Evaluation and Differential Diagnosis of the Hypotonic Infant

Abstract

1. Victor Dubowitz 1. Professor of Paediatrics, Department of Paediatrics and Neonatal Medicine, Royal Post-graduate Medical School, Hammersmith Hospital, Du Cane Road, London W12 OHS, England Floppiness or hypotonia in an infant is a common clinical problem and may be associated with a wide range of apparently unrelated disorders. It may be the presenting feature of a neuromuscular disorder; it may occur in the newborn period as a result of a perinatal insult to the central nervous system or may manifest later in infants with mental retardation or cerebral palsy; it may be a manifestation of a connective tissue disorder; it may be associated with various metabolic disorders in infancy; it may be an incidental and nonspecific feature of an acutely ill child and it is completely physiologic in the premature infant. Irrespective of the cause, the floppy infant is likely to present a somewhat similar clinical picture, which one usually recognises on the basis of three clinical signs: (1) bizarre or unusual posture, (2) diminished resistance of the joints to passive movement, and (3) increased range of joint movement. In the newborn period, the infant usually presents with the above features, together with a paucity of active movement; the older infant usually presents with delay in motor milestones. In the evaluation and diagnosis of the hypotonic infant, careful attention should be paid to the history and clinical examination as one is likely to get more help from these in arriving at a diagnosis than from many of the more sophisticated and specialized investigations.