Hypotonia

Alternative names:

floppy; decreased muscle tone, hypotonic infant

Definition:

Decreased muscle tone, generally in an infant. There is a rag doll-like feeling or sense of floppiness upon holding the infant.

Considerations:

Hypotonia is often a sign of abnormality in the case of a newborn or older infant, and may suggest the presence of central nervous system dysfunction, genetic disorders, or muscle disorders.

Hypotonic infants rest with their elbows and knees loosely extended, while infants with normal tone tend to have flexed elbows and knees. Head control may be poor or absent in the floppy infant with the head falling to the side, backward or forward. .

Infants with normal tone can be lifted with the parent's hands placed under the armpits, while hypotonic infants tend to slip between the hands as the infant's arms rise upward.

Common causes:

• Down syndrome
• myasthenia gravis
• Prader-Willi syndrome
• Kernicterus
• cerebellar ataxia, congenital
• Werdnig- Hoffman
• myotonic dystrophy
• infant botulism
• familial dysautonomia (Riley-Day syndrome)
• Marfan's syndrome
• muscular dystrophy
• achondroplasia
• trisomy 13
• sepsis
• Aicardi syndrome
• Canavan disease
• congenital hypothyroidism
• hypervitaminosis D
• Krabbe disease
• Menke's syndrome
• metachromatic leukodystrophy
• methylmalonic acidemia
• rickets
• spinal muscular atrophy type 1
• Tay-Sachs disease
• vaccine reaction

Note: There may be other causes of hypotonia. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as quality, time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for hypotonia, occurring alone or in combination with other problems.

Update Date: 02/09/00
Updated by: J. Gordon Lambert, MD, Associate Medical Director, Utah Health Informatics and adam.com editorial