Brian T. Maurer
The ability to perform a thorough toddler developmental assessment is an essential skill that needs to be cultivated by all pediatric healthcare providers. Particularly disturbing is the child who isn’t beginning to talk, because language development provides a window that reflects cognitive development. The provider needs to identify problems as early as possible in order to begin necessary interventions. The farther behind the child becomes, the more difficult it will be to bring him or her into the normal range again because normal children are progressing rapidly at this time. Currently, children with language and social delays are appearing all too often in primary care practices, and many parents are frightened of the possibility of autism as a diagnosis for their once normal-appearing child whose language is now delayed.
1. Review the developmental milestones for toddlers.
2. Describe the screening and assessment strategies to identify a child with language and social delays and a child who needs to be screened for autism.
3. Describe the primary care provider’s role in coordination of services and family support for children with autism or other developmental delays.
Case Presentation and Discussion
Ms. Jones brings her twin boys into the office for their 18-month well child visit. Peter and James are fraternal twins, born vaginally at 36 weeks gestation. To date, with the exception of several minor colds, both boys have enjoyed good health. A quick review of the records shows that both boys have grown well, although Peter ranks slightly higher in his growth parameters (height, weight, and head circumference) than James.
You greet Ms. Jones as you enter the exam room and begin to explore the boys’ developmental progress with several open-ended questions, knowing that developmental surveillance is a recommended part of all well child visits, especially at the 9-, 18-, and 30-month visits. Furthermore, you are aware of the American Academy of Pediatrics’ recommendations to use an autism-specific screen at the 18-month visit (American Academy of Pediatrics [AAP], 2006).
Toddler and Preschooler Development
What specific developmental milestones should be sought out at the 18-month visit?
Speech and expressive language skills begin to emerge by 15 months of age. Most toddlers engage in active jargoning, laying down underlying speech patterns through vocal inflection and intonation, by their first birthday. In addition, many 15-month-olds use the words “dada” and “mama” specifically to indicate their father and mother, as well as three other words. They also engage in verbal play, pointing to body parts when named and producing animal sounds when asked. The child with no documented expressive speech at 16 months of age is delayed in this area. By 18 months of age, most toddlers will have a vocabulary of 15–20 words. Additional developmental milestones are delineated in Table 3-1.
Given that these twins are fraternal, would you expect to find any marked differences in their development?
Fraternal twins, like other siblings, may demonstrate considerable variation in achieving developmental milestones but the variation should be within the range of normal milestones.
Information About Autistic Spectrum Disorders and Language Delays
Autistic spectrum disorders (ASDs) are neurodevelopmental disorders in which children exhibit a lack of age-appropriate personal-social, adaptive, and communication skills. Children with ASDs demonstrate restricted interests, perseverative behaviors with repetitive activities, and qualitative impairments in sharing interests and enjoyment with others. Insistence on maintaining nonfunctional routines and rituals in daily life are additional hallmarks of these disorders.
Pervasive developmental disorder, not otherwise specified (PDD-NOS) is considered to be a subthreshold diagnosis where the young child exhibits characteristics of autism disorder (AD) but fails to meet the strict criteria to allow a formal diagnosis of AD (Figure 3-1).
Asperger syndrome (AS) is a form of AD found in older children. Children with AS do not exhibit the same degree of speech and language problems as children with AD or PDD-NOS.
Table 3–1 Developmental Milestones for Toddlers 18 Months of Age
I. Gross motor
Runs and climbs well
Walks up steps
Climbs into adult chair
II. Fine motor
Uses a spoon and cup
Stacks three or more blocks
Drinks from a cup with little spilling
Actively engages in social interaction
Shows fear, anger, affection, and jealousy
Able to say 15–20 words clearly
Uses two-word phrases and imitates words
Follows two-step commands (18–24 months)
Vocabulary increasing (18–24 months)
Enjoys simple stories (18–24 months)
Recognizes pronouns (18–24 months)
To date, the etiology of ASDs remains elusive. Researchers have postulated that genetic (Muhle, Trentacoste, & Rapin, 2004) and, to a lesser extent, environmental influences play a role. It is highly likely that the etiology is multifactorial (Barbaresi, Katusic, & Voight, 2006).
