Quantitative and Qualitative Assessment of Diadochokinesia in Autism Spectrum Disorders

Background: Cerebellar abnormalities, with Purkinje neuron loss and impaired diadochokinesis as well as poor praxis performances have been reported in ASC.
Objectives: (1) to assess diadochokinesis, coordination skills and motor processing abilities in typically developing children (CG) and children diagnosed with ASC (High Functioning Autism and Asperger Syndrome), through the use of magneto-inertial devices (XSens MTx, XSens Motion Technologies®) applied to both wrists. (2) to evaluate the possible correlations between diagnosis, laterality, autistic traits and kinematic indexes.
Methods: 31 consecutive subjects (15 ASC; 16 CG) aged 5-14 years and matched for age, gender and IQ were compared. The Edinburgh Handedness Inventory assessed the lateral preference. The children version of the Autism-spectrum Quotient (AQ-Child), validated in Italian, was administered for quantifying the number of autistic traits, in a continuum of severity. The Total score (0-150) and the sub-scores in five different domains (Social Skills, Attention Switching, Attention to detail, Communication and Imagination) were rated. The kinematic analysis was conducted recording the prono-supination at the wrist joints at maximal and comfortable velocity respectively and after a trigger acoustic stimulus at five different frequencies from 1 to 5Hz. A real time visual feedback (in form of a 3-D cube on a computer screen, representing the orientation of one wrist) was given to the child in order to make the test more appealing. The following motor variables and indices were considered: (1) Prono-supination range (maximal angular excursion during the movement); (2) Prono-supination frequency (the inverse of the mean period of a complete prono-supination movements); (3) Main Prono-supination axis (the mean orientation of the axis around which the pronosupination movement takes place); (4) Inter-axes angle (the angle between the two main prono-supination axes); (5) Delay of one hand related to the other.
Results: Preliminary data analysis showed: (1) a statistical significant difference between ASC and CG in the AQ-Child total score and Social Skills, Attention Switching, Communication and Imagination sub-scores. (2) a significant positive correlation between right-handedness and the Main Prono-supination axis at 3 Hz. (3) a significant positive correlation between: (a) the AQ-Child (total score and Social Skills subscores) and the Prono-supination range at 2 Hz (b) the AQ-Child (total score and Social Skills, Communication, Imagination and Attention Switching subscores) and the Prono-supination frequency at 1 Hz. (4) a significant negative correlation between the AQ-Child (total, Imagination and Attention to detail scores) and the Prono-supination range at 5 Hz. (5) a significant negative correlation between right-handedness and the Inter-axes angle at 3 Hz, the Prono-supination range at 5 Hz and the Prono-supination frequency both right and left at 2-3 Hz.
Conclusions: Preliminary data analysis displayed a statistical significant difference between ASC and CG in the AQ-Child, with ASC group showing higher scores. The AQ scores also correlated with the kinematic indexes. In particular, at higher frequencies (5Hz) the AQ positively correlated with a worse performance. Further analyses are needed to better clarify the potentially peculiar patterns of motor impairment and dyspraxia in ASC.