal vowel–consonant combinations of the 1to 2-year-old, and they may be strung together as if forming sentences. Yet, as time passes, the child may utter only a few understandable words, even by the third or fourth year. Three of 4 such patients will be boys and often one discovers a family history of delayed speech. When the child finally begins to talk, he may skip the early stages of spoken language and progress rapidly to speak in full sentences and to develop fluent speech and language in weeks or months. During the period of speech delay, the understanding of words and general intelligence develop normally, and communication by gestures may be remarkably facile. In such children, motor speech delay does not presage mental backwardness. (It is said that Albert Einstein did not speak until the age of 4 and lacked fluency at age 9.)
Nevertheless, the eventual acquisition of fluent speech is no guarantee of normalcy (Rutter and Martin). Many such children do have later educational difficulties, mainly because of dyslexia and dysgraphia, a combination that is sometimes inherited as an autosomal dominant trait, again more frequently in boys (see further on). In a smaller subgroup, articulation remains infantile and the content of speech is impoverished semantically and syntactically. Yet others, as they begin to speak, express themselves fluently, but with distortions, omissions, and cluttering of words, but such patients usually acquire normal speech patterns with development.
A second broad group of children with speech delay or slow speech development (no words by 18 months, no phrases by 30 months) comprises those in whom an overt pathologic basis is evident. In clinics where children of the latter type are studied systematically, 35 to 50 percent of cases occur in those with global developmental delay or “cerebral palsy.” Hearing deficit explains many of the other cases, as discussed later, and a few represent what appears to be a specific lack of maturation of the motor speech areas or an acquired lesion in these parts. Only in this small, latter group is it appropriate to refer to the language disorder as aphasia, that is, a derangement or loss of language caused by a cerebral lesion. Aphasia, when it occurs as the result of an acquired lesion (vascular, traumatic) is essentially of the motor variety and typically lasts but a few months in the child. It may be accompanied by a right-sided hemiplegia. An interesting type of acquired aphasia, possibly encephalitic, has been described by Landau and Kleffner in association with seizures and bitemporal focal discharges in the EEG (see “Seizures Presenting in Early Childhood” in Chap. 16).