The prevalence of ASDs has increased 10-fold over the past several decades. Earlier studies demonstrated a prevalence of 1 in 2,000; recent figures show a frequency of 1 in 150 (Autism and Developmental Disabilities Monitoring Network, 2007), with males outnumbering females by a ratio of 3.5 to 1. With these odds, it is likely that most clinicians will diagnose or follow a child with ASD in the primary care setting.
A timely diagnosis is imperative for successful intervention for the child with ASD.
A. A total of six (or more) items from (1), (2), and (3), with at least two from (1), and one each from (2) and (3):
(1) Qualitative impairment in social interaction, as manifested by at least two of the following:
(a) Marked impairment in the use of multiple nonverbal behaviors such as eye-to-eye gaze, facial expression, body postures, and gestures to regulate social interaction
(b) Failure to develop peer relationships appropriate to developmental level
(c) Lack of spontaneous seeking to share enjoyment, interests, or achievements with other people (e.g., by a lack of showing, bringing, or pointing out objects of interest)
(d) Lack of social or emotional reciprocity
(2) Qualitative impairments in communication as manifested by at least one of the following:
(a) Delay in, or total lack of, the development of spoken language (not accompanied by an attempt to compensate through alternative modes of communication such as gesture or mime)
(b) In individuals with adequate speech, marked impairment in the ability to initiate or sustain a conversation with others
(c) Stereotyped and repetitive use of language or idiosyncratic language
(d) Lack of varied, spontaneous make-believe play or social imitative play appropriate to developmental level
(3) Restricted repetitive and stereotyped patterns of behavior, interests, and activities, as manifested by at least one of the following:
(a) Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus
(b) Apparently inflexible adherence to specific, nonfunctional routines or rituals
(c) Stereotyped and repetitive motor mannerisms (e.g., hand or finger flapping or twisting, or complex whole-body movements)
(d) Persistent preoccupation with parts of objects
B. Delays or abnormal functioning in at least one of the following areas, with onset prior to age 3 years: (1) social interaction, (2) language as used in social communication, or (3) symbolic or imaginative play.
C. The disturbance is not better accounted for by Rett Disorder or Childhood Disintegrative Disorder
Source: From Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Text Revision (DSM-IV-TR). Washington DC: American Psychiatric Association; 2000:75. Retrieved at http://www.cdc.gov/ncbdd/autism/overview_diagnostic_criteria.htm
Figure 3-1 Diagnostic criteria for 299.00 autistic disorder.
Data for the Diagnosis
Peter has developed several words: he says “dada” and “mama,” as well as “ball,” “baba” (bottle), and “juice.” He also points or gestures to indicate his wants. James, on the other hand, has no discernible words. Many times he screams when he wants something. Ms. Jones admits that she finds it frustrating to figure out what James wants. She asks for advice on how to stimulate James’s speech.
How would you respond to Ms. Jones’s question?
You acknowledge Ms. Jones’s frustration and offer your support. You tell her that before offering advice on how to stimulate James’s speech, you need to obtain additional information about other areas of his development.
What additional questions could be asked to get a better handle on James’s language development?
You ask Ms. Jones to what extent James seems to understand her when she talks to him. She reports that many times he will just stand and look at her briefly when she speaks to him, then resume his activity without further acknowledgement. Sometimes he doesn’t seem to respond when she calls him by name.
Does James meet the criteria for a language delay?
By parental report, James meets the criteria for developmental delay in both expressive speech and receptive language. Not only is he not using simple words to express his desires, but he also demonstrates a lack of comprehension and engagement when others speak to him.
