Hypotonic: Definition, Symptoms, Causes, Diagnosis and Treatment

The word comes from the Greek “hypo,” which means “low,” and from “tones,” which means a stretch.

The term hypotonic can mean several things in biology. Its many definitions apply to both human biology and biochemistry.

Hypotonia, when referring to humans or animals, also means that a muscle has less tone, or shape, compared to an average comparison model or when compared to another power in the same individual’s body.

Hypotonic is a medical word for low muscle tone. It occurs in babies and is also called a lazy baby syndrome.

The hypotony in the baby makes him feel lazy when held, like a cloth doll. This condition can be diagnosed in the first minutes of a baby’s life.

Doctors perform muscle tone checks on newborns immediately after birth.

A hypotonic baby with poor muscle tone shows difficulty with the brain’s functioning, spinal cord, nerves, or muscles.


Physical therapy and other treatments can help your baby develop stronger muscles and better motor coordination.


Good muscle tone allows babies to flex and shake their limbs. A newborn with hypotonia will not be able to develop these strong movements of the arms and legs.

Common symptoms of a hypotonic baby include:

  • Impossibility to control the head: It is impossible to control the neck muscles. Therefore the head will move forward, backward, or sideways without control.
  • The arms and legs of the baby hang straight: generally, the arms and the legs of the babies when they hang remain flexed; slight flexion is observed in the elbows, hips, and knees. However, babies with hypotonia do not have this flexion.

Often, this condition can cause problems with sucking and swallowing. In addition, highly flexible joints are observed, as if presenting a double joint.

Causes of hypotonia

The hypotonic baby syndrome can occur without an apparent cause, called benign congenital hypotonia.

But often, it is related to some underlying disease. Possible causes are:

  • Brain damage is caused before or after childbirth.
  • Problems in the formation of the brain in the womb.
  • Nervous system disorders.
  • Down syndrome or trisomy 21.
  • There are problems in functioning specific genes located on chromosome 15 or Prader-Willi syndrome.
  • Tay-Sachs disease or a genetic mutation in the HEXA gene on chromosome 15.
  • Achondroplasia (bone dysplasia causing dwarfism).
  • Some spinal cord injuries.
  • Serious infections.

A premature baby is likely to have poor muscle tone because their body has not had enough time for proper development.

Over time and with proper treatment, you can overcome this condition.


Medical and genetic history is carried out, accompanied by a physical examination.

In this exam, the following are verified:

  • Motor skills.
  • Sensory abilities.
  • The equilibrium.
  • Coordination.
  • The state of mind.
  • The reflections.

Various tests can be performed, such as:

  • An MRI or CT scan of the brain.
  • Laboratory exams.
  • Electromyography to evaluate the function of the nerves and muscles.
  • An EEG to assess electrical activity in the brain.
  • A lumbar puncture.
  • A biopsy in the forces.
  • Some genetic tests.
  • The baby’s conditions will be evaluated before birth or during delivery.

Treatment of hypotonia

Once the cause of the baby’s hypotonia has been diagnosed, treatment aims to combat this condition.

When the problem that causes hypotonia is not treated, as in the case of a hereditary condition, for example, Down syndrome, that condition will be present for life.

The use of therapies for strengthening and improving muscle coordination is recommended. Such as:

  • The programs to stimulate the senses: to improve the problems that babies have with vision, hearing, touch, smell, and taste.
  • Occupational therapies: these therapies contribute to the development of fine motor skills, which are essential for the performance of daily tasks.
  • Physical therapies: helps control the baby’s movements, improving strength and muscle tone over time.
  • Speech therapies: help control breathing, language, and swallowing deficiencies.