Mental Retardation

Mental Retardation

 Mental retardation is not a disease; rather it is the result of a pathological process in the brain characterized by limitations intellectual and adaptive function.
 The cause of mental retardation often unidentified, and the consequences become evident by a person’s difficulty with intellectual functioning and living skills.
 In the 1800s the notion that mental retardation was based primarily on a deficit in social or moral reasoning was promoted. Since then, the addition of intellectual deficit was added to the concept of inadequate social function.

CLASSIFICATION
 According to the DSM-IV-TR, mental retardation is defined as significantly subaverage general intellectual functioning resulting in, or associated with, concurrent impairment in adaptive behavior and manifested during the developmental period,before the age of 18.
 The diagnosis is made regardless of whether the person has a coexisting physical disorder or other mental disorder.
 General intellectual functioning is determined by the use of standardized tests of, intelligence, and the term significantly subaverage is defined as an IQ of approximately 70 or below or two standard deviations below the mean for the particular test.
 Adaptive functioning can be measured by using a standardized scale, such as the Vinelarid Adaptive Behavior Scale.
 This scale scores communications, daily living skills, socialization, and motor skills (up to 4 years, II months) and generates an adaptive behavior composite that is correlated with the expected skills at a given age
 Approximately 85 percent of persons who are mentally retarded fall within the mild mental retardation category (IQ between 50 and 70).
 The adaptive functions of mildly retarded persons are effective in several areas, such as communications, self-care, social skills, work, leisure, and safety.
 Mental retardation is influenced by genetic, environmental, and psychosocial factors, and in the past years, the development of mild retardation was often attributed to severe psychosocial deprivation.
 More recently, however, researchers have increasingly recognized the likely contribution of a host of subtle biological factors including chromosomal abnormalities. subclinical lead intoxication, and prenatal exposure to drugs, alcohol, and other toxins.
 Furthermore, evidence is increasing that subgroups of persons who are mentally retarded, such as those with fragile X syndrome. Down syndrome, and Prader-Willi syndrome, have characteristic patterns of social, linguistic, and cognitive development and typical behavioral manifestations.

DEGREES OF SEVERITY OF MENTAL RETARDATION
 The degrees, or levels, of mental retardation are expressed in various terms. DSM-IV-TR presents four levels of mental retardation: mild, moderate, severe, and profound.
 The category borderline mental retardation (between one and two deviations below the test mean) was eliminated in 1973.
 Borderline intellectual functioning, according to DSM-IV-TR, is not within the diagnostic boundary of mental retardation and refers to a full-scale IQ in the 71 to 84 range that is a focus of psychiatric attention.
 Mild mental retardation (IQ range, 50—55 to 70)represents approximately 85 percent of persons with mental retardation.
 In general, children with mild mental retardation are not identified until after first or second grade, when academic demands increase.
 By late adolescence they often acquire academic skills at approximately a sixth grade level.
 Specific causes for the mental retardation are often unidentified in this group.
 Many adults with mild mental retardation can live independently with appropriate support and raise their own families.
 Moderate mental retardation (IQ range, 35-40 to 50-55) represents about 10 percent of persons with mental retardation.
 Most children with moderate mental retardation acquire language and can communicate adequately during early childhood.
 They are challenged academically and often are not able to achieve academically above a second to third grade level.
 During adolescence , socialization difficulties often set these persons apart, and a great deal of social and vocational support is beneficial.
 As adults, persons with moderate mental retardation may be able to perform semiskilled work under appropriate supervision.
 Severe mental retardation (IQ range, 20-25 to 35-40) comprises about 4 percent of individuals with mental retardation.
 They may be able to develop communication skills in childhood and often can learn to count as well as recognize words that are critical to functioning.
 In this group, the cause for the milder forms of mental retardation.
 In adulthood, persons with severe mental retardation may adapt well to supervised living situations such as group homes and may be able to perform work-related task under supervision.
 Profound mental retardation (IQ range below 20-25) constitutes approximately 1 to 2 percent of persons with mental retardation.
 Most individuals with profound mental retardation have identifiable causes for their condition.
 Children with profound mental retardation may be taught some self-care skills and learn to communicate their needs given the appropriate training.

