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, while infants with normal tone tend to have flexed elbows and knees. They may have poor or no head control. The head may fall to the side, backward, or forward.

Infants with normal tone can be lifted with the parent'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
  • Problems with brain formation
• Disorders of the muscles, such as muscular dystrophy
• Disorders that affect the nerves that supply muscles (called motor neuron disorders)
• Disorders that affect the ability of nerves to send messages to the muscles:
  • Infant botulism
  • Myasthenia gravis
• Inborn errors of metabolism (rare genetic disorders in which the body cannot properly turn food into energy)
• Infections
• Other genetic or chromosomal disorders or defects that cause brain and nerve damage, such as:
  • Down syndrome
  • Prader-Willi syndrome
  • Tay-Sachs disease
  • Trisomy 13
• Other miscellaneous disorders:
  • Achondroplasia
  • Congenital hypothyroidism
  • Congenital cerebellar ataxia
  • Marfan syndrome
  • Poisons or toxins
  • Spinal cord injuries that occur around birth

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

The physical examination will probably include a detailed examination of the nervous system and muscle function.

A neurologist (specialist in brain and nerves) will usually 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.

Fenichel GM. The hypotonic (floppy) infant). In: Bradley WG, Daroff RB, Fenichel G, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 29.

Review Date: 12/01/2011

John Goldenring, MD, MPH, JD, Pediatrician with the Sharp Rees-Stealy Medical Group, San Diego, CA. Review provided by Verimed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.