Neurophysiological correlates of motor problems

Motor difficulties occur in about half of people with ADHD.

Motor coordination is carried out by the cerebellum (the small brain). Motor problems are common in ADHD¹

Motor problems correlate with persistent primitive reflexes such as the asymmetric tonic neck reflex (ATNR) and the symmetric tonic neck reflex (STNR). More on this under Persistent tonic neck reflexes In the article Motor symptoms of ADHD in the chapter Symptoms

People with ADHD often show atrophy of the cerebellum, which correlates with problems of balance and gait control. These balance and movement disorders are associated with inhibitory deficits due to cerebellar abnormalities.²
Anti-Yo antibodies are immunoglobulin G (IgG) autoantibodies that react with a 62 kDa Purkinje cell cytoplasmic protein. They impair the function of the cerebellum (small brain).³ One study found anti-Yo antibodies in 77.5% of children with ADHD. The IL-6 and IL-10 plasma levels were also elevated in these children.⁴

An MRI study investigated the development of white matter organization in the corticospinal tract in adolescents. At ≈10 years of age, people with ADHD exhibited lower fiber density in the bilateral corticospinal tract than controls, regardless of their later motor status. These microstructural abnormalities persisted into adolescence in individuals with ADHD and motor problems, whereas they disappeared in individuals with ADHD without motor problems. Divergent maturational pathways of motor networks (i.e., the CST) may explain, at least in part, the motor problems of individuals with ADHD.⁵