Epidemiology
 The prevalence of mental retardation at any one time is estimated to be aout 1 percent of the population.
 The incidence of mental retardation is difficult to calculate because mental retardation sometimes goes unrecognized until middle childhood, when it is mild.
 In some cases, even when intellectual function is limited, good adaptive skills are not challenged until late childhood or early adolescence, and the diagnosis is not made until the time.
 The highest incidences are in school-age children, with the peak at ages 10 to 14.
 Mental retardation is about 1.5 times more common among men than among women.
 In older persons, prevalence is lower; those with severe or profound mental retardation have high mortality rates due to the complication of associated physical disorders.

COMORBIDITY

Prevalence
 Epidemiology surveys indicate that up to two thirds of children and adults with mental retardation have comorbid mental disorders; this rate is several times higher than that in non-mentally retarded community samples.
 The prevalence of psychopathology seems to be correlated with the severity of mental retardation; the more severe the mental retardation, the higher the risk for other mental disorders.
 A recent epidemiological study found that 40.7 percent of intellectually disabled children between 4 to 18 years of age met criteria for at least one psychiatric disorder. .
 The severity of retardation affected the type of psychiatric disorder.
 Disruptive and conduct-disorder behaviors occurred more commonly in the mildly retarded group; the more severely retarded group exhibited psychiatric problems more often associated with autistic disorder such as self-stimulation and self-mutilation.
 The mental disorder that occur among persons who are mentally retarded appear to run the gamut of those seen in mentally retarded persons, including mood disorders, schizophrenia, attention-deficit/hyperactivity disorder, and conduct disorder.
 Those with severe mental retardation have a particularly high rate of autistic disorder and pervasive developmental disorders.
 About 2 to 3 percent of mentally retarded persons meet the criteria for schizophrenia; this percentage is several times higher than the rate for the general population.
 Highly prevalent psychiatric symptoms that can occur in mentally retarded persons outside the context of a mental disorder include hyperactivity and short attention span, self-injurious behaviors (e.g. head banging and self-biting), and repetitive stereotype behaviors (hand flapping and toe walking).
 Personality styles and traits in mentally retarded persons are not unique to them, but negative self-image, low-esteem, poor frustration tolerance, interpersonal dependence, and a rigid problem-solving style are overrepresented.
 Specific casual syndromes seen in mental retardation may also predispose affected persons to various types of psychopathologies.

Neurological Disorders
 Comorbid psychiatric disorders are increased in individuals with mental retardation who also have known neurological conditions, such as seizure disorders.
 Rates of psychopathology increase with the severity of mental retardation; thus neurological impairment increases as intellectual impairment increases.
 The combination of mental retardation, active epilepsy, and autism or an autistic like condition occurs at a rate of 0.07 percent in the general population.

Genetic Syndromes
 Some evidence indicates that genetically based syndromes such as fragile X syndrome, Prader-Willi syndrome, and Down syndrome are associated with comorbid specific behavioral manifestation.
 Persons with fragile X syndrome have extremely high rates (up to three fourths of those studied) of attention-deficit/hyperactivity disorders.
 High rates of aberrant interpersonal behavior and language function often meet the criteria for autistic disorder and avoidant personality disorder.
 Prader-Willi syndrome is almost always associated with compulsive eating disturbances, hyperphagia, and obesity.
 Children with the syndrome have been described as oppositional and defiant.
 In Down syndrome, language function is a relative weakness, whereas sociability and social skills, such as interpersonal cooperation and conformity with social conventions, are relative strengths.
 Those with Down syndrome also manifest deficiencies in scanning the environment; they are likely to focus on a single stimulus and have difficulty noticing environmental changes.
 A variety of mental disorders occur in persons with Down syndrome, but the rates appear to be lower than those of other mental retardation syndromes, especially autistic disorder.

Psychosocial Syndromes
 A negative self-image and poor self-esteem are common features of mildly and moderately mentally retarded persons, who are well aware of being different from others.
 They experience repeated failure and disappointment in not meeting their parents’ and society’s expectations and in falling progressively behind their peers and even their younger siblings.
 Communications difficulties further increase their vulnerability to feelings of ineptness and frustration. Inappropriate behaviors, such as withdrawal, are common.
 The perpetual sense of isolation and inadequacy has been linked to feelings of anxiety, anger, dysphoria, and depression.

