2.4. Phenotypic assessment of physiologic immature motor patterns

Five investigators (three pediatric neurologists and two MD PhD students in pediatric movement disorders) independently assessed the motor patterns for the neurological phenotypic appearance. The average duration per phenotypic assessment was 10 min. For this task, the assessors applied the definitions of movement disorder features as the gold standard (see Supporting Information Appendix S2). For the assessment form, see Supporting Information Appendix S3.

In each child, we calculated the percentage of observers who phenotypically recognized the same movement disorder features (i.e., the % movement disorder recognition). If the same movement disorder feature was indicated by the majority of observers (≥3/5 observers), we considered the indicated movement disorder feature as “reproducible.” Subsequently, we analyzed the occurrence of reproducible movement disorder features per age subgroup (0, 3, 6, 9, 12, 18, 24, and 36 months of age, n = 4/age subgroup). When the majority of children per age subgroup (≥2/4) revealed the same reproducible movement disorder features, the indicated features were processed as “main” movement disorder features for that particular age subgroup. This implies that main movement disorder features are indicated by the majority of the observers in the majority of children per age subgroup.

We determined inter‐observer agreement for the obtained main movement disorder features (between five assessors). Furthermore, we associated the percentage of main movement disorder features with the age of the subgroups and also with the identified developmental motor patterns, involving GM characteristics using Gestalt Perception (by AFB, expert and co‐founder of the GM trust) and the identification of primitive reflexes (startles and asymmetric tonic neck reflex [ATNR]) and voluntary motor patterns (such as sitting, standing, walking, reaching, and voluntary grasping).