Can attention deficit hyperactivity disorder and fetal alcohol spectrum disorder be differentiated by motor and balance deficits?

There is an ongoing debate regarding the diagnostic overlap between Attention Deficit Hyperactivity Disorder (ADHD) and Fetal Alcohol Spectrum Disorder (FASD). Differential diagnosis is important because of treatment implications. Children aged 7-10years (47 ADHD, 30 FASD, 39 controls) participated. The Movement Assessment Battery for Children (M-ABC) and the Clinical Observations of Motor and Postural Skills (COMPS) were used. Force plate and electromyography data were collected during static balance and balance perturbation. On the M-ABC both children with ADHD and FASD had more motor problems than controls. The ADHD-Combined and the ADHD-Predominantly Inattentive subgroups were similarly affected in their fine motor skills. On the COMPS, the majority of children in both groups performed in the normal range, but for those children clinically affected, it was the children with ADHD who were more likely to be severely impaired. The children with ADHD were characterized by early onset latencies of the tibialis anterior muscles and increased amplitudes of the gastrocnemius muscles. Difficulty scaling muscle force reflecting medial cerebellar involvement may be the key problem in ADHD. Cerebellar involvement in the postural instability in FASD awaits further study.