Bilateral Patterns of Repetitive Movements in 6- to 12-Month-Old Infants As a Red Flag for Autism Spectrum Disorders

Background: During the first year of life of an infant, repetitive movements represent a phase of typical motor development and they are considered a step towards voluntary purposeful movements. However, some types of repetitive movements and their higher frequency, from 12 months onwards, have been proved to distinguish infants with a Neurodevelopmental Disorders from infants with Typical Development (TD) . To distinguish between typical and atypical repetitive movements, the criteria that should be adopted are their frequency and the child’s age : in fact, a higher rate of these movements beyond their physiological temporal window might reduce the infant’s opportunity to develop more functional strategies of motor action. This is the case of Autism Spectrum Disorder (ASD), in which the persistence of repetitive and stereotyped movements during toddlerhood is considered, together with restricted interests and activities, one of the core symptoms.

Objectives: The purpose is to point out if a higher rate, duration and repertoire of repetitive movements could differentiate a) infants with ASD from infants with DD and TD aged between 6 and 12 months b) high-risk infants with ASD (HR-ASD), from high-risk infants without ASD (HR-nonASD), during the administration of the AOSI at 6 and 12 months of life.

Methods: We coded Repetitive Movements Episodes (RMEs), defined as a period of time characterized by a repetition of a movement for at least 2 times. We analyzed video-clips from retrospective homemade movies and from video-recordings of the AOSI administration, to compare the frequency and the duration of Repetitive Movement Episodes (RMEs) of a sample of 50 children equally distributed among the five groups (ASD, TD, DD, HR-ASD, HR-nonASD).

Results: Significantly higher total scores in RMEs with arms, hands, fingers and lower limbs were found to distinguish ASD infants from TD infants, with a satisfactory diagnostic efficiency (AUC>=80%). No significant difference was found between the distributions of unilateral RMEs between ASD and DD/TD. A similar difference was found between high-risk infants with ASD and without ASD. Results will be discussed in terms of the type of repetitive movements and of their implication for early diagnosis.

Conclusions: the results indicate that during the first year of life of life, an increased frequency of a particular repertoire of repetitive movements appears to be specific to ASD and could therefore be considered an early sign of the disorder.