Etiology
 Etiological factors in mental retardation may be primarily genetic, developmental, acquired, or a combination.
 Genetic causes include chromosomal and inherited conditions, developmental factors include prenatal exposure to infections and toxins, and acquired syndromes include perinatal trauma (such as prematurity) and sociocultural factors.
 The severity of the resulting mental retardation of the trauma is related to timing and duration of trauma as well as degree of exposure to the central nervous system.
 The more severe the mental retardation, the more likely it is that the causes is evident.
 Among chromosomal and metabolic disorders, Down syndrome, fragile X syndrome, and phenylketonuria (PKU) are the most common disorders that usually produce at least moderate mental retardation.
 Those with mild mental retardation sometimes have a familial pattern apparent in parents and siblings.
 Deprivation of nutrition, nurturance, and social stimulation may contribute to the development of mental retardation.
 Current knowledge suggest that genetic, environment, biological, and psychosocial factors work additively in mental retardation.

Genetic Factors

 Abnormalities in autosomal chromosomes are associated with mental retardation, although aberrations in sex chromosomes are not always associated with mental retardation (such as Turner’s syndrome with XO and Klinefelter’s syndrome with XXY, XXYY variations).
 Some children with Turner’s syndrome have abnormal to superior intelligence.

Down Syndrome
 Children with this syndrome were originally called mongoloid because of their physical characteristics of slanted eyes, epicanthal folds, and flat nose.
 The problem of cause is complicated even further by the recent recognition of three types of chromosomal aberrations in Down syndrome:

1. Patients with trisomy 21 (three chromosomes, 21s, instead of the usual two) represent the overwhelming majority; they have 47 chromosomes, with an extra chromosomes 21. The mother’s karyotypes are normal. A nondisjunction during meiosis, occurring for known reasons, is held responsible for the disorder.
2. Nondisjunction occurring after fertilization in any cell division results in mosaicism, a condition in which both normal and trisomic cells are found in various tissues.
3. In translocation there is a fusion of two chromosomes, usually 21 and 15, resulting in a total of 46 chromosomes, despite the presence of an extra chromosome 21. The disorder, unlikely trisomy 21, is usually inherited, and the translocated chromosomes may be found in unaffected parents and siblings. The asymptomatic carriers have only 45 chromosomes.

 Persons with Down syndrome tend to exhibit marked deterioration in language, memory, self-care skills, and problem solving in their 30s.

Fragile X Syndrome
 Fragile X syndrome is the second most common single cause of mental retardation.
 The syndrome results from a mutation on the X chromosomes at what is known as the fragile site (Xq27.3).
 The fragile site is expressed in only some cells, and it may be absent in asymptomatic males and females carriers.
 Fragile X syndrome is believed to occur in about 1 in every 1,000 males and 1 in every 2,000 females.
 The typical phenotype includes a large, long head and ears, short stature, hyperextensible joints, and postpubertal macroorchidism.
 The mental retardation ranges from mild to severe.
 The behavioral profile of persons with the syndrome includes a high rate of attention-deficit/hyperactivity disorder, learning disorders, and pervasive developmental disorders, such as autism.
 Deficits in language function include rapid perserverative speech with abnormalities in combining words into phrases and sentences.
 Persons with fragile X syndrome seem to have relatively strong skills in communication and socialization; their intellectual functions seem to decline in the pubertal period.
 Female carriers are often less impaired than males with fragile X syndrome, but females can also manifest the typical physical characteristics and can be mildly retarded.

Prader-Willi Syndrome
 Prader-Willi syndrome is postulated to result from a small deletion involving chromosomes 15, usually occurring sporadically.
 Its prevalence is less than 1 in 10,000. persons with the syndrome exhibit compulsive eating behavior and often obesity, mental retardation, hypogonadism, small stature, hypotonia, and small hands and feet.
 Children with the syndrome often have oppositional and defiant behavior.

Cat’s Cry (Cri-du-Chat) Syndrome
 Children with Cat’s cry syndrome lack part of chromosome 5.
 They are severely retarded and show many signs often associated with chromosomal aberrations, such as microcephaly, low-set ears, oblique palpebral fissures, hypertelorism, and micrognathia.
 The characteristics catlike cry caused by laryngeal abnormalities that gave the syndrome its name gradually changes and disappears with increasing age.


