Idiopathic Toe Walking in Autism Spectrum Disorders and Associated Clinical Features

Background:

Previous research and clinical observations have indicated that children with autism spectrum disorders (ASD) often exhibit motor impairments and gait abnormalities.  Among these, idiopathic toe-walking (ITW) appears to occur at a particularly high rate.  However, few studies have specifically examined the incidence, prevalence, or associated features of ITW in this population. Idiopathic toe-walking is generally defined as toe-walking that persists for longer than 3 months after independent walking begins—with all other physiological and anatomical causes being excluded.

Objectives:  

The primary purpose of this study was to examine the prevalence of ITW among children with varying ASD subtypes. Our second objective was to determine whether toe-walking is correlated with differences in specific clinical features and measures of severity among children with ASD. 

Methods:  

Retrospective data were examined from 829 children and adolescents with ASD seen in an outpatient autism specialty clinic between 1994 and 2010.  Participants ranged in age from 3 to 20 (average age of 8.0 years).  Regarding diagnosis, 57.5% met diagnostic criteria for Autistic Disorder, 27.6% for PDD NOS, and 14.8% for Asperger's Syndrome.  Toe-walking was determined from a parent-report history questionnaire completed at intake. Possible non-idiopathic causes of toe-walking were excluded by excluding children with abnormal MRIs or extreme prematurity.  For a subset of the population, additional measures of associated clinical features were examined.   Measures included Full Scale IQ (n=257), Social Communication Questionnaire (SCQ) (n=150), Vineland Adaptive Behavior Scale – 2^nd Edition Communication Subscale (n=228), Child Behavior Checklist Externalizing (CBCL) Symptoms subscale (n=209), and Short Sensory Profile (SSP) (n=189).

Results:  

Results indicated that prevalence of idiopathic toe-walking was high (40.5%).  Autistic Disorder had the highest overall prevalence (45.1%), with a lower prevalence among those with Asperger's Syndrome (30.1%).  Differences between children with and without a history of ITW were examined using ANCOVA analyses controlling for age.  Children with a history of ITW had significantly higher scores on the SCQ (p < .01) and CBCL Externalizing Scale (p < .05) and significantly lower IQ (p < .01) and SSP scores (p < .01).  No significant differences were found on the Vineland Communication Scale.  Logistic regression analysis was used to examine subscale scores of the SSP, and results indicated that the “under responsiveness/sensation seeking” category was a statistically significant predictor of history of ITW.

Conclusions:  

The results of the current study show that a history of idiopathic toe-walking is very prevalent in children with ASD. ITW is associated with greater autism severity, and those with a history of ITW had lower cognitive functioning, greater difficulty with behavioral regulation, and more impaired sensory processing. These findings indicate that ITW may be a biomarker of poorer outcomes for children with ASD. Future studies using prospective, longitudinal designs and standardized measures of motor impairment would be helpful to more fully investigate these issues.