Catalina Cleves Bayon, MD
Gary Hsich, MD
DESCRIPTION 
- Developmental delay is a common problem presenting to pediatricians and family physicians. Children with delayed development are usually identified in the preschool years. This review focuses on conditions that have symptoms affecting cognition and/or language development.
- Developmental delay is a symptom complex and by no means represents a specific diagnosis.
- The term global developmental delay is used when 2 or more domains (language, motor, cognition, social) are affected; it is usually reserved for small children.
- The terms mental retardation and intellectual disability require accurate assessment of intelligence and adaptive skills which may be difficult to accomplish in very young children. Better assessment can be made between 1 and 2 years, when children normally acquire language skills.
- Motor delay is usually noted early in the first year or two of life as a child fails to meet sitting, walking, or other motor milestones.
- Early identification of delay generally implies a more severe disorder of brain development.
EPIDEMIOLOGY
- Mental retardation has an incidence of 1–3%, with the prevalence of mild retardation being inversely related to family socioeconomic status.
- Sex: Twice as many males as females are affected.
RISK FACTORS
Pregnancy Considerations
As a significant percentage of conditions with delayed development are prenatal in origin, the pregnancy history is critical to obtain information related to toxin exposures (fetal alcohol syndrome and illicit drugs), teratogens (anticonvulsant and other medical treatment), infections (TORCH and others), and maternal conditions (diabetes, etc).
ETIOLOGY
- Some children have delayed milestones or exhibit variations from normal. The norms and standard deviations from normal are well documented but, particularly in language development, are variable and broad (e.g., lack of speech development in the hearing child may be acceptable to 2–3 years of age depending on a variety of factors if receptive language is age appropriate).
- More severely affected children are usually recognized in the first year of life, and are somewhat more likely to have an identifiable etiology.
- Disorders of cognition, language, and social development may have many different causes. Nonprogressive pathology affecting the CNS includes fetal insults (in utero infection or toxic exposure), disorders of chromosomal or molecular genetics, and major brain dysgenesis or malformation.
- Prenatal factors (including genetic conditions, neurometabolic disorders, neurocutaneous syndromes, and nonchromosomal dysmorphic syndromes) account for 60–70% of cases. Perinatal problems (prematurity, birth asphyxia, or injury) cause 10%, with postnatal brain injury (meningitis/encephalitis or trauma) being somewhat less than 10%.
- Fragile X syndrome is the most common inherited cause of global developmental delay.
COMMONLY ASSOCIATED CONDITIONS
- Children with developmental delay may present with other disorders affecting brain growth and development.
- Cerebral palsy (CP) is a nonprogressive abnormality of movement and posture. CP can be further characterized by a description of the pattern of abnormality and the affected limbs: Spastic, hypotonic; diplegic, hemiplegic, quadriplegic.
- Seizures can be severe (infantile spasms, Lennox–Gastaut) and may reflect underlying cortical malformations (schizencephaly, lissencephaly/pachygyria, polymicrogyria, heterotopias). Children with both developmental disabilities and epilepsy are less likely to outgrow their seizures, compared to developmentally normal children.
- Autistic spectrum disorders are characterized by impaired language development, abnormal behaviors, and impaired social interactions.
- Vision impairment may occur in up to 50%, while hearing impairment may affect 18% of these patients. Treatment of these conditions may significantly affect developmental outcomes.
- Other commonly associated conditions are attention deficit and hyperactivity disorders.
[Outline]
- Thorough history taking should be done to determine which developmental areas are affected and to estimate the child's actual developmental age and to compare it with the chronological age. The comprehensive evaluation of the child's current level of functioning should include physical motor, cognitive, communication (speech and language), and social and play development.
- The pregnancy history may reveal risk factors for poor fetal growth and development. Growth measurements, particularly head circumference, are invaluable in assessing a child who has failed to thrive or has micro- or macrocephaly.
- Additional medical history may help narrow the differential diagnosis into a specific syndrome.
- It may be useful to ask parents to bring photographs or videotapes that demonstrate previous developmental skills, especially if there is true developmental regression and loss of milestones.
- Family history must be reviewed in detail; it is essential to complete a three-generation pedigree.
- A good social history should be taken to identify any potential psycho-socio-economic contributors to the etiology.
- Physical examination is focused on detection of dysmorphic features, and other organ or system involvement. Head circumference measurements should be done; if abnormal in the index patient, parental head circumference measurements should also be included. Particular attention should be paid to the presence or absence of abnormal growth parameters, pigmentary retinopathy, organomegaly, neurocutaneous lesions, and any dysmorphic features. Findings on physical exam may help localize the abnormalities to the CNS, or to the periphery (such as peripheral nerve or muscle).