Other Chromosomal Abnormalities
 Other syndromes of autosomal aberrations associated with mental retardation are much less prevalent than Down syndrome.

Phenylketonuria
 The basic metabolic defect in PKU is an inability to convert phenylalanine, an essential amino acid, to paratyrosine because of the absence or inactivity of the live enzyme phenylalanine hydroxylase, which catalyzes the conversion.
 Two other types of hyperphenylalaninemia have recently been described.
 One is due to a deficiency of a cofactor, biopterin.
 The first defect can be detected in fibroblasts, and biopterin can be measured in body fluids.
 Both these rare disorders carry a high risk of fatality.
 Most patient with PKU are severely retarded, but some are reported to have borderline or normal intelligence.
 Eczema, vomiting, and convulsions occur in about a third of all patients.

Rett’s Disorder
 Rett’s disorder is hypothesized to be an X-linked dominant mental retardation syndrome that is degenerated and affects only females.
 Deterioration in communications skills, motor behavior, and social functioning starts at about 1 year of age.
 Autistic like symptoms are common, as are ataxia.
 Facial grimacing, teeth grinding, and loss of speech. Intermittent hyperventilation and a disorganized breathing pattern are characteristic while the child is awake.
 Stereotypical hand movements, including hand wringing, are typical.
 Progressive gait disturbance, scoliosis, and seizures occurs.
 Severe spasticity is usually presented by middle childhood.
 Cerebral atrophy occurs with decreased pigmentation of the substantia nigra, which suggests abnormalities of the dopaminergic nigrostriatal system.

Neurofibromatosis
 Also called von Recklinghausen’s disease.
 Neurofibromatosis is the most common of the neurocutaneous syndromes caused by a single dominant gene, which may be inherited or may be a new mutation.
 Mental retardation occurs in up to one third of those with the disease.

Tuberous Sclerosis
 Tuberous Sclerosis is the second most common of the neurocutaneous syndromes; a progressive mental retardation occurs in up to two thirds of all affected persons.
 Seizures are presented in all those who are mentally retarded and in two thirds of those are not.
 The phenotypic presentation includes adenoma sebaceum and ash-leaf spots that can be identifies with a slit lamp.

Lesch-Nyhan Syndrome
 Lesch-Nyhan syndrome is a rare disorder caused by a deficiency of an enzyme involved in purine metabolism.
 Disorder is X-linked; patients have mental retardation, is also associated with severe compulsive self-mutilation by biting the mouth and fingers.
 Lesch-Nyhan syndrome is another example of a genetically determined syndrome with a specific, predictable behavioral pattern.

Adrenoleukodystrophy
 The most common of several disorders of sudanophilic cerebral sclerosis, adrenoleukodystrophy is characterized by diffuse demyelintion of the cerebral white matter resulting in visual and intellectual impairment, seizures, spascity, and progression of death.
 The clinical onset is generally between 5 and 8 years of age, with early seizures, disturbances in gait, and mild intellectual impairment.
 Abnormal pigmentation reflecting adrenal insufficiency sometimes precedes the neurological symptoms, and attacks of crying are common.
 Spastic contractures, ataxia, and swallowing disturbances are also frequent.
 Although the course is often rapidly progressive, some patients may have a relapsing and remitting course.

Maple Syrup Urine Disease
 The clinical symptoms of maple syrup urine disease appear during the first week of life.
 The infant deteriorates rapidly and has decerebrate rigidity, seizures, respiratory irregularity, and hypoglycemia.
 If untreated, most patient die in the first months of life, and the survivors are severely retarded.
 Some variants have been reported with transient ataxia and only mild retardation.

Other Enzyme Deficiency Disorders
 Several disorders associated with mental retardation have been identified, and still more diseases are being added as new discoveries are made, including Hartnup disease, galactosemia, and glycogen-storage disease.
 Thirty important disorder with inborn errors of metabolism, hereditary transmission patterns, defective enzymes, clinical signs, and relation to mental retardation.

Acquired and Developmental Factors

Prenatal Period
 Important prerequisites for the overall development of the fetus include the mother’s physical, psychological, and nutritional health during pregnancy.
 Maternal chronic illness and conditions affecting the normal development of the fetus’s central nervous system include uncontrolled diabetes, anemia, emphysema, hypertension, and long-term use of alcohol and narcotic substances.
 Maternal infections during pregnancy, especially viral infections, have been known to cause fetal damage and mental retardation.

