Hypotonia, or severely decreased muscle tone, is seen primarily in
children. Low-toned muscles contract very slowly in response to a stimulus
and cannot maintain a contraction for as long as a normal muscle.
Hypotonia is a symptom that can be caused by many different conditions.
Hypotonia, also called floppy infant syndrome or infantile hypotonia, is a
condition of decreased muscle tone. The 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, genetic disorder, or 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 it can co-exist with muscle weakness.
Muscle tone indicates the ability of a muscle to respond to a stretch. For
example, if the flexed arm of a child with normal tone is quickly
straightened, the flexor muscle of the arm (biceps) will quickly contract
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. Muscles contract very
slowly in response to a stimulus and cannot maintain a contraction for as
long as a normal muscle. Because low-toned muscles do not fully contract
before they again relax, they remain loose and very stretchy, never
achieving their full potential of sustaining a muscle contraction over
Hypotonic infants, therefore, have a typical "floppy"
appearance. They rest with their elbows and knees loosely extended, while
infants with normal muscle tone tend to have flexed elbows and knees. Head
control is usually poor or absent in the floppy infant with the head
falling to the side, backward, or forward. Infants with normal tone can be
lifted by placing hands under their armpits, but hypotonic infants tend to
slip between the hands as their arms rise unresistingly upward. While most
children tend to flex their elbows and knees when resting, hypotonic
children hang their arms and legs limply by their sides. Infants with this
condition often lag behind in reaching the fine and gross motor
developmental milestones that enable infants to hold their heads up when
placed on the stomach, balance themselves, or get into a sitting position
and remain seated without falling over. Hypotonia is also characterized by
problems with mobility and posture, lethargy, weak ligaments and joints,
and poor reflexes. Since the muscles that support the bone joints are so
soft, there is a tendency for hip, jaw, and neck dislocations to occur.
Some hypotonic children also have trouble feeding and are unable to suck
or chew for long periods. Others may also have problems with speech or
exhibit shallow breathing. Hypotonia does not, however, affect intellect.
No demographic information as of 2004 was available for hypotonia, since
it is a symptom of an underlying disorder. However, a study conducted in
year 2000 by the University of Illinois provides some insights. The study
followed 243 infants with hypotonia for three to seven years. By the age
of three, about 30 percent had minimal problems and 46 percent had
significant impairments, while 24 percent of the infants were normal.
Hypotonic infants who matured into children with minimal disabilities were
highly likely to have poor motor coordination at age three (78%). About 25
percent had learning problems or
; 20 percent had borderline cognition or attention deficits; and 66
percent had two or more of these characteristics.
Causes and symptoms
Hypotonias are often of unknown origin. Scientists believe that they may
be caused by trauma; environmental factors; or by other genetic, muscle,
or central nervous system disorders. The National Institutes of Health
list the following common causes of hypotonia:
The following are common symptoms associated with hypotonia. Each child
may experience different
symptoms, depending on the underlying cause of the hypotonia:
Normally developing children tend to develop motor skills, posture
control, and movement skills by a given age. Motor skills are divided into
Gross motor skills
include the ability of an infant to lift its head while lying on the
stomach, to roll over from its back to its stomach. Normally, by a given
age, a child develops the gross motor skills required to get into a
sitting position and remain seated without falling over, crawl, walk, run,
Fine motor skills
include the ability to grasp, transfer an object from one hand to
another, point out an object, follow a toy or a person with the eyes, or
to feed oneself. Hypotonic children are slow to develop these skills, and
parents should contact their pediatrician if they notice such delays or if
their child appears to lack muscle control, especially if the child
previously seemed to have normal muscle control.
Hypotonia is normally discovered within the first few months of life.
Since it is associated with many different underlying disorders, the
doctor will accordingly seek to establish a
history as well as the child's medical history. A physical
examination will be performed, usually including a detailed nervous system
and muscle function examination. The latter may be performed with
instruments, such as lights and reflex hammers, and usually does not cause
to the child. Most of the disorders associated with hypotonia also cause
other symptoms that, when taken together, suggest a specific disorder and
cause for the hypotonia. Specific diagnostic tests used will vary
depending on the suspected cause of the hypotonia. Typical medical history
The following diagnostic tests may also be used:
When hypotonia is caused by an underlying condition, that condition is
treated first, followed by symptomatic and supportive therapy for the
hypotonia. Physical therapy can improve fine motor control and overall
body strength. Occupational and speech-language therapy can help
breathing, speech, and swallowing difficulties. Therapy for infants and
young children may also include sensory stimulation programs. Specific
treatment for hypotonia is determined by the child