Developmental Disabilities
Patty Huang
INTRODUCTION
When caring for children with developmental disabilities, the physician must consider possible causes for the disorder, screening for problems associated with the disorder, and interventions to minimize functional impairment and prevent long-term complications.
CEREBRAL PALSY
Definition and Etiology
Cerebral palsy (CP) is a nonprogressive disorder of motion and posture that results from injury to the developing central nervous system. It occurs in 1.5 to 2.5 children per 1,000 live births. Prematurity is the single most significant risk factor; approximately 8% to 10% of infants with a birth weight >1,500 g develop CP. Although perinatal asphyxia was once thought to be a major cause of CP, it is now thought to cause > 10% of cases. A genetic abnormality can be identified in about 10% of cases and is more likely to be found in a term infant with CP than a preterm infant. In approximately 15% to 20% of patients, no cause can be identified.
Classification
Spastic. This form of CP is characterized by increased deep tendon reflexes and increased muscle tone with a “clasp knife” quality (i.e., initially, resistance to movement is strong but then the muscle gives way suddenly). It can be further subclassified based on the limbs that are involved:
Hemiplegia: Involves both the arm and the leg on either the left or the right side of the body.
Quadriplegia: Significant impairment in all four extremities.
Diplegia: Bilateral leg involvement; arms may have mild impairment.
Extrapyramidal. The most common form of extrapyramidal CP is choreoathetoid CP, which is characterized by sudden involuntary movements of the extremities. Muscle tone is variable within the individual over time. The resistance to movement is described as “lead pipe” rigidity (i.e., persistent pressure results in slow movement of the limb).
Mixed. Components of both spastic and choreoathetoid CP are present.
Associated Problems
Cognitive deficits—mental retardation (50%) and learning disabilities.
Speech and language deficits—communication disorders and dysarthria.
Sensory deficits—visual impairment, strabismus, and hearing impairment.
Gastrointestinal problems—oral-motor dysfunction, gastroesophageal reflex disease, and constipation.
Urinary tract problems—spastic bladder and recurrent urinary tract infection.
Neurologic problems—spasticity and seizures.
Musculoskeletal problems—joint contractures, dislocated hips, and scoliosis.
Psychosocial and behavioral problems.
HINT: Multiple methods are available for managing spasticity and preventing or managing contractures for individuals with spastic CP, including physical therapy and positioning, oral medications (e.g., baclofen, dantrolene, and diazepam), botulinum toxin injections, intrathecal baclofen, and surgery (e.g., tendon lengthening and dorsal rhizotomy).MYELOMENINGOCELE
Definition and Etiology
A myelomeningocele is a sac containing meninges and a malformed spinal cord that protrudes through defective vertebrae (in contrast, a meningocele is a sac containing only meninges; the spinal cord is normal).
Myelomeningoceles develop ˜ 28 days after conception if the neural tube fails to close. The incidence varies with ethnicity and geography and ranges from one to five per 1,000 live births. The cause of this defect is not known, but both environmental exposures and genetic factors are important. Maternal oral folic acid supplementation prior to conception and throughout the first trimester reduces the risk of myelomeningocele by 50% to 70%. The risk of recurrence in the family of a child with a myelomeningocele is 15 to 30 times higher than in the general population; myelomeningocele may also occur in association with a chromosomal abnormality.
Classification
The level of the lesion is predictive of the degree of functional impairment. Difficulties with bowel and bladder function occur with virtually all lesions.
Thoracic lesions—flaccid paralysis of both lower extremities with weakness of the trunk musculature
L1 to L2 lesions—flaccid paralysis of the knees, ankles, and feet with voluntary hip flexion and adduction
L3 lesions—same as L1 to L2 lesions, but knee flexion is present as well
L4 to L5 lesions—knee flexion and extension and ankle dorsiflexion are present, but plantar flexion and hip extension are weak or absent
Sacral lesions—mild weakness of ankles and toes
Associated Problems
The degree and type of associated problems are also related to the level of the lesion.
Cognitive deficits—mental retardation (33%) and learning disabilities
Neurologic problems—hydrocephalus (70% to 80%) and Arnold-Chiari deformity (type II)
Urinary tract problems—incontinence, recurrent urinary tract infection, vesicoureteral reflex, and kidney damage
Bowel dysfunction—incontinence and constipation
Musculoskeletal disorders—scoliosis and hip dislocation
Sexual dysfunction—partial erection and retrograde ejaculation
Ophthalmologic disorders—strabismus
Dermatologic disorders—decubitus ulcers
HINT: At a few centers, fetal surgery to close the myelomeningocele is being done late in the second or early in the third trimester of the pregnancy. Although results are preliminary, this type of surgery seems to have the potential to decrease the neurologic impairment.INTELLECTUAL DISABILITY (FORMERLY KNOWN AS MENTAL RETARDATION)
Definition and Etiology
Intellectual disability (ID) is defined as “significant limitations in both intellectual functioning and adaptive behavior expressed in conceptual, social, and practical adaptive skills and age of onset before the age of 18” (American Association on Intellectual and Developmental Disabilities, Washington, DC, 2010).
HINT: Intellectual disability cannot be diagnosed from an intelligence test alone. The individual must also have a deficit in adaptive behavior.The likelihood of identifying the cause of a patient’s ID depends on the severity of the disability. A cause can be identified in ˜50% of patients with mild ID, and in 80% of patients with severe or profound ID. Chromosomal abnormalities (e.g., Down syndrome and fragile X syndrome) are the most commonly identified causes of ID. Other causes of ID include perinatal or postnatal injury, teratogens (e.g., fetal alcohol syndrome), intrauterine infection, and inborn errors of metabolism.
Classification
Descriptions of an individual’s strengths, weaknesses, and the level of support needed (intermittent, limited, extensive, or pervasive) are most helpful in planning for educational/vocational, social/recreational, and daily living needs.
IQ-based subclassifications are often used but are not as helpful for intervention planning.
IQ-based subclassifications are often used but are not as helpful for intervention planning.
Mild ID: IQ 50-55 to ˜70
Moderate ID: IQ 35-40 to 50-55
Severe ID: IQ 20-25 to 35-40
Profound ID: IQ below 20-25
HINT: For IQ scores in the ranges that overlap between subclassifications, the individual’s adaptive functioning should be used to determine the appropriate subclassification.
HINT: Developmental testing results in the toddler and preschool years are often described as a development quotient (DQ) as opposed to an IQ. A DQ equals the mental age divided by the chronological age, multiplied by 100. For example, a 4-year-old functioning at a 2-year-old level would have a DQ of 50.Associated Problems
For children with a specific syndrome, the associated problems are related to the syndrome. In general, children with ID are at increased risk for hearing or visual deficits, which occur in up to 25% of children with mild ID and in >50% of children with severe ID. Seizures and behavior problems ranging from hyperactivity to self-injury occur with increased frequency in this population.
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