Rubella (German Measles)
 Rubella has replaced syphilis as the major cause of congenital malformations and mental retardation caused by maternal infection.
 The children of affected mothers may show several abnormalities, including congenital heart disease, mental retardation, cataracts, deafness, microcephaly, and microphthalmia.

Cytomegalic Inclusion Disease
 Cytomegalic inclusion disease remains dormant in the mother. Some children are stillborn, and others have jaundice, microcephaly, hepatosplenomegaly, and radiographic findings of intercerebral calcification.
 Children with mental retardation from the disease frequently have cerebral calcification, microcephaly, or hydrocephalus.

Syphilis
 Syphilis in pregnant women was once the main cause of various neuropathological changes in their offspring, including mental retardation.

Toxoplasmosis
 Toxoplasmosis can be transmitted by the mother to the fetus.
 It causes mild and severe mental retardation and, in severe cases, hydrocephalus, seizures, microcephaly, and chorioretinitis.


Herpes Simplex
 The herpes simplex virus can be transmitted transplacentally, although the most common mode of infection is during birth.
 Microcephaly, mental retardation, intracranial calcification and ocular abnormalities may result.

Acquired Immune Deficiency Syndrome (AIDS)
 Many fetuses of mothers with AIDS never come to term because of stillbirth or spontaneous abortion.
 Of those who are born infected with the human immunodeficiency virus (HIV), up to half have progressive encephalopathy, mental retardation, and seizures within the first year of life. Children born with HIV infection often live only a few years; however, most babies born in HIV-infected mothers are not infected with the virus.

Fetal Alcohol Syndrome
 Fetal alcohol syndrome results in mental retardation and a typical phenotypic picture of facial dysmorphism that includes hypertelorism, microcephaly, short palpebral fissures, inner epicanthal folds, and a short, turned-up nose.
 Often, the affected children have learning disorder and attention-deficit/hyperactivity disorder.
 Cardiac defects are also frequent.
 Babies born to women who consume alcohol regularly during pregnancy have a high incidence of attention-deficit/hyperactivity disorder, learning disorder, and mental retardation without facial dysmorphism.

Prenatal Drug Exposure
 Prenatal exposure to opioids, such as heroin, often results in infants who are small for their gestational age, with a head circumference below the 10th percentile and withdrawal symptoms that appear within the first two days of life.
 The withdrawal symptoms of infants include irritability, hypertonia, tremor, vomiting, a high-pitched cry, and an abnormal sleep pattern.
 Seizures are unusual, but the withdrawal syndrome can be life threatening to infants if it is untreated.

Complications of Pregnancy
 Toxemia of pregnancy and uncontrolled maternal diabetes hazards to the fetus and sometimes result in mental retardation.
 Maternal malnutrition during pregnancy often results in prematurity and other obstetrical complications.
 Vaginal hemorrhage, placenta previa, premature separation of the placenta, and prolapse of the cord may damage the fetal brain by causing anorexia.
 The potential teratogenic effect of pharmacological agents administered during pregnancy was widely publicized after the thalidomide tragedy (the drug produced a high percentage of deformed babies when given to pregnant women).

Prenatal Period
 Some evidence indicates that premature infants and infants with low birth weight are at the risk for neurological and intellectual impairments that appear during their school year.
 Very premature children and those who suffered intrauterine growth retardation were found to be at high risk for developing both social problems and academic difficulties. Socioeconomic deprivation can also affect the adaptive function of these vulnerable infants.
 Early intervention may improve their cognitive, language, and perceptual abilities.

Acquired Childhood Disorder
 Occasionally, a child’s development status changes dramatically as a result of a specific disease or physical trauma.
 In retrospect, it is sometimes difficult to ascertain the full picture of the child’s developmental progress before the insult, but the adverse effects on the child’s development or skills are apparent afterward.

