Hypotonia means decreased muscle tone.
Decreased muscle tone; Floppy infant
Hypotonia is often a sign of a worrisome problem. The condition can affect children or adults.
Infants with hypotonia seem floppy and feel like a "rag doll" when held. They rest with their elbows and knees loosely extended. Infants with normal tone tend to have flexed elbows and knees. They may have poor head control. The head may fall to the side, backward, or forward.
Infants with normal tone can be lifted with the adult's hands placed under the armpits. Hypotonic infants tend to slip between the hands as the infant's arms rise without resistance.
Muscle tone and movement involve the brain, spinal cord, nerves, and muscles. Hypotonia may be a sign of a problem anywhere along the pathway that controls muscle movement. Causes may include:
- Brain damage or encephalopathy, due to lack of oxygen before or right after birth, or problems with brain formation
- Disorders of the muscles, such as muscular dystrophy
- Disorders that affect the nerves that supply muscles
- Disorders that affect the ability of nerves to send messages to the muscles
- Rare genetic disorders, in which the body cannot properly turn food into energy
Genetic or chromosomal disorders, or defects that may cause brain and nerve damage include:
- Down syndrome
- Prader-Willi syndrome
- Tay-Sachs disease
- Trisomy 13
Other disorders that can lead to the condition include:
- Congenital hypothyroidism
- Congenital cerebellar ataxia
- Marfan syndrome
- Poisons or toxins
- Spinal cord injuries that occur around the time of birth
Take extra care when lifting and carrying a person with hypotonia to avoid causing an injury.
What to Expect at Your Office Visit
The physical exam will include a detailed examination of the nervous system and muscle function.
In most cases, a neurologist (specialist in brain and nerves) will help evaluate the problem. Geneticists may help diagnose certain disorders. If there are also other medical problems, a number of different specialists will help care for the child.
Which diagnostic tests are done depends on the suspected cause of the hypotonia. Most of the conditions associated with hypotonia also cause other symptoms that can help in the diagnosis.
Many of these disorders require ongoing care and support.
Burnette WB. The hypotonic (floppy) infant). In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Saunders Elsevier; 2012:chap 27.
Weinberg GA. Neuronal symptom complexes. In: Kliegman RM, Stanton BF, St. Geme JW III, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Saunders Elsevier; 2011:chap 23.
Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.