Scarf sign is to check the passive muscle tone in the neonatal period, the test is to put the arm such as the right arm around the neck to the left side, when normal the elbow joint does not exceed the midline of the chest; if the scarf sign is positive, that is, the elbow exceeds the midline of the chest refers to hypotonia; if at the same time in the presence of high risk factors before birth, at birth or after birth, such as prematurity, low birth weight babies, hypoxic ischemic encephalopathy, hypoglycemia, etc., along with symptoms such as weak cry when crying, weak sucking, breastfeeding difficulties, etc., suggest that it may be an early manifestation of brain injury, take the baby to the pediatric rehabilitation department in time to carry out the necessary training.