Natural History of Tiptoe Behavior in ASD

Background:

The literature confirms that 20-30% of individuals with autism walk on their tiptoes. In a previous study, we found that this behavior transpires not only during walking but also while standing and running, and described three mutually exclusive clinical functional classes. Systematic observations about the natural history of Tiptoe Behavior (TTB) in ASD children in the literature are scarce. Specifically, it is not known if TTB parallels the acquisition of standing, walking and running milestones or appears later on and if these milestones (using the criteria suggested by Dosman and Dedrick) are delayed compared to normally developing peers.

Objectives:

The aims of this retrospective study are: 1) to observe if TTB was exhibited simultaneously or subsequently to the acquisition of standing, walking and running milestones; 2) to describe, in those diagnosed subsequently, when TTB ASD subjects started to stand, walk and run compared to both normal population and non-TTB ASD subjects.

Methods:

Our study sample included 36 ASD subjects (34 males; mean age: 14.3 years) diagnosed with Autism according to the DSM V criteria, confirmed through ADOS 2 and under observation at our Institute. We asked all the subjects’ parents to answer a structured interview. We collected information about standing, walking and running milestones. We also asked if and when TTB was observed and when it eventually stopped. Another therapist confirmed the presence of TTB using a standardized method we described in a previous study.

Results:

We found that 18 subjects (50%) never showed TTB, 13 TTB subjects (36%) present TTB at least in one of three previous described situations, while 5 subjects (14%) had TTB in the past but it later stopped. The mean age of standing acquisition of the ASD sample resulted in line with the normative values, without significant differences between TTB and non-TTB subjects (table 1). The mean age of walking acquisition of the ASD sample resulted higher compared to the normative value (16.4 months (9-30 range) vs 12 months (9-18 range) respectively) without significant differences between TTB and non-TTB subjects. The mean age of running acquisition in the ASD sample resulted higher compared to the normative value (26.55 months ( 12-72 range) vs 15 months (13-20 range)) without significant differences between TTB and non-TTB subjects (absolute difference in favor of non-TTB). We observed that Tip-toe behavior in TTB subjects started significantly later than the acquisition of standing and walking milestone (table 2). Conversely, there was no significant difference between running acquisition and the start of TTB while running.

Conclusions:

TTB subjects exhibit this behavior significantly later to the acquisition of standing and walking milestones while there is no significant difference between running acquisition and the start of TTB while running. No significant difference in the age of acquisition of standing, walking and running milestones between TTB and non-TTB ASD subjects was found. The ASD sample showed a delay in walking and running acquisition compared to the normative values. This finding, if confirmed in other studies, could be included in the clinical abnormalities constellation of autism.