Evaluation of the floppy infant

The floppy infant represents a diagnostic challenge to paediatricians. Tone is the resistance to movement in a muscle and “floppy” is the term used for hypotonia, which is the feeling of reduced resistance of muscles to passive stretching. Hypotonia can arise from a wide range of disorders, from abnormalities of the central nervous system (CNS), any element of the peripheral neuromuscular system (the lower motor unit, LMN), or both. Establishing a diagnosis in the hypotonic infant is crucial for prognosis, management, treatment strategies and genetic counselling. The list of conditions to consider is increasingly complex and ever-growing, and a careful and thorough diagnostic approach is essential. This review will take you through the evaluation of the floppy infant, illustrated with two cases.