Hypotonia: Muscle Tone, Causes, Symptoms, Diagnosis and Treatment

Also called flaccid child syndrome, it is a condition of decreased muscle tone that can be caused by many different conditions.

Low-tone muscles contract very slowly in response to a stimulus and can not maintain a contraction for as long as a normal muscle.

Hypotonia, or severely decreased muscle tone, is observed mainly in children.

Muscular tone

Low muscle tone can be caused by a variety of conditions and is often indicative of the presence of an underlying central nervous system disorder , a genetic disorder or a muscle disorder.

Muscle tone is the amount of tension or resistance to movement in a muscle.

It is not the same as muscle weakness, which is a reduction in the strength of a muscle, but can coexist with muscle weakness.

Muscle tone indicates a muscle’s ability to respond to a stretch.

For example, if the flexed arm of a normal-toned child straightens quickly, the flexor muscle of the arm (biceps) will contract rapidly in response.

Once the stimulus is removed, the muscle then relaxes and returns to its normal resting state.

A child with low muscle tone has muscles that are slow to start a muscle contraction.

The muscles contract very slowly in response to a stimulus and can not maintain a contraction as long as a normal muscle.

Because the low tone muscles do not contract completely before they relax again, they remain loose and very elastic, without reaching their maximum potential to sustain a muscle contraction over time.

They rest with their elbows and knees slightly extended, while babies with normal muscle tone tend to have their elbows and knees flexed.

The control of the head is usually poor or absent in the baby with the head dropped to one side, backward or forward.

Normal-toned babies can get up by placing their hands under the armpits, but hypotonic babies tend to slip between their hands as their arms rise without resistance upward.

While most children tend to flex their elbows and knees when they rest, hypotonic children hang their arms and legs without strength at their sides.

Babies with this condition often fall behind in reaching the fine, thick motor development milestones that allow babies to hold their heads when they are placed in the stomach, maintain balance, or sit and remain seated without falling.

Hypotonia is also characterized by problems of mobility and posture, lethargy, weak ligaments and joints and poor reflexes.

Since the muscles that support the joints of the bone are so soft, there is a tendency for hip, jaw, and neck dislocations to occur.

Some hypotonic children also have trouble feeding and can not suckle or suckle for long periods of time.

Others may also have problems with speech or show shallow breathing. Hypotonia, however, does not affect the intellect.


Hypotheses are often of unknown origin.

Scientists believe that they can be caused by trauma; environmental factors; or for other genetic, muscular or central nervous system disorders. The National Institutes of Health lists the following common causes of hypotonia:

Down Syndrome:  A chromosomal abnormality, usually due to an additional copy of the twenty-first chromosome.

Myasthenia gravis:  A neuromuscular disorder characterized by the variable weakness of voluntary muscles, which often improves with rest and worsens with activity. The condition is caused by an abnormal immune response.

Prader-Willi syndrome:  A congenital disease characterized by obesity, severe hypotonia and decreased mental capacity

Kernicterus:  Also called Rh incompatibility, a condition that develops when there is a difference in the Rh blood type between that of the mother (Rh negative) and that of the fetus (Rh positive).

Cerebellar ataxia:  A movement disorder that with its sudden onset, often after an infectious viral disease, causes hypotonia.

Infant  botulism : A type of botulism, in which Clostridium Botulinum bacteria grows inside a baby’s digestive tract, producing a toxin that can be life-threatening.

Family dysautonomia:  Also called Riley-Day syndrome , a hereditary disorder that affects the function of nerves throughout the body.

Marfan syndrome:  A hereditary disorder of the connective tissue (tissue that strengthens the structures of the body), which affects the skeletal system, the cardiovascular system, the eyes and the skin.

Muscular dystrophy:  A group of disorders characterized by progressive muscle weakness and loss of muscle tissue.

Achondroplasia:  A bone growth disorder that causes the most common type of dwarfism.

Trisomy 13:  A syndrome associated with the presence of a third chromosome number 13.

Sepsis:  A serious life-threatening disease caused by an overwhelming infection of the bloodstream by toxin-producing bacteria.

Aicardi syndrome:  A rare genetic disorder characterized by infantile spasms (shaking), absence of the corpus callosum (the connection between the two hemispheres of the brain), mental retardation, and lesions of the retina of the eye or optic nerve.

Canavan disease:  A hereditary metabolic disorder characterized by the degeneration of white matter.

Hypervitaminosis D:  A condition that appears several months after excessive doses of vitamin D are given.

Krabbe disease:  A hereditary disorder characterized by a deficiency of the enzyme galactosylcereamidase, resulting in the destruction of myelin , the fatty material that surrounds and isolates many of the nerves.

Metachromatic leukodystrophy:  A hereditary disease characterized by the absence of the enzyme arylsulfatase A, which causes a material called cerebroside sulfate to accumulate in cells, which is toxic to cells, especially to cells of the nervous system.

Methylmalonic:  A hereditary metabolic disorder, usually diagnosed in childhood, that causes the accumulation of methylmalonic acid in the body and can cause serious metabolic disorders.

Spinal muscular atrophy type 1 (Werdnig-Hoffman):  A group of inherited diseases that cause progressive muscle degeneration and weakness, and ultimately lead to death.

Tay-Sachs disease:  A genetic disorder that is predominantly found in Jewish families and results in premature death.

Reaction to the vaccine:  Any injury or condition that occurs as a result of a vaccination.


