The action of exogenous toxins during pregnancy is another factor to be considered. Severe maternal alcoholism has been linked to a dysmorphic syndrome and developmental delay, but the findings of several studies have not been consistent (see Chap. 41); a similar problem attaches maternal exposure to anticonvulsant medications (see Chap. 15). Surprisingly, maternal addiction to opiates, while causing an opiate withdrawal in infants for weeks or even months (Wilson et al), seems not to result in permanent injury to the nervous system. The importance of exposure to extremely small amounts of environmental lead is also controversial.
The effect of psychologic deprivation on cognitive development has been of interest. Following the observations that complete isolation of young female monkeys had a devastating effect on their later sexual and nurturing behavior, the idea became popular that such deprivation might cause faulty mental development in humans. Orphaned and neglected babies were found to be inactive and apathetic in comparison with those who were constantly stimulated by caring mothers. But surprisingly, when nurtured properly at a later time, these babies soon caught up with their peers. This general idea of psychologic deprivation has been the basis of many interesting educational programs for neglected children. To this day, however, it has not been proven that sensory, emotional, and psychologic deprivations of a degree observed in humans are the causes of severe developmental delay or repeated scholastic failure. The controversies regarding the effects of prematurity, maternal hypertension, and eclampsia, which are often associated with neonatal cerebral pathology and slowed psychomotor development, have been mentioned earlier in this chapter. The problem is complex and the arguments pro and con have been elaborated by Haywood and Wachs.
A Clinical Approach to Developmental Delay
As a particular guide to the pediatrician and neurologist who assume responsibility for the diagnosis and management of children harboring a wide array of diseases and maldevelopments of the nervous system, the following clinical approach is suggested. First, as already described, there is an advantage in setting aside as one large group those who are only mildly developmentally delayed from those who have been severely delayed in psychomotor development since early life. With regard to the former group, having no obvious neurologic signs or physical stigmata, one should nevertheless initiate a search for the common metabolic, chromosomal, and infective diseases. In this large group, one must be sure that their deficit is a general one and not one of hearing, poor sight, or the special isolated language and attention deficits.
For patients with moderately severe and very severe cognitive deficits, one begins with a careful physical examination, searching specifically for somatic stigmata and neurologic signs, as summarized by Vasudevan and Suri. Abnormalities of eyes, nose, lips, ears, fingers, and toes are particularly important, as are head circumference and a variety of neurologic abnormalities, as outlined in
Table 37-8. Data so obtained allow classification into one of three categories, as follows:
In those with somatic abnormalities (with or without obvious neurologic signs), one assumes the presence of a maldevelopment of the brain, possibly caused by a chromosomal abnormality. The psychomotor retardation is usually severe and often nongenetic and, as a rule, has a well-defined neuropathology. Diagnosis is determined by the gestalt of physical signs. The possible maldevelopments are numerous and diverse and are summarized in Tables 37-1 and 37-8; some of the main ones are described earlier in the chapter. Inevitably, one turns to the several atlases to denominate the syndromes (Holmes et al; Jones).