What other concerns arise with this new piece of information?
Adequate hearing discrimination is necessary for proper speech development. A child cannot learn to mimic speech sounds that he cannot hear. Thus, it is vitally important to ascertain the child’s ability to hear, especially at the level of speech frequencies.
An additional concern is that James responds inconsistently when called by name. Ms. Jones reports that sometimes James seems to respond to sounds. For example, he runs to the telephone when it rings and stares at the receiver. He also responds to the doorbell. He watches the television for brief periods of time. Meantime, you flip back through James’s chart and verify that he passed his newborn hearing screen evaluation. You also note that James has had no middle ear infections to date.
During conversation with their mother, you have a chance to observe Peter and James as they move about the exam room. Peter has pulled a number of books from the plastic basket in the corner. He opens one, flips through the pages briefly, then brings the book to his mother, pulling on her skirt and holding the book up for her to see. “Oh, you’ve found a book to read!” Ms. Jones says that “Peter likes books.” You note that James is sitting on the floor holding a toy car upside down. He spins the wheels repeatedly with one hand over and over again. When you comment on this behavior, Ms. Jones concurs that James frequently engages in such play at home. “He’s mesmerized by a music box carousel that spins round and round,” she tells you. Another favorite toy is a pinwheel.
Armed with these data, what additional areas of development should be explored?
Although clinical observations support age-appropriate fine motor skills, there are concerns with James’s social development (i.e., how he relates to others). Other developmental skills, such as adaptive and gross motor parameters, should be documented as well. Interest in and perseveration with spinning objects such as pinwheels are behaviors commonly associated with autistic children.
You ask Ms. Jones about James’s sociability. Does he like to cuddle? Will he blow kisses? Is he averse to being held? Is there any interactive play with his brother?
Ms. Jones reports that James has never been a cuddler. Even as an infant, when he would cry for hours, he refused to be consoled. “We thought he had the colic,” she says. “I was always so thankful when he would finally fall asleep. I know they’re twins, but James was always so different from his brother.” Ms. Jones also reports that James prefers playing with common objects by himself. “It’s almost as if he were in his own little world most of the time,” she comments.
Ms. Jones states that both boys began to walk independently by 15 months of age. They are very active physically and now climb the stairs at home. Mealtimes have become a chore, because both boys refuse to allow their mother to feed them. They insist on feeding themselves, although they are quite messy. They can hold a spoon and drink from a cup, but Ms. Jones states that they still need a bedtime bottle for comfort.
What additional information do you need to gather to continue your assessment of James?
You continue to search for relevant data by developing the family, social, and environmental history.
Ms. Jones is 36 years of age and has no medical problems. She left her secretarial position one month before the twins were born to devote herself to rearing them. She has been married for 5 years and describes her husband as a supportive spouse and involved father. He looks forward to interacting with the children when he returns home from work. They reside in a relatively new single family home. No other blood relatives in the extended family have been diagnosed with epilepsy, mental retardation, or genetic syndromes.
It is now time to proceed with the physical examination. Examining a toddler is often a challenging task for the healthcare provider. Many children will actively struggle during the examination at this age. Peter and James are no exceptions.
During your approach to the children, you notice that James seems to be particularly averse to touch. He recoils at the slightest attempt to soothe him through subdued interaction. At one point, James seems to be more interested in your stethoscope than in any personal interaction. He screams when held for the otoscopic exam. You note that both ear canals are patent with mobile glistening grey tympanic membranes. His palate is intact. There are no hypopigmented lesions on the skin. Neurologically, he exhibits symmetrical muscle tone and strength. You note no dysmorphic features. On the contrary, James appears to be a beautiful little boy.
At this point, you are considering possible diagnoses for the abnormal development you are identifying in this little boy.
Making the Diagnosis
What specific differential diagnoses should be considered at this juncture, given this constellation of symptoms?
• Primary language delay, with associated behavioral issues.
