What assessment finding indicates primary CNS dysfunction in an infant?

Poor muscle tone is a significant indicator of primary central nervous system (CNS) dysfunction in an infant. Muscle tone refers to the tension in the muscles at rest and how well the muscles are able to respond to commands or stimuli. In healthy infants, muscle tone typically presents with a certain degree of resistance to passive movement, and they are able to exhibit appropriate postures.

When an infant demonstrates poor muscle tone, known as hypotonia, it can indicate underlying neurological issues such as damage to the brain, developmental delays, or metabolic disorders that affect motor control. This condition means that the infant may appear floppy, have difficulty holding their head up, or struggle with movements that require strength or coordination.

In contrast, nasal flaring could suggest respiratory distress rather than a CNS issue, easily distracted behavior is more indicative of engagement and attention-related issues, and pale extremities might be associated with circulatory problems rather than direct CNS dysfunction. Therefore, the presence of poor muscle tone is a clear and critical finding that points toward potential neurological concerns in infants.