Background: Tip-toe behavior (TTB) affects about 20%–30% of individuals with Autism Spectrum Disorder (ASD). A previous study found that TTB can manifest with varying degrees of increasing severity (i.e., TTB1 = TTB during running; TTB2 = TTB during walking and running; TTB3 = TTB during standing, walking and running). TTB persistence may lead to shortening of Achilles’ tendon, derived from Gastrocnemius muscle (GM) and the Soleus muscle (SM), which in turn influences motor function and quality of life. Traditionally, GM and SM length assessment is performed by measuring ankle dorsiflexion range of movement (ROM) with the knee extended (GM) and the knee 90° flexed (SM) using a manual goniometer placed on the individual’s skin. During clinical practice, this could become problematic in individuals with ASD and intellectual disability (ID) and/or sensory hypersensitivity. This limitation could be mitigated using a photography-based goniometry approach. In a previous pilot study, we found this approach feasible in children with ASD.

Objectives: This study aims 1) to apply a validated photography-based goniometry (DrGoniometer app) to measure GM and SM lengths in subjects with severe ASD and ID; 2) to evaluate the relationship between TTB severity and GM and SM length values.

Methods: We measured SM and GM length values in a sample of 36 individuals with ASD, diagnosed according to the DSM-5 criteria. ASD severity and ID were evaluated by the Childhood Autism Rating Scale - Second Edition (CARS-2) and the Raven's Coloured Progressive Matrices (RCPM), respectively. To determine the presence/absence of TTB and its severity, we applied a standardised qualitative assessment previously described. Photography-based goniometry measurements were conducted using the methodology described by Wang et al. (2019).

Results: Thirteen out of 36 subjects presented TTB. The mean age of the study sample was 8.42 years (SD 2.62), with no significant difference between NO-TTB and TTB individuals. The participants presented moderate to high ASD severity (mean CARS-2 score: 39.61, SD 6.46; range: 24.50-57) and a low IQ (mean RCPM score: 70.83, SD 19.91; range: 50-120), with no significant difference between NO-TTB and TTB individuals. Performing a comparison between GM and SM length values of NO-TTB and TTB individuals using Mann-Whitney tests, we found that TTB individuals resulted in significantly lower values in all four assessed muscles (GM_left: U=52.00, p<0.001; GM_right: U=51.50, p<0.001; SM_left: U=70.00, p=0.008; SM_right: U=62.00, p=0.003). Using the Spearman Rho test, we also found a significant inverse correlation between all four muscle lengths and the severity of TTB (GM_left: r=-0.593, p<0.001; GM_right: r=-0,567, p<0.001; SM_left: r=-0.490, p=0.002; SM_right: r=-0.506, p=0.002). Details about demographic and clinical characteristic of the study sample and GM and SM length values are summarized in Table 1.

Conclusions: Photography-based goniometry has been used successfully to quantify GM and SM muscle lengths in severe ASD individuals with ID, both with and without TTB. GM and SM length values are reduced in the TTB group. There is a moderate inverse relationship between TTB severity and GM and SM lengths. Further research is warranted to confirm the results.

Notes: 

1)School of Medicine and Surgery, University of Milano-Bicocca, Milano, Milano, Italy, (2)PhD Program in Neuroscience, University of Milano-Bicocca, Milano, Milano, Italy, (3)Autism Research Unit, Villa Santa Maria SCS, Tavernerio, Como, Italy