• Additional developmental delays in the personal-social and adaptive categories may indicate mental retardation.
• Emerging autistic spectrum disorder: pervasive developmental disorder, NOS.
What other diagnoses would be considered but are of less likelihood in this case?
The clinician may consider other diagnoses delineated in Box 3-1. Given the clinical presentation at hand, these are much less likely.
At this point James exhibits several “red flags” on the list of concerns indicating the possibility of autistic spectrum disorder:
• No babbling by 12 months of age
• No pointing or gesturing to indicate wants by 12 months of age
• No single words documented by 16 months of age
• No spontaneous two-word combinations (usually seen by 24 months of age)
• Loss of language or social skills at any age
Box 3–1 Differential diagnosis for autism.
• Neuro-psychological disorders
• Elective mutism
• Obsessive-compulsive disorder
• Schizophrenia of childhood
• Conduct disorder
• Mental retardation
• Neurological disorders
• Absence seizures
• Tourette syndrome
• Hearing impairment
• Lead poisoning
• Fetal alcohol syndrome
• Genetic conditions
• Tuberous sclerosis (3–4% of autism cases) (Barbaresi et al., 2006).
• Fragile X (7% of autism cases) (Barbaresi et al., 2006).
• Rett syndrome
• Cornelia de Lange syndrome
• Down syndrome
• Angelman syndrome
• Smith-Magenis syndrome
• Inborn errors of metabolism (5% of autism cases) (Barbaresi et al., 2006).
James also exhibits several early warning signs of autistic spectrum disorder:
• Extremes of temperament and behavior (marked irritability to alarming passivity)
• Lack of meaningful social eye contact
• Inconsistent orienting to his name
• Lack of joint attention
• Lack of motor and expressive reciprocation
• Lack of reciprocation to sounds
• Lack of interactive play
Joint attention, a normal behavior that occurs spontaneously in young children, is manifested as apparent enjoyment in sharing an experience with another person. A deficit in joint attention skills is an important diagnostic clue for ASD in the very young child.
What diagnoses were ruled out through your physical examination?
Normal-appearing tympanic membranes suggest the absence of conductive hearing loss, although this finding does not rule out sensorineural loss. The absence of ash leaf spots or café au lait macules make neurocutaneous disorders less likely. A normal neurological examination and absence of dysmorphic features point away from fetal alcohol syndrome or a genetic aberration, such as Down syndrome.
Other Tests for the Diagnosis
At this point, what additional testing is indicated to arrive at a diagnosis?
• Recheck the child’s head circumference. Twenty-five percent of autistic children exhibit macrocephaly.
• Despite the mother’s report and your documentation of normal tympanic membranes, a formal audiological evaluation is warranted to rule out a hearing problem (Filipek et al., 2000).
• Lead testing is indicated if not done previously (Filipek et al.).
• Various screening tools are available to assist the clinician in further evaluation of the child suspected of having an autistic spectrum disorder, such as the Pervasive Developmental Disorder Screening Test (PDDST-II) (Siegel, 2004a, 2004b), Checklist for Autism in Toddlers (CHAT) (Baird et al., 2000), and the Modified Checklist for Autism in Toddlers (M-CHAT) (Robins, Fein, Barton, & Green, 2001). These questionnaires are designed to be completed by the parent and subsequently scored by the clinician. The CHAT includes additional clinical observation questions. In the M-CHAT (Figure 3-2), critical items indicative of autism include:
Lack of response when called by name
Lack of imitation/reciprocation
Failure to “follow a point”
Lack of pointing to indicate interest
Lack of interest in other children
Lack of bringing objects over to parent to “show”
What additional diagnostic testing might be considered?
Although routine screening for ASDs in the primary care setting is based on clinical observation, laboratory investigation may be warranted given the child’s presentation. More sophisticated testing, if indicated, is usually initiated by a pediatric specialist (e.g., a pediatric neurologist, psychiatrist, geneticist, or developmental pediatrician) (Filipek et al., 2000).
