Even though causative links may not have been established, there is good reason to want to have an idea of how many known or suspected risk factors are present in any child. If you are seeing a child early in the educational process, this information could help you determine how likely a future problem might be. Details about potential risks also help in formulating conclusions about the prognosis for recovery or improvement following treatment or therapy. Awareness of the potential impact of risk factors can lead to prevention of problems for future patients.
It is helpful to note the type, severity,
and number of past occurrences that are potentially contributory to visual
and learning difficulties. Although they might not be known to be causative,
many past events are at least coincidental with learning difficulties.
This is the concept of risk - that a child has a better than average chance
of having a condition (e.g., reading disability) based on some historical
event or medical condition. It is best thought of in epidemiological terms
such as odds ratio or relative risk. If a child has a positive history
of an exposure, then he or she is statistically more likely to have an
unfavorable outcome. For example, if the odds ratio of a child having severe
learning disabilities when the mother was on antidiabetic medications was
1.99, that would mean the child was twice as likely to have the disability
as a child of a nondiabetic mother (all else being equal). In addition
to the importance of singular events, there is evidence that the cumulative
and interactive effects of multiple exposures may be even more significant.
A listing of some conditions reported to be risk factors for physical, physiological, or behavioral disorders that might eventually result in visual and learning and reading problems. Most of these factors have not been studied in sufficient depth to determine whether they cause learning delays. Some have been investigated only for their effects in the immediate postnatal period, or during infancy. Many have concentrated only on physical changes and have not looked at behavioral or learning outcomes at all.
Make the point that there really is a significant gender issue - males are selectively afflicted with most neurological, psychological and developmental disorders of childhood. The sex ratio is used to express the occurrence of conditions relative to gender and is calculated by dividing the number of males by the number of females and multiplying by 100. The sex ratios of important neurodevelopmental disorders range from 120 for seizure disorders and 130 for severe mental retardation to 219 for learning difficulties, 300 for hyperkinesis, 400 for stuttering and 430 for dyslexia.
The sex differences in neurodevelopmental disorders of childhood follow four distinct trends - males are more commonly affected; when females are affected, the manifestation is more severe; in females, genotype is the likely cause of the condition and thus the manifestations are more specific; in males, manifestations are more diverse owing to a stronger interaction between genotype and environmental factors (including many of the risks we're discussing).
Low birth weight and learning problems are related.
During pregnancy, mother needs increased:
water soluble vitamins
fat soluble vitamins
Chronic hypertension in the pregnant woman can exert a hazardous influence on the fetus by interfering with the blood supply and consequently with the oxygen and nutrient supply by preventing normal placental development or function.
When maternal famine occurs, i.e., when she gets decreased nutrition, it creates a significant reduction in the birth weight of the infant only if it happens during the last trimester.
Using a multivariate list of agents that are risks of growth failure, maternal weight and weight gain are 3X as significant as other factors. Maternal insufficiency is an important risk factor.
Identification and management of high-risk pregnancies is important!
causes are multiple and subtle
studies show prolonged slow head growth in utero affects a child's later development and abilities, particularly perceptual performance and motor ability.
One area where treatment is available =
Inborn errors of metabolism
Inborn errors of metabolism more often than not impair development and behavior. Examples include PKU,
galactosemia, maple syrup urine disease, and urea cycle enzyme deficiencies.
Prenatal management (two types):
1. nutrient is administered - positive intervention
2. nutrient is withheld - negative intervention
Diabetes is another important issue. Pregnancy in an insulin dependent diabetic who is not well controlled may result in a macrosomic infant with multiple congenital anomalies. The risk of fatality and of CNS anomalies can be as much as 28X higher in infants born of diabetic mothers. The risk increases with the length of time the mother has had diabetes. If metabolic control is to be effective, the diabetic woman must control her disease meticulously from before conception until delivery, with particular emphasis on the first 2 months.
Pregnancy - period of -
this gives an increased frequency of contact between pregnant women and physicians; the probability of prescribing drugs increases.
An overwhelming number of drugs (both OTC and Rx) have not been tested for their teratogenic effects on a fetus.
Also now having to deal more and more with the problems of mothers who were on illicit drugs such as cocaine during pregnancy and the learning problems their children experience.
