Hypotonia is the medical term for low muscle tone that doctors usually diagnose in infants. The condition is less common in adults. People sometimes call it floppy muscle syndrome.

Usually, even when muscles relax, they have some contraction that provides some resistance to passive movement. However, hypotonia makes the muscles seem floppy because they have little muscle tension at rest.

Hypotonia can be a symptom of many different disorders and is not a sign of low intelligence. It is not necessarily due to muscle weakness and is often present from birth.

It is typically simpler for physicians to recognize hypotonia than to determine the cause.

This article examines the symptoms and causes of hypotonia. It also discusses how doctors diagnose and treat hypotonia and whether people can prevent the condition.

Share on Pinterest
Marlena Sloss/The Washington Post via Getty Images

Most people with hypotonia display symptoms before they are 6 months old. The most common symptoms are related to a lack of muscle tone.

Muscle tone allows someone to position their arms and legs, maintain their posture, and keep their organs working properly. However, low muscle tone affects all these activities.

Hypotonia is sometimes called “floppy baby syndrome.”

Other symptoms of hypotonia may include:

  • difficulty holding the head up
  • difficulties with sitting up
  • hanging limply in a person’s arms
  • an inability to place weight on the legs
  • difficulty sucking or swallowing
  • an inability to cry loudly
  • showing delays in reaching physical developmental milestones, such as crawling, walking, talking, and self-feeding

Hypotonia is often a symptom of another condition. The following are possible causes for hypotonia:

A complete and detailed medical history and a thorough physical examination are key steps in diagnosing hypotonia, particularly in infants.

A medical history will likely involve questions on:

  • the developmental history of the child and their parents
  • family history of hypotonia or genetic disorders
  • maternal exposure to toxins or infections during pregnancy
  • onset and progression of hypotonia

A physical examination for hypotonia will include a doctor:

  • looking for signs of congenital anomalies
  • testing to assess muscle tone
  • evaluating muscle strength and reflexes

Other tests and screenings doctors use to help look for possible causes of hypotonia include:

  • culturing urine, blood, and cerebrospinal fluid
  • blood tests
  • screening for metabolic disorders
  • MRIs or CT scans to observe the brain

If screenings and tests do not yield clear results, physicians may eventually diagnose children with benign congenital hypotonia, or BCH. This form of hypotonia does not usually progress, tends to improve with treatment, and may run in families.

Treatment for hypotonia generally focuses on providing a person and their family with the support they need to manage the condition.

Treatment can involve various healthcare professionals and practices, including:

Hypotonia is less common in adults than in infants and children. Hypotonia in adults usually starts in infancy rather than developing in adulthood. The symptoms and treatments are similar to those for children.

Just as children with hypotonia can have difficulty standing up, adults can have difficulty moving to an upright position after lying down. Adults may show increased flexibility in their joints and generally seem clumsy.

Occupational and physical therapy can help people manage their low muscle tone, while ongoing treatment for the condition’s cause can support general improvement.

The causes of hypotonia are generally different in children and adults. For example, adults may have hypotonia due to the following:

In a 2021 study, researchers suggested that hypotonia is a recognizable early marker for autism spectrum disorder (ASD). They described hypotonia as a “red flag” for ASD as most children diagnosed with autism also have other developmental-related diagnoses, such as poor muscle tone.

Identifying hypotonia as a marker for ASD can promote earlier evaluation, earlier diagnosis of autism, and earlier intervention. Researchers found that young males with hypotonia were diagnosed with ASD 1.5 years earlier, and young females 1 year earlier than people with ASD and no hypotonia.

It is challenging to prevent hypotonia as it is often the result of underlying, genetically-based preconditions.

People who want to have children can discuss options with a healthcare professional to deliver the baby in the safest way to prevent labor complications and birth injuries that may result in hypotonia.

During pregnancy, a person can protect the health of the child by:

  • following doctors’ recommendations for a healthy pregnancy
  • avoiding tobacco, drugs, and alcohol
  • eating a healthy diet
  • managing any health conditions that could affect the baby

The outlook for a person with hypotonia depends on the cause. For many people, hypotonia is a lifelong condition, but it may improve over time.

Infants with infantile botulism can often make a complete recovery. If sepsis causes hypotonia, treating the sepsis should reduce the symptoms. Some causes, such as Pompe disease, can be fatal.

With the assistance of various specialists, rehabilitation services, nutritional support, and home care services, a person’s outlook can alter, leading to better outcomes.

Hypotonia is the medical term for low muscle tone. Most people with hypotonia exhibit symptoms before 6 months old, although adults can also have it.

Many different factors can cause hypotonia, from genetic conditions to infections.

Hypotonia can be a lifelong condition. The outlook for a person with hypotonia depends on what causes poor muscle tone for that individual.

Treatment and physical and occupational therapy can help improve muscle tone for many people with hypotonia.