Source: © 1999 Diane Robins, Deborah Fein, & Marianne Barton. Used with permission.
Please refer to Robins, D., Fein, D., Barton, M., & Green, J. (2001). The Modified Checklist for Autism in Toddlers: An initial study investigating the early detection of austism and pervasive developmental disorders. Journal of Autism and Developmental Disorder, 31(2), 131–144.
Note. The Modified Checklist for Autism in Toddlers (M-CHAT) and supplemental materials are available for free download for clinical research and educational purposes. There are two authorized Web sites that these materials can be downloaded from: www.firstsigns.org and www2.gsu.edu/~wwwpsy/faculty/robins.htm. Users should be aware that the M-CHAT continues to be studied and may be revised in the future. Any revisions will be posted to the two Web sites noted above. The M-CHAT must be used in its entirety. There is no evidence that using a subset of items will be valid.
Figure 3-2 Modified Checklist for Autism in Toddlers (M-CHAT).
Were James to meet the criteria for global developmental delays and mental retardation (GDD/MR), high-resolution chromosome analysis and DNA for fragile X testing would be indicated. Seven to eight percent of children with ASD test positive for fragile X (Muhle et al., 2004).
In children with cyclic vomiting, unusual odor, regression of skills, or dysmorphic features, selective metabolic testing may be considered. In the absence of seizure activity or focal neurological signs, routine EEG and neuroimaging are not indicated.
Many times children suspected of having an ASD are referred to a pediatric developmental specialist for further evaluation.
You express your concerns about James’s development to Ms. Jones and suggest that further testing be done. She concurs.
Diagnostic and Intervention Plan
The results of laboratory testing and audiological screening are within normal limits. You refer James to a developmental pediatrician. As part of his evaluation, a Childhood Autism Rating Scale (CARS) (Schopler, Reichler, DeVellis, & Daly, 1980) is administered. Numerical values are assigned given the child’s performance on this 15-item assessment tool. A score above 30 on the CARS is suggestive of an autistic spectrum disorder. On the basis of the specialist’s assessment, James’s profile falls into the category of autistic spectrum, meeting the criteria for autism disorder. Placement in an early intervention program specializing in children with autistic spectrum disorders is recommended. Fortunately, the family’s local school district has an excellent center that specializes in children with this disorder.
Educational interventions form the basis for management of children with ASDs. The sooner the intervention is initiated, the better the outcome. Children with ASDs should be actively engaged in an intervention program at least 25 hours per week throughout the calendar year (Myers & Johnson, 2007).
Specific methodologic programs include Applied Behavior Analysis (ABA), highly structured comprehensive early intervention programs, and functional behavior analysis. ABA methods are designed to shape desirable adaptive behaviors, and their effectiveness has been well documented (Barbaresi et al., 2006; Myers & Johnson, 2007). The Treatment and Education of Autistic and Related Communication-Handicapped Children (TEACCH) program emphasizes structured teaching and environmental modification to improve skills of individuals with ASDs.
Other appropriate interventions include speech and language therapy, social skills instruction, and occupational therapy. Primary care providers play a vital role in advocating these services for the child with an ASD as well as the child’s need for continuing participation in programs for autistic children throughout childhood.
One month later Ms. Jones telephones your office to ask what caused James’s autism. She is particularly concerned about the vaccines both boys received and whether they should continue to receive any additional vaccines. She heard on the news that some vaccines can cause autism. She wonders if Peter may be at risk as well.
How do you respond to her questions?
You inform Ms. Jones that the latest research has not shown a causal relationship between any of the routine childhood vaccines and autism. On the contrary, not vaccinating children places them at higher risk for developing complications secondary to diseases such as rubella, a known cause of autism.
