Dissociation of motor maturation

"(DMM) is a relatively unknown and underdiagnosed clinical syndrome. Identification of DMM is reliably made when the child demonstrates the classic ‘sitting on air’ position, which is recognized by a straight back, flexion, moderate abduction and outward rotation of the hips, extension of the knees and dorsiflexion or plantar flexion of the feet when held in vertical suspension (Figure 1). The position is elicited both when the child is at ease and when the child is angry. DMM is further characterized by normal cognitive, language, social-emotional and fine motor development, with an isolated delay in gross motor skills. Children with DMM generally achieve head and arm control within the expected timeframe but are delayed in achieving gross motor milestones, including sitting, standing and/or cruising, and walking."   (Bobbit et al 2016)

"DMM may be considered a specific outcome for children who are identified early on with congenital hypotonia with favourable outcome (formerly known as benign congenital hypotonia). It is also important to consider CP in the differential diagnosis of a child presenting with hypotonia and delayed motor development. Delayed, but ultimately normal motor outcomes, along with a normal neurological examination aside from hypotonia, will differentiate children with DMM from those who progress to receive a diagnosis of CP."  ( Bobbit 2016)   Read more https://academic.oup.com/pch/article/21/2/71/2647360

Sitting-on-air

Identification of DMM is reliably made when the child demonstrates the classic ‘sitting on air’ position, which is recognized by a straight back, flexion, moderate abduction and outward rotation of the hips, extension of the knees and dorsiflexion or plantar flexion of the feet when held in vertical suspension.  (Bobbit 2016)

Bibliography

Bobbitt, S. A., & Sonnenberg, L. K. (2016). Case 4: Isolated gross motor delay with 'sitting on air' position in an otherwise healthy 17-month-old. Paediatrics & child health, 21(2), 71–72. https://doi.org/10.1093/pch/21.2.71a

van der Heide, K., & Brand, P. L. (2004). 'Luchtzitten' bij zuigelingen: een teken van onschuldige achterstand in de grove motoriek ['Sitting on air' in infants: a sign of simple delay in the gross motor milestones]. Nederlands tijdschrift voor geneeskunde, 148(21), 1017–1020.