Kaplan + Sadock's Synopsis of Psychiatry, 11e

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31.3 Intellectual Disability

extremities may offer clues for particular syndromes. The cir- cumference of the head should be measured as part of the clini- cal investigation. Dermatoglyphics may offer another diagnostic tool, because uncommon ridge patterns and flexion creases on the hand are often found in persons who are intellectually dis- abled. Abnormal dermatoglyphics occur in chromosomal disor- ders and in persons who were prenatally infected with rubella. Table 31.3-4 lists syndromes with intellectual disability and their behavioral phenotypes. Neurological Examination Sensory impairments occur frequently among persons with intellectual disabilities. For example, hearing impairment occurs in 10 percent of persons with intellectual disability, a rate that is four times that of the general population. Visual disturbances can range from blindness to disturbances of spa- tial concepts, design recognition, and concepts of body image. Seizure disorders occur in about 10 percent of intellectually disabled populations and in one third of those with severe intellectual disability. Neurological abnormalities increase in incidence and severity in direct proportion to the degree of intellectual disability. Disturbances in motor areas are mani- fested in abnormalities of muscle tone (spasticity or hypo- tonia), reflexes (hyperreflexia), and involuntary movements (choreoathetosis). Less disability may also be associated with clumsiness and poor coordination. Clinical Features Mild intellectual disability may not be recognized or diagnosed in a child until school challenges the child’s social and commu- nication skills. Cognitive deficits include poor ability to abstract and egocentric thinking, both of which become more easily evi- dent as a child reaches middle childhood. Children with milder intellectual disabilities may function academically at the high elementary level and may acquire vocational skills sufficient to support themselves in some cases; however, social assimilation may be problematic. Communication deficits, poor self-esteem, and dependence may further contribute to a relative lack of social spontaneity. Moderate levels of intellectual disability are significantly more likely to be observed at a younger age, since communica- tion skills develop more slowly and social isolation may ensue in the elementary school years. Academic achievement is usually limited to the middle-elementary level. Children with moderate intellectual deficits benefit from individual attention focused on the development of self-help skills. However, these children are aware of their deficits and often feel alienated from their peers and frustrated by their limitations. They continue to require a relatively high level of supervision but can become competent at occupational tasks in supportive settings. Severe intellectual disability is typically obvious in the preschool years; affected children have minimal speech and impaired motor development. Some language development may occur in the school-age years. By adolescence, if language has not improved significantly, poor, nonverbal forms of commu- nication may have evolved. Behavioral approaches are useful means to promote some self-care, although those with severe intellectual disability generally need extensive supervision.

whereas the Kaufman Adolescent and Adult Intelligence Test is applicable to a wide range of ages, from 11 to 85 years. All of the above standardized instruments evaluate cognitive abilities across multiple domains including verbal, performance, mem- ory, and problem solving. Standardized instruments measuring adaptive function (functions of “everyday” life) are based on the construct that adaptive skills increase with age, and that adap- tation may vary across different settings such as school, peer relationships, and family life. The Vineland Adaptive Behavior Scales can be used in infants through youth 18 years of age and includes four basic domains including Communication (Recep- tive, Expressive, and Written); Daily Living Skills ( Personal, Domestic, and Community); Socialization (Interpersonal Rela- tions, Play and Leisure, and Coping Skills); Motor Skills (Fine and Gross). Several behavioral rating scales have been developed for the population with intellectual disability. General behavioral ratings scales include the Aberrant Behavior Checklist (ABC) and the Developmental Behavior Checklist (DBC). The Behav- ior Problem Inventory (BPI) is a good screening instrument for self-injurious, aggressive, and stereotyped behaviors. The Psy- chopathology Inventory for Mentally Retarded Adults (PIMRA) is utilized to identify the presence of comorbid psychiatric symptoms and disorders. Examining clinicians can use several screening instruments for developmental and intellectual delay or disability in infants and toddlers. However, controversy over the predictive value of infant psychological tests is heated. Some report the correlation of abnormalities during infancy with later abnormal functioning as very low, and others report it to be very high. The correlation rises in direct proportion to the age of the child at the time of the developmental examination. Some exercises such as copy- ing geometric figures, the Goodenough Draw-a-Person Test, the Kohs Block Test, and geometric puzzles all may be used as quick screening tests of visual-motor coordination. The Gesell and Bayley scales and the Cattell Infant Intelligence Scale are most commonly used with infants. The Peabody Vocabulary Test is the most widely used vocab- ulary test solely based on pictures. Other tests often found use- ful in detecting intellectual disability are the Bender Gestalt Test and the Benton Visual Retention Test. The psychological evalu- ation should assess perceptual, motor, linguistic, and cognitive abilities. Physical Examination Various parts of the body may demonstrate identifying charac- teristics of specific perinatal and prenatal events or conditions associated with intellectual disabilities. For example, the con- figuration and the size of the head may offer clues to a variety of conditions, such as microcephaly, hydrocephalus, or Down syndrome. A patient’s facial characteristics, for example, hyper- telorism, a flat nasal bridge, prominent eyebrows, epicanthal folds may provide clues to a recognizable syndrome such as FAS. Additional facial characteristics including corneal opaci- ties, retinal changes, low-set and small or misshapen ears, a pro- truding tongue, and disturbance in dentition may be stigmata of a variety of known syndromes. Facial expression, color and texture of the skin and hair, a high-arched palate, the size of the thyroid gland, and the proportions of a child’s trunk and