It is most important to monitor the development of younger siblings of autistic children. The incidence of autism in monozygotic twins is 60%, while dizygotic twins and other siblings have a 5–6% risk of recurrence of autism (Bailey, Le Courteur, & Gottesman, 1995; Muhle et al., 2004). Although Peter shows no developmental delays at 18 months of age, he should be screened specifically for autism at 24 months of age. Some children will demonstrate a regression of developmental milestones between 18 and 24 months of age, so you will want to monitor Peter’s development carefully during the next year.
What additional information do you want to give James’s mother at this time?
Because caretakers of children with ASDs are frequently desperate to pursue any intervention that offers hope for improved outcome, it is imperative that providers educate them about unsubstantiated and ineffective therapies. These include sensory integration therapy, auditory integration training, behavioral optometry, craniosacral manipulation, dolphin-assisted therapy, music therapy, and facilitated communication. Likewise, there is as yet insufficient scientific evidence to support the use of biologic therapies such as restrictive diets, chelation therapy, gastrointestinal treatments, and dietary supplementation regimens (Barbaresi et al., 2006). Such ineffective therapeutic approaches offer false hope and may place unnecessary financial burdens on families.
Pharmacologic regimens may be indicated to alleviate disruptive behaviors such as aggression, self-injurious behaviors, sleep disturbance, and mood lability. Practitioners may consider a therapeutic trial of medication in the case of maladaptive behaviors not amenable to behavioral therapy. The U.S. Food and Drug Administration has approved risperidone (Myers et al., 2007; Shea et al., 2004) for the symptomatic treatment of aggressive and self-injurious behaviors in children with ASDs.
Rearing children with ASDs generates significant stress in families. The primary care provider can provide key support to the family through education and anticipatory guidance, and by serving as an advocate for the child. In some cases, referring family members for appropriate mental health services may be indicated. Longitudinal support can be accomplished by maintaining contact with the family through periodic health maintenance visits.
What is the long-term outlook for children diagnosed early with ASD?
A diagnosis of ASD is usually confirmed with clear behavioral indicators by 2 to 4 years of age. The earlier the diagnosis is made, the better the long-term outcome, assuming the child is placed in an early intervention program tailored to meet the needs of children with ASDs.
Key Points from the Case
1. All children should be screened for development at well child visits, with special attention given at the 9-month, 18-month, and 30-month visits (AAP, 2006).
2. Survey all children at every well child visit for early subtle signs of ASD, especially younger siblings of a child already diagnosed with an ASD.
3. Screen specifically for ASD at 18 and 24 months of age, consistently using at least one standardized screening tool.
4. If screening results are negative but concerns by parents or the clinician persist, schedule an early targeted visit to reassess the child.
5. Take action if the results of a screening test are positive or if the child demonstrates two or more risk factors. Rather than adopting a “wait-and-see” approach, refer the child for a comprehensive ASD evaluation, an audiologic evaluation, and an early intervention program in a timely manner.
6. Maintain a supportive, coordinating role as the primary care provider for the family with an autistic spectrum disordered child.
(See additional resources in Box 3-2.)
Box 3–2 Autism Resources for Providers
Choueiri, R., & Bridgemohan, C. (2005). To make the biggest difference, screen early for autistic spectrum disorders. Contemporary Pediatrics, 22, 54–67.
Johnson, C. P. (2008). Recognition of autism before age 2 years. Pediatrics in Review, 2, 86–96.
Mauk, J. E., Reber, M., & Batshaw, M. L. (2007). Autism and other pervasive developmental disorders. In M. L. Batshaw (Ed.), Children with disabilities (5th ed., Chapter 21). Baltimore: Brooks.
