31.3 Intellectual Disability
1129
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
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.
