Prenatal alcohol and cocaine exposure: Influences on cognition, speech, language, and hearing.

The questions posed at the beginning of this review were to determine if prenatal alcohol- and cocaine-exposure affected speech, language, hearing, and cognitive development, to describe the specific nature of the delays or disorders, and to determine if there were any exacerbating environmental conditions. FAS occurs in infants whose mothers had a history of daily, heavy alcohol use, or intermittent alcohol use, such as binge drinking.

Cognitive impairment, learning disabilities, and behavioral disorders are the central nervous system manifestations of FAS, and cranio-facial abnormalities are also present. Because prenatal alcohol-exposure can cause structural and functional brain abnormalities resulting in mental retardation, delays in language acquisition as well as receptive and expressive language deficits are commonly reported, although there are few studies that have focused specifically on the speech and language characteristics in children with FAS. The cranio-facial abnormalities of FAS, which sometimes include cleft palate, make the child prone to otitis media with effusion and conductive hearing loss. The rate of sensorineural hearing loss in children with FAS is similar to that of groups with other cranio-facial disorders, although an ototoxic effect of PAE has been shown in experimental animals. The family environment in which one or both parents is a heavy alcohol user presents challenges to a child with normal intelligence, but may be especially deleterious to the child with mental retardation.

Some have questioned whether prenatally cocaine-exposed infants exhibit any lasting, significant effects on speech, language, hearing or cognition that can be attributed strictly to the drug itself and its teratogenicity. Early research focused on the physical and cognitive development of PCE infants had shown a significant effect of such exposure, but long-term, prospective studies of children with PCE obtained conflicting results. The longer term (i.e. 4–7 years) outcomes appear to show subtle, but statistically significant effects. Height, but not weight, is related to PCE, especially for children born to mothers over 30 years of age. Subtle cognitive effects are also seen, such as in arithmetic, object assembly, and information. PCE effects on cognition may be masked by the care-giving environment, with children who received the greatest prenatal exposure placed in adoptive or foster homes in which the care-giver has higher educational achievement than the biological parent or relative.

Speech and language effects of PCE have been measured in prospectively studied cohorts. In general, a small “cocaine effect” can be assayed from careful, multi-variate analysis methods. More importantly, when other variables are allowed to interact with PCE, such as concomitant exposure to alcohol, tobacco, and marijuana, lack of prenatal care, and other maternal characteristics, greater effects are seen. PCE does not occur in isolation from other risk factors for speech, language, and cognitive delay, or disability. It is therefore plausible to consider the child with PCE at “cumulative risk” for language delay or disorder.

There is no evidence that PCE by itself is a risk factor for sensorineural hearing impairment. ABRs measured from neonates with PCE show prolonged waves I–V inter-peak latencies, interpreted as an abnormality of central auditory function, specifically, neural transmission time within the brainstem. Binaural interaction components measured at brainstem and cortical levels indicate differences between PCE and NE newborns. These are likely related to the effect of cocaine on synaptic function within the auditory nervous system, similar to that causing the prolonged inter-peak latencies. Both prolonged inter-peak latencies and absent or diminished binaural interaction components have been associated with central auditory-processing disorders when evident in older children.

The strong effect of the home environment for ameliorating the effects of prenatal cocaine-exposure suggests that a family-focused approach for cognitive, language and social-emotional habilitation would be beneficial to all.