Each child may experience different symptoms, depending on the underlying cause of the hypotonia:

  • Decreased muscle tone; the muscles feel soft.
  • Ability to extend the limb beyond its normal limit.
  • Inability to acquire motor skills in milestones of development (such as holding the head without parental support, turning around, sitting without support, walking).
  • Feeding problems (inability to suck or chew for prolonged periods).
  • Shallow breathing, the mouth hangs with the tongue sticking out.

When to call the doctor

Children with normal development tend to develop motor skills, posture control and movement skills at a certain age.

Motor skills are divided into two categories. Thick motor skills include a child’s ability to lift his head while lying on his stomach, to roll over from his back to his stomach.

Normally, at a certain age, a child develops the gross motor skills necessary to sit and sit without falling, crawling, walking, running and jumping.

Fine motor skills include the ability to grab, transfer an object from one hand to another, point to an object, follow a toy or person with the eyes, or feed.

Hypotonic children are slow to develop these skills, and parents should contact their pediatrician if they notice such delays or if their child seems to lack muscle control, especially if the child previously appeared to have normal muscle control.


Hypotonia is usually discovered within the first months of life.

Since it is associated with many different underlying disorders, the doctor will seek to establish a family history as well as the child’s medical history.

A physical examination will be performed, which usually includes a detailed examination of the nervous system and muscle function.

The latter can be performed with instruments, such as lights and reflex hammers, and usually does not cause any pain to the child.

Most disorders associated with hypotonia also cause other symptoms that, when taken together, suggest a specific disorder and the cause of the hypotonia.

The specific diagnostic tests used will vary according to the suspected cause of the hypotonia.

The following diagnostic tests can also be used:

Test (CK) : High level of CK in blood that indicates that the muscles are damaged or degenerated.

Computed tomography (CT) scan: An imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images. CT scans help doctors evaluate bone and muscle structures.

Magnetic resonance imaging (MRI):  A diagnostic procedure that uses a combination of large magnets, radio frequencies, and a computer to produce detailed images of organs and structures within the body.

Electroencephalogram (EEG): A test that measures electrical activity in the brain. An EEG measures brain waves through small button electrodes that are placed on the child’s scalp.

Spinal tap : Also called lumbar puncture, measures the amount of pressure in the spinal canal and / or removes a small amount of cerebrospinal fluid for testing. Cerebrospinal fluid bathes the brain and spinal cord.

Karyotype: Test that performs a chromosomal analysis from a blood test to determine if the hypotonia is the result of a genetic disorder.

Muscle biopsy: Sample of muscle tissue removed and examined under a microscope. Hypotonia can be evaluated because muscle fibers have a smaller diameter than normal muscle.


When hypotonia is caused by an underlying condition, that condition is treated first, followed by symptomatic therapy and support for hypotonia.

Physical therapy can improve fine motor control and general body strength.

Occupational and speech and language therapy can help you breathe, talk and swallow. Therapy for infants and young children can also include sensory stimulation programs.

The specific treatment for hypotonia is determined by the child’s doctor as follows:

  • The age of the child, his general state of health and his medical history.
  • The extent of the condition.
  • The underlying cause of the condition.
  • The child’s tolerance for medications, procedures or therapies.
  • Expectations for the course of the condition.

No specific treatment is required to treat mild congenital hypotonia, but children with this problem may need treatment periodically for common conditions associated with hypotonia, such as recurrent joint dislocations.

Treatment programs to help increase muscle strength and sensory stimulation programs develop once the cause of the child’s hypotonia is established.

Such programs usually involve physical therapy through early intervention or a school program among other forms of therapy.

Hypotonic children are often treated by one or more of the following specialists:

Pediatrician of development:  A pediatrician with specialized training in children and intellectual development, as well as health and physical growth.

He or she can perform a developmental assessment that will determine any delay the child has and to what extent the delay is present.

Neurologist:  A doctor who has been trained in the diagnosis and treatment of disorders of the nervous system, including diseases of the brain, spinal cord, nerves and muscles.

Neurologists perform neurological exams of the nerves of the head and neck; strength and muscular movement; balance, ambulation and reflexes; and sensation, memory, speech, language and other cognitive abilities.

Geneticist:  Specialist in genetic disorders. He or she begins with the detailed history of the family history, examines the child’s characteristics, and orders blood tests to look at the 46 chromosomes and possibly specific genes on those chromosomes.

Occupational Therapist (OT):  A professional who has specialized training to help develop mental or physical skills that help achieve activities of daily living, with careful attention to improve fine motor skills.

In a developmental assessment, the occupational therapist evaluates the child’s fine motor skills, coordination, and age-appropriate self-help skills (eating with utensils, dressing, etc.).

Physiotherapist (FT):  A professional trained in evaluating and providing therapy to treat developmental delays using methods such as exercise, heat, light and massage.

In a developmental assessment, the physiotherapist assesses the capacity and quality of the child’s use of the legs, arms and whole body by observing the deployment of specific motor skills and observing the child in the game.

Speech / language pathologist (TDL)):  A professional trained in the evaluation and treatment of communication problems.

Some SLPs are also trained to work with oral / motor problems, such as swallowing and other feeding difficulties resulting from hypotonia.

Nutritional concerns In some hypotonic children, the suction is weak and in some cases is not present at all. They do not feel like eating.

Special techniques and procedures are required to provide adequate nutrition, such as special nipples, manipulation of the mouth and jaw, and in rare cases, the insertion of a gastrostomy tube.