DIAGNOSTIC TESTS AND INTERPRETATION
Lab
- There is no consensus on the choice of diagnostic investigations for developmental delay. The decision to perform diagnostic imaging and laboratory procedures is based on the comprehensive historical and physical examination described above. In addition to the diagnostic yield of any given test, other factors to consider include the ability of a test to identify a treatable disorder; invasiveness; and cost of testing. The potential diagnostic yield can be greatly improved by careful and thoughtful consideration of the medical history and physical exam. However, many etiologies cannot be definitively proven or disproven (such as unknown genetic disorders or toxin exposures).
- The following investigations may be considered in the initial evaluation:
- Microarray studies are an evolving technology and have the highest diagnostic yield of currently available genetic tests. The diagnostic yield of a microarray ranges from 5% to 10%, but can be greatly increased in certain situations such as dysmorphisms, congenital anomalies, or more severe neurological impairments.
- If a specific diagnosis is suspected based on examination findings, directed testing (such as Down’s, Fragile X, Rett, or Prader–Willi) should be pursued.
- Routine metabolic screening has a yield between 0.2% and 4.6%, depending upon associated clinical features and specific testing performed. Some tests (such as lactate and ammonia) are nonspecific and notoriously subject to technical factors. Therefore, metabolic testing should be carefully and selectively performed. Higher yield situations include consanguineous parents, siblings with similar symptoms, early childhood deaths, multiple organ system dysfunction, unusual odors, or dietary selectivity.
- Some of these tests are:
- Serum amino acids, lactate, ammonia, very-long-chain fatty acids, congenital disorders of glycosylation
- Urine organic acids, oligosaccharides, and mucopolysaccharides
- Other considerations:
Imaging
Brain MRI may identify abnormalities in 48–65% of patients.
Neurophysiology
Electroencephalogram is indicated if there is realistic concern for seizures. Otherwise, the diagnostic yield in patients with developmental delay is <1% in the absence of symptoms suggestive of seizures.
Diagnostic Procedures/Other
- Audiologic and ophthalmologic evaluation should be performed in all children with developmental delay, as treatment of these disorders will impact developmental outcome.
- Children with developmental delay also need neuropsychological evaluation. Program recommendations and current level functioning are provided by educational, speech, physical, and occupational therapy assessment.
DIFFERENTIAL DIAGNOSIS
- Developmental delay/mental retardation must be distinguished from primary speech and language disorders and autistic spectrum conditions. Children with isolated motor delays require evaluation for neuromuscular disorders (muscular dystrophy, congenital myopathies).
- Broad categories of etiologic diagnosis include malformations of brain development, prenatal infections, or exposure and neurogenetic disorders.
- A careful history is necessary to distinguish delayed development from disorders in which there is a loss of acquired skills and developmental regression (the neurodegenerative disorders of childhood).
[Outline]
Interventions
Early intervention with speech, occupational, and physical therapy is the cornerstone of treatment of children with developmental disabilities. The goal is to maximize their developmental potential. Any visual or hearing impairment should be addressed and optimized.
MEDICATION
- There are no specific pharmacologic treatments for children with developmental delay, although if situations arise when behavioral management methods fail, then psychotropic medication options can be cautiously considered.
- Alternative drugs: There are no evidence-based studies to support the use of alternative treatment methods.
ADDITIONAL TREATMENT
General Measures
As there are many diverse origins for developmental disorders, management is based on thorough assessment and program planning; for example, the child with an isolated speech delay requires audiologic evaluation, communication testing, and focused speech and language treatment programming.
COMPLEMENTARY AND ALTERNATIVE THERAPIES
- Symptomatic treatment
- General treatment and rehabilitation measures are necessary following assessment recommendations, with educational programming provided in structured classroom environment for the older children.
- The multidisciplinary team approach is considered the most comprehensive assessment and treatment model. Management is usually best arranged and supervised at a special children's treatment center.
- Genetics
- Ophthalmology
- Audiology
- Adjunctive treatment
- Parents who have children with developmental disorders may be assisted in caring for their child through the provision of a variety of nonmedical services, for example, behavioral counseling and respite care.
[Outline]
FOLLOW-UP RECOMMENDATIONS
Patient Monitoring
- After a comprehensive diagnostic evaluation and arrangements made for developmental and rehabilitation treatment carried out by appropriate members of the multidisciplinary team, medical follow-up can focus on general monitoring of expected progress in providing anticipatory counseling. Such issues as the need for formal genetic counseling (in defined disorders) and assessment for requirement for medication intervention with behavioral problems may need to be addressed.
- In cases in which no specific diagnosis is made, a thoughtful tailored reinvestigation should be conducted every 2–3 years.
PATIENT EDUCATION
Parents of children who have a defined developmental diagnosis should be referred to the appropriate family association and provided with a list of Internet resources.
[Outline]