Heroin use may be associated with:
increased rate of prematurity
increased number of SGA infants
as infants the children are irritable and hyperactive, and in early childhood they are distractible and inattentive.
Cocaine use may be associated with:
intrauterine growth retardation
decreased head circumference
One additional example –
emphasizes the point that our society doesn't know all of the potential neurotoxic effects of drugs
Isotretinoin, marketed as Accutane for severe cystic acne, has also been used widely for the treatment of regular acne. Despite a category X FDA rating, it has been used by childbearing women, resulting in children born with MR and/or developing LD.
Mainly preventable, obstetrical trauma.
Very difficult to derive good statistics due to many covariants and confounding factors.
Breech presentation = increased problems
5% died first week; increased morbidity
Breech presentation children also have about a 5X prevalence of hyperkinesis and LD compared to vertex presentations.
Prolonged labor shows up more commonly in the histories of kids with learning problems.
Intracranial vascular injury and hemorrhage can result in significant consequences including motor abnormalities (like CP), seizures, LD, and MR.
Long term meaning of short term changes
Address three questions:
1) do the effects of medication last past the peri-natal period?
2) can the effects be identified in cognitive tasks or attention?
3) can the cognitive effects be identified as LD or visual-perceptual disorders?
Most behavioral studies of the effects of drugs used in childbirth are concentrated in the newborn period. very few address children over 1 year and few of those address subtle visual, perceptual, cognitive or behavioral developmental areas.
Drug effects on neonates
with few exceptions, drugs used in obstetric anesthesia and analgesia rapidly cross the placenta.
Inducers: can give contractions too strong and sustained for safety of the mother and child
Study of about 2000 infants: inhalation
anesthetics & oxytocin related to psychomotor deficits (1st year)
LD: higher incidence of pregnancy and birth complications
higher frequency of induction
meds used in general, particularly inhalation anesthesia
While prenatal and perinatal complications are found more frequently in the histories of children with LD, they provide neither a necessary nor a sufficient explanation.
Fact remains, drug-related deficits in
neonatal responsiveness suggest the possibility of deficits in responsiveness
or learning at later ages. Concern stems from a lack of knowledge about
the effects of a given agent on the fetus or newborn even though the effects
may be known on an adult. The immaturity of the CNS increases its vulnerability
LOW BIRTH WEIGHT
Studied frequently -
prototypic risk group
increasing numbers of survivors
about 7% of surviving infants
at risk for a variety of intellectual tasks
Definition: 2500 G or less (5 1/2 lb.)
< 1500 Very Low Birth Weight (VLBW)
< 1000 Extremely Low Birth Weiht (ELBW)
VLBW can result in mothers with treatable conditions. The risk of VLBW deliveries in black women is significantly increased if they have essential hypertension or a urinary tract infection. The risk is higher in white women who have essential hypertension, a urinary tract infection, pregnancy-induced hypertension, or diabetes. Also higher in any woman who receives inadequate prenatal care.
Mean IQ is lower than average, but still
within normal range
Higher incidence of learning problems
Failure in school/special class placement; found in 30% of LBW children with IQ over 100
found in 36% of LBW children with IQ over 90
LBW infants score: lower on motor development in infancy and preschool years
lower on motor development than same kids mental scores
Visual-motor integration (eye-hand coordination) is an area that has been a very consistent problem for the LBW child !!
Consideration: overwhelming role played
by social factors!
Social factors, i.e., the environment - most reliable predictors of later outcomes
Summary of what we know about
1] decreased intellectual functioning is associated with LBW, may be associated with social factors
2] social factors are more important
3] school performance is not as good for LBW - with social implications
4] visual-motor integration decreased
A growing number of infections are now recognized as important causes of fetal damage when the disease affects the mother during pregnancy - some of these infections can damage the developing nervous system of the child, resulting in a variety of clinical findings such as MR, LD, seizures, CP, microcephaly, and hydrocephaly. The damage appears to be due to direct effects of the infectious agents on the brain tissue. In most cases there is also damage to other organs, particularly included would be the visual system, e.g., neural tube ® colobomas.
Cytomegalovirus = most frequent
cause of congenital infection in US // hematogenous spread from the mother
can be fatal with large organ difficulties.
usually combined MR and high tone deafness.
