Mental Retardation

(Down's Syndrome and other Chromosomal Abnormalities; Mental Deficiency)

In general, mental retardation is characterized by subnormal intelligence, defined as an IQ of 70 or lower, that prevents a person from functioning normally in society. The impairment often becomes evident during infancy or early childhood; sometimes the signs first manifest themselves after the child enters school and is unable to keep up with other children.

About 1 percent of the population is classified as retarded, with the degree of impairment ranging from mild to profound. Males are affected one and a half times more often than females. In about 75 percent of all cases, no identifiable biological cause can be found for the retardation. In the remaining 25 percent, the most common causes are chromosomal abnormalities, with Down's syndrome, formerly called mongolism, being the most familiar. Children with this syndrome have Mongoloid features, including slanted eyes, a flat nose, and epicanthal eyelids, the folds that are normal among Asians. It has been determined that the abnormalities are caused by an extra chromosome 21.

About one in 700 babies born in the United States has Down's syndrome; however, the incidence rises to one in 100 when the mother is over the age of 32. The frequency continues to increase with advancing age.

Genetic metabolic disorders, such as phenylketonuria (PKU), in which the baby inherits a gene that precludes normal metabolism. Often, such a child lacks one essential enzyme; PKU babies, for example, are missing a liver enzyme necessary to metabolize phenylalanine, an essential amino acid.

Alcohol use during pregnancy, can result in fetal alcohol syndrome (FAS), in addition to mental retardation, FAS children may have severe heart defects, deficient growth, slow motor development, and a variety of facial and skeletal malformations.

Malnutrition that results in a premature or low birth-weight baby. This problem is most common among teenagers from economically deprived families.

Thyroid deficiency, which can cause cretinism, profound retardation, and growth problems if it is not detected and corrected shortly after birth.

Infections, such as rubella, AIDS, toxoplasmosis, syphilis, systemic herpes, meningitis, encephalitis, and other diseases, that have been contracted before birth or during early childhood.

Lead poisoning and exposure to other toxic substances, either before birth or during childhood.

Head trauma, most often from falls and other accidents, as well as child abuse. Brain damage also may occur from lack of oxygen during birth, near drowning, or other mishaps.

Diagnostic Studies and Procedures

Down's syndrome, severe brain deformity, and certain other defects can be detected before birth by amniocentesis, ultrasound, and other prenatal examinations. Doctors generally recommend these tests for women over age 35 or those of any age with a family history of certain genetic disorders.

Some forms of retardation are apparent immediately after birth, but others may not show up until the child's development begins to lag.

During an examination, a doctor will look first for such characteristic physical features as a head that is too large or too small. In addition, she will order routine blood and urine tests, and perhaps chromosome analyses, enzyme analyses, and hormone studies. X-rays or a CT scan may also be needed to see if there are abnormalities such as excessive fluid in the brain. A complete neurologic examination will be done, which may include an electroencephalogram, the measuring of electric impulses in the brain cells.

Hearing should definitely be tested: some children assumed to be mentally retarded turn out to have a hearing problem and normal intelligence. As the child grows, intelligence will be assessed, although the results of early IQ tests do not necessarily predict the achievable level of later functioning.

Medical Treatments

Some forms of retardation can be prevented by early medical intervention. For example, if the abnormalities of PKU and low thyroid hormone levels are detected at birth, they can be corrected by early dietary treatment and hormone replacement. In some cases, excessive brain fluid (Hydrocephalus) can also be corrected, minimizing the extent of brain damage.

The physical defects that often accompany mental retardation can be similarly treated. For example, cleft palate, heart abnormalities, and the deformities common in fetal alcohol syndrome may be repaired surgically.

Later, drug therapy may be prescribed to treat hyperactivity, anxiety, depression, and other problems related to mental deficiency. Otherwise, treatment generally centers on helping the child achieve his fullest potential. In the past, retarded children were often warehoused in institutions because it was generally assumed that they could never achieve self-sufficiency. We now know that up to 85 percent of the mentally retarded are capable of developing social and vocational skills that will allow them to become at least partially self-supporting. And the more supportive and enriched their environment, the better their outlook will be.

Many learn to read up to a sixth grade level. Behavior is often a problem, but with proper guidance and understanding, they can also achieve necessary social skills.

People who work with the mentally handicapped generally agree that, even though these children require special education and will never catch up with their normal peers, they do best if they are taught in a regular school setting where they can imitate and learn from other children. Of course, the child is not the only one who needs help; parents and other family members also benefit from support and psychological counseling (see Self-Treatment).

Alternative Therapies

Increasingly, psychologists, teachers, and parents are employing alternative therapies to help retarded children overcome physical and social handicaps. Some of the more useful include:

Art, Dance, and Music Therapy. These modalities, when instituted at an early age, give the child additional means of expression and also help to improve motor skills and behavior. These and other forms of creative or play therapy are not only enjoyable, but can also help the child to express feelings of frustration and anger.

Nutrition Therapy. Some metabolic disorders require a special diet, which should be devised by a clinical dietitian experienced in treating such problems. Parents should resist the temptation to give high-dose vitamins and other nutrition remedies without checking with a doctor or a registered dietitian. Excessive amounts of some nutrients can exacerbate a metabolic condition.

Some types of mental retardation result in compulsive eating habits. In such cases, food intake must be controlled to prevent severe obesity. Some parents are forced to keep refrigerators and food cabinets locked.

Physical Therapy and Exercise Conditioning. Mental retardation is often accompanied by poor muscle tone, lack of coordination, and slow development of motor skills. The parents of such an infant are often instructed to exercise the child's limbs passively and to encourage as much movement as possible A physical therapist can teach parents the best way to exercise a child at different ages to improve muscle tone, strength, and coordination. In some cases, braces or other devices may be needed to help the child learn to walk.

Pet Therapy. Numerous special education programs employ animals to help improve motor development and social skills, and build self-esteem by introducing the child to a loving and accepting living creature. Animals used in pet therapy with the retarded range from dolphins and horses to cats and goldfish. A pet for a retarded child should be gentle and yet tolerant of rough handling -- a large dog that likes children is a better choice than a small, nervous lap dog or a cranky cat.

Self-Treatment

Parents of a retarded child often harbor feelings of anger and guilt; others are simply overwhelmed by the extra responsibilities, especially if they have other children. Counseling, family therapy, and support groups can help all family members deal with their own feelings and also gain insight into how to help the handicapped child.

Teaching good behavior can be one of the most trying aspects of bringing up a retarded child. Of course, even highly intelligent children can develop behavior problems, but learning social skills is especially difficult for the mentally retarded, because usually they cannot tolerate frustration and are unable to control their impulses. Experts agree that positive reinforcement works best. Reward good behavior, while ignoring or gently correcting the bad.

If a child is engaging in dangerous or destructive activities, you can resort to the same tune-out technique that works for normal children. Remember, however, that it takes longer for a retarded child to learn (or unlearn) behavior, so don't expect that one or two time-outs will do the trick.

Other Causes of Mental Deficiency

Mental retardation is sometimes a component of autism. Parental neglect, failure to thrive, extreme malnutrition, a prolonged high fever or other serious illness, and/or sensory deprivation can lead to diminished intelligence in children who were normal at birth.