floppy infant syndrome

abnormal posture in an infant suspended in the prone position, the limbs and head hanging limply. It may be due to any of numerous conditions, including disorders of the brain, spinal cord, peripheral nerves, neuromuscular junction, muscles, or ligaments, and only sometimes is characterized by true limb weakness; the most common causes are perinatal injury to the brain or spinal cord, spinal muscular atrophy, and genetic disorders.