Even though 87% of autistic children have motor difficulties it is not one of the criteria for diagnosis (like repetitive movements) because motor impairments is also related to many other diagnoses.The difficulties in motor planning, gross motor skills, balance, coordination, and fine mine skills can range from mild to severe. Imitation of motor movements, like pointing or giving a thumbs up can also be difficult for many.
Decreased connectivity between regions of the brain can be a reason for impaired motor skills. A majority of children with autism who also have poor social skills tend to have decreased synchrony in the activity between their visual & motor regions. Other research shows decreased connectivity to the cerebellum, which helps to guide & correct movements. Still other evidence implicates weak connections between sensory & motor regions, important for motor planning.
Another very interesting fact is children with autism tend to rely more on their proprioception rather than vision — the more they rely on proprioception, the more severe their social deficits.Poor motor skills have a cascading effect for children with autism. Many cannot participate in sports and activities that are social. School work, including navigating the school, handwriting, etc will be difficult. And it will be difficult to follow along to conversations being had by multiple people.
The visual-motor integration skills that autistic people struggle with the most are also crucial to imitating and learning from others and participating in social interactions.
And the worst part? Only approx 32% of children with autism receive treatment for their motor impairments.