Infection
 The most serious infections affecting cerebral integrity are encephalitis and meningitis.
 Measles encephalitis has been virtually eliminated by the universal use of measles vaccine, and the incidence of other bacterial infections of the central nervous system has been markedly reduced with antibacterial agents.
 Meningitis that was diagnosed late, even when followed by antibiotic treatment, can seriously affect a child’s cognitive development.
 Thrombotic and purulent intracranial phenomena secondary to septicemia are rarely seen today except in small infants.

Head Trauma
 The best-known causes of head injury in children that produces developmental handicaps, including seizures, are motor vehicle accidents, but more head injuries are caused by household accidents, such as fall from tables, from open windows, and on stairways.
 Child abuse is also cause of head injury.



Other Issues
 Brain damage from cardiac arrest during anesthesia is rare.
 One cause of complete or partial brain damage is asphylaxia associated with near drowning.
 Long-term exposure to lead is a well-established cause of compromised intelligence and learning skills.
 Intracranial tumors of various types and origins, surgery, and chemotherapy can also adversely affect brain function.

Diagnosis
 The diagnosis of mental retardation can be made after the history, a standardized intellectual assessment, and a measure of adaptive function indicate that a child’s current behavior is significantly below the expected level.
 The diagnosis itself does not specify the cause or the prognosis.

Clinical Features
 Mild mental retardation may not be diagnosed until the affected children enter school; their social skills and communication may be adequate in the preschool years.
 As they get older, however, such cognitive deficits as poor ability to abstract and egocentric thinking may distinguish them from others of their age.
 Moderate mental retardation is likely to be diagnosed at a younger age than mild mental retardation; communication skills develop more slowly in persons who are moderately retarded, and their social isolation may begin in the elementary school years.
 Children with moderate mental retardation are aware of their deficits and often feel alienated from their peers and frustrated by their limitations.
 Severe mental retardation is generally obvious in the preschool years; affected children’s speech is minima, and their motor development is poor.
 Some languages development may occur in the school-age years.
 Behavioral approaches can help promote some self-care, although those with severe mental retardation generally need extensive supervision.
 Children with profound mental retardation require constant supervision and are severely limited in communication and motor skills.

Course and Prognosis
 In most cases of mental retardation, the underlying intellectual impairment does not improve, yet the affected person’s level of adaptation can be influenced positively by an enriched and supportive environment.
 In general, persons with mild and moderate mental retardation have the most flexibility in adapting to various environmental conditions.

Differential Diagnosis
 By definition, mental retardation must begin before the age of 18. A mentally retarded child has to cope with so many difficult social and academic situations that maladaptive patterns often complicate the diagnostic process.
 Children whose family life provides inadequate stimulation may manifest motor and mental retardation that can be reversed if an enriched, stimulating environment is provided in early childhood.
 Several sensory disabilities, especially deafness and blindness, may be mistaken for mental retardation if no compensation is allowed during testing.
 Children with learning disorders ( which can coexist with mental retardation) experience a delay ior failure to development in a specific area, such as reading, or mathematics, but they develop in other areas.
 In contrast, children with mental retardation show general delays in most areas of development.
 Children under the age of 18 years who meet the diagnostic criteria for dementia and who have an IQ below 70 are given the diagnoses of dementia and mental retardation.
 Those whose IQs drop below 70 after the age of 18 and who have new onsets of cognitive disorders are not given the diagnosis of mental retardation but only the diagnosis of dementia.

Treatment

 The treatment of individuals with mental retardation is based on an assessment of social and environmental needs as well as attention to comorbid conditions.
 The optimal treatment of conditions that could lead to mental retardation is primary, secondary, and tertiary prevention.

Primary Prevention

 Primary prevention concerns actions taken to eliminate or reduce the conditions that lead to development of the disorders associated with mental retardation.
 Such as measures include education to increase the general public’s knowledge and awareness of mental retardation; continuing efforts of health professionals to ensure and upgrade public health policies; legislation to provide optimal maternal and child health care; and eradication of known disorders associated with central nervous system damage.
 Family and genetic counseling helps reduce the incidence of mental retardation in a family with a history of a genetic disorder associated with mental retardation.

Secondary and Tertiary Prevention

 Once a disorder associated with mental retardation has been identified, the disorder should be treated to shorten the course of the illness ( seconday prevention) and to minimize the seqelae or consequent disabilities ( tertiary prevention).
 Mentally retarded children frequently have emotional and behavioral difficulties requiring psychiatric treatment.