Description

• “Floppy infant” refers to the newborn/infant presenting at birth or early in life with hypotonia, a symptom of diminished tone of skeletal muscles associated with decreased resistance of muscles to passive stretching.
• Hypotonia can be caused by abnormalities of the CNS (central hypotonia), peripheral neuromuscular system (peripheral hypotonia), or combined abnormality involving both (combined hypotonia).
• Nonspecific transient hypotonia occurs in nonneurologic conditions and may suggest gastrointestinal (GI), cardiac, pulmonary, infectious, renal, or endocrine disease.

Epidemiology

No comprehensive prevalence known, owing to presence of hypotonia as a feature of many distinct disorders; overall, central hypotonia is more common than peripheral hypotonia.

Risk Factors

Etiology

Causes may be divided into two major categories:

• Central: hypotonia with decreased alertness, developmental delay, and lack of (or minimal) weakness; caused by upper motor neuron defect
• Peripheral: hypotonia with weakness, paucity of antigravity movements, decreased or absent deep tendon reflexes (DTRs), and visual alertness; caused by lower motor neuron defect (i.e., disorders of anterior horn cell, peripheral nerve, neuromuscular junction, or skeletal muscle)

Commonly Associated Conditions

• Respiratory problems (apnea/hypoventilation)
• Feeding/swallowing difficulties
• Hip dislocation/contractures/joint laxity
• Seizure disorder
• Cognitive/developmental delay
• Hypersomnolence