Definition

Hypotonia means decreased muscle tone.

Alternative Names

Decreased muscle tone; Floppy infant

Considerations

Hypotonia is often a sign of a worrisome problem. The condition can affect children or adults.

Infants with this problem 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.

Causes

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, 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
• Infections

Genetic or chromosomal disorders, or defects that may cause brain and nerve damage include:

• Down syndrome
• Spinal muscular atrophy
• Prader-Willi syndrome
• Tay-Sachs disease
• Trisomy 13

Other disorders that can lead to the condition include:

• Achondroplasia
• Being born with hypothyroidism
• Poisons or toxins
• Spinal cord injuries that occur around the time of birth

Home Care

Take extra care when lifting and carrying a person with hypotonia to avoid causing an injury.

What to Expect at Your Office Visit

Your health care provider will do a physical exam including a detailed examination of the nervous system and muscle function.

In most cases, a neurologist (specialist in brain and nerve disorders) 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 make the diagnosis.

Many of these disorders require ongoing care and support. Physical therapy may be recommended to help children improve their development.

References

Barkoudah E. Encephalopathies In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 638.

Burnette WB. Hypotonic (floppy) infant. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds. Bradley and Daroff's Neurology in Clinical Practice. 8th ed. Philadelphia, PA: Elsevier; 2022:chap 30.

Manzur AY. Evaluation and investigation of neuromuscular disorders. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 647.

Marcdante KJ, Kliegman RM, Schuh AM. Weakness and hypotonia. In: Marcdante KJ, Kliegman RM, Schuh AM, eds. Nelson Essentials of Pediatrics. 9th ed. Elsevier; 2023:chap 182.