Stereotyped Behaviors and Restricted Interests In Toddlers with ASD: Prevalence and Diagnostic Significance

Background:  The early diagnosis of autism spectrum disorder (ASD) has become an important clinical and public health goal.  Autism-specific screening instruments designed for use with toddlers rely heavily on documentation of social communicative impairment rather than the presence of atypical interests and behaviors for characterizing young children as at risk for ASD.  The literature has suggested that mannerisms, unusual sensory interests, and restricted interests/repetitive behaviors become more evident in the clinical profile of children with ASD closer to 3 years of age.  That said, what is the diagnostic significance when these atypical behaviors and interests are present in toddlers with social communicative impairment? 

Objectives: To examine the prevalence and types of mannerisms (MAN), unusual sensory interests (USI), and restricted interests/repetitive behaviors (RRB) present in young children who received a diagnosis of ASD by age 24 months (mo) and to assess the relationship between early manifestation of MAN/USI/RRB and stability of ASD diagnosis.  

Methods: Retrospective chart review of 74 children presenting by age 24 mo to a University Affiliated early intervention program from 2003 to 2009 who received an ASD diagnosis based on multidisciplinary evaluation and who had follow-up at least 1 year later. Data from initial evaluation included: age, demographics, cognition, DSM-IV criteria, Childhood Autism Rating Scale (CARS) and, in some, the Autism Diagnostic Observation Schedule (ADOS).  Characterization of MAN/USI/RRB was based on observations across the multidisciplinary evaluation sessions. ASD diagnosis at follow-up was based on CARS, DSM IV, ADOS, and educational classification.  Data of those who retained ASD diagnosis and those who did not were compared. Statistical analysis included chi-square, t-test and nonparametric testing.

Results: Mean age at presentation was 19.9 mo; 68% male; 64% cognitive standard score > 70.  At follow-up, mean age was 54.1 mo.  87% of the sample continued to meet criteria for ASD at follow-up.  At initial presentation, 87.8% of the sample displayed atypical behaviors.

Frequency of Atypical Behaviors
Motor Mannerisms (MAN): 55/74 e.g., Hand flapping (24%), Toe walking (19%), Spinning around (26%)	74%	Unusual Sensory Interests (USI): 45/74 e.g., Visual: Eye level play, Squinting, etc. (27%); Other: Licking, Smelling, etc. (34%)	61%	Restricted Interests/ Repetitive Behaviors (RRB): 39/74 e.g., Spinning objects/ wheels (24%), Lining up toys (4%)	53%

The children who continued to meet criteria for ASD at follow-up were more likely to have displayed MAN/USI/RRB at presentation than those who did not (92% vs. 60%, p=0.004). They were especially likely to display motor mannerisms (78% vs. 20%, p<0.001) and to exhibit 2 or more types of MAN/USI/RRB  (95% vs. 73%, p=0.006).  Those who presented with any MAN/USI/RRB had a significantly higher total CARS score at follow-up (32.8±6.8 vs. 25.7±6.1. p=0.03). 

Conclusions:  Atypical behaviors were commonly seen in children presenting early with social communicative deficits given an ASD diagnosis.  The vast majority of this cohort retained ASD diagnosis at follow-up.  The presence of atypical interests and behaviors was predictive of stability of the early diagnosis.