Zwaigenbaum, L., Bryson, S., Rogers, T., Roberts, W., Brian, J., Szatmari, P. (2005). Behavioral manifestations of autism in the first year of life. International Journal of Developmental Neuroscience, 23, 143–152. Available at: http://www.ncbi.nlm.nih.gov/pubmed/15749241
Autistic Spectrum Disorders: Best Practice Guidelines for Screening, Diagnosis and Assessment, California Department of Developmental Services: http://www.ddhealthinfo.org/documents/ASD_Best_Practice.pdf
Autistic Spectrum Disorders (Pervasive Developmental Disorders), National Institute of Mental Health: http://www.nimh.nih.gov/health/publications/autism/summary.shtml
First Signs, a Web site dedicated to the early identification and intervention of children with developmental delays and disorders. This site also contains an ASD video glossary that clinicians can access to view video recordings of diagnostic signs demonstrated by autistic children: http://www.firstsigns.org
Learn the signs. Act early, Centers for Disease Control and Prevention: http://www.cdc.gov/ncbddd/autism/actearly/
American Academy of Pediatrics Council on Children with Disabilities. (2006). Identifying infants and young children with developmental disorders in the medical home: An algorithm for developmental surveillance and screening. Pediatrics, 118, 405–420. Retrieved March 2, 2009, from http://pediatrics.aappublications.org/cgi/content/full/118/1/405
American Psychiatric Association. (2000). DSM-IV-TR diagnostic criteria for the pervasive developmental disorders. Retrieved November 23, 2008, from http://www.CDC.gov/ncbddd/autism/overview_diagnostic_criteria.htm
Autism and Developmental Disabilities Monitoring Network Surveillance Year 2000 Principal Investigators. (2007). Prevalence of autism spectrum disorders—autism and developmental disabilities monitoring network, six states, United States, 2000. Morbidity and Mortality Weekly Report, 56(SSO1), 1–11.
Bailey, A., Le Courteur A., & Gottesman, I. (1995). Autism as a strongly genetic disorder: Evidence from a British twin study. Psychological Medicine, 25, 63–77.
Baird, G., Charman, T., Baron-Cohen, S., Cox, A., Swettenham, J., Wheelwright, S., et al. (2000). A screening instrument for autism at 18 months of age: A 6-year follow-up study. Journal of the American Academy of Child and Adolescent Psychiatry, 39, 694–702.
Barbaresi, W., Katusic, S., & Voight, R. (2006). Autism: A review of the state of the science for pediatric primary health care clinicians. Archives of Pediatric and Adolescent Medicine, 160, 1167–1175.
Filipek, P., Accardo, P. J., Ashwal, S., Baranek, G. T., Cook, E. H., Dawson, G., et al. (2000). Practice parameter: Screening and diagnosis of autism. Neurology, 55, 468–479.
Muhle, R., Trentacoste, S., & Rapin, I. (2004). The genetics of autism. Pediatrics, 113, 472–486.
Myers, S. M., & Johnson, C. P. (2007). Management of children with autistic spectrum disorders. AAP Council on Children with Disabilities. Pediatrics, 120, 1162–1182.
Robins, D. I., Fein, D., Barton, M. I., & Green, J. A. (2001). The modified checklist for autism in toddlers: An initial study investigating the early detection of autism and pervasive developmental disorders. Journal of Autism and Developmental Disorders, 31(2), 149–151.
Schopler, E., Reichler, R. J., DeVellis, R. F., & Daly, K. (1980). Toward objective classification of childhood autism: Childhood Autism Rating Scale (CARS). Journal of Autism and Developmental Disorders, 10, 91–103.
Shea, S., Turgay, A., Carroll, A., Schultz, M., Orlik, H., Smith, I., et al, (2004). Risperidone in the treatment of disruptive behavioral symptoms in children with autistic and other pervasive developmental disorders. Pediatrics, 114(5), e634–e641.
Siegel, B. (2004a). Early screening for autism using the PDDST-II. AAP Society for Developmental and Behavioral Pediatrics News, 13, 4.
Siegel, B. (2004b). Pervasive Developmental Disorders Screening Test-II (PDDST-II): Early Childhood Screeners for Autistic Spectrum Disorders. San Antonio, TX: Harcourt Assessment.