Rubella = usually epidemics every
6-7 years. Fortunately, in US, with widespread use of vaccine - no epidemic
In 1983, for example, 934 cases, which resulted in 4 cases of CRS.
significant mortality rate. significant damage to CNS.
cardiac damage. ocular effects - cataracts, microphthalmia, glaucoma, chorioretinitis.
can't be vaccinated during pregnancy - vaccine is made from live virus.
language problems. frequently some degree of deafness. also over half have visual perceptual and motor planning problems.
Herpes = Genital (Type 2) HSV
is #2 cause of STD in U.S.
90-95% of newborn infections are due to Type 2 virus,
60% die/50%+ of the survivors have significant neurological sequelae.
Born normally, get heavy dose of HS passing through the birth canal. Identify high risk mothers; herpes status
at the time of delivery - is she still shedding the virus?
Varicella = Varicella (chickenpox)
and Herpes Zoster (shingles) are caused by the same virus.
15% of women of child bearing age are susceptible.
infection in the first 16 weeks => cataracts, MR.,
encephalopathy, microcephaly, club feet, badly scarred extremities
last four days - lesions then or the day after - 10-30% of kids die of disseminated infection (placental transfer)
because he/she gets infected but doesn't stick around long enough to get the antibodies (born too soon).
Syphilis = Spirochete crosses
the placenta and grows in the tissue of the child. Results in MR., paresis
if CNS is affected
can occur at any time during the pregnancy.
Other signs - rash, chorioretinitis, iritis, Hutchinson’s teeth, deafness
Toxoplasmosis = Parasitic; can
be congenital or acquired; wide range of symptoms -
from severe generalized infection with fatality to asymptomatic forms.
Findings = chorioretinitis, anemia, seizures, decreased IQ with microcephaly
In summary, some maternal infections
affect CNS and give brain damage. LD, visual perceptual problems, ocular
disease, etc. are among the defects produced by these infections. The affected
children, unfortunately, are often multiply handicapped.
Of the many industrial chemicals to find their way into the environment, a substantial number are demonstrated neurotoxins at high doses. It is reasonable to ask which of these agents can pass through the maternal placenta and reach the developing gamete, embryo, or fetus, and what the effects might be. Altered behavior or performance on the part of the developing child is one possible result or neurotoxicity at lesser doses.
If the effects are immediate and dramatic
- discovery is easy
If less dramatic - effects are evasive
Lead - oldest and best studied neurotoxin
gives decreased IQ.
younger kids are more susceptible to
lead based paints - chips on floor and off toys
lead does cross placenta
Lead story may be paralleled by other
several candidates: cadmium
estrogen-like substances - pesticides/organic solvents
ALCOHOL AND SMOKING
The old assumption that the placenta protected the embryo from toxic substances has been dispelled, for it is clear that the placenta could be viewed better as a sieve than a wall. Most common drugs - including both alcohol and nicotine - readily cross and circulation levels in the fetal blood are often similar to those in maternal blood.
Animal research has established a causal link between parental exposure to alcohol or nicotine and offspring effects, such as delayed development, hyperactivity, and learning decrements. Human studies, however, are clouded with methodological problems.
Is there a relationship between alcohol and/or nicotine exposure in utero and subsequent LD in offspring after consideration of other related variables?
What do we know?
It is known that smoking is related to
SGA ( about 200 G lighter)
20-40% of incidence of LBW can be explained by smoking and the decrease in BW is directly related to
the number of cigarettes smoked
also, the rates of spontaneous abortion and perinatal mortality are 2X higher
associated with retarded reading at age 7 & 11
if only fathers smoke, problem is about ½ size
Fetal alcohol syndrome [or also called
fetal alcohol effect]
growth deficiency, dysmorphic facial characteristics (small palpebral fissures, flat bridges), CNS dysfunction
and often a major malfunction such as a heart defect
height, weight, and head circumference decreased at first but catch up by 18 months and stay even at ages 4, 7, 14
memory and attention problems observed frequently
Risk: 1/3 of chronic alcoholic mothers
FAS clinical observations:
Hyperactivity (#1); distractible; decreased gross motor; poor fine motor; learning problems; uninhibited; socially engaging
Cognitive, behavioral, communicative, and socialization difficulties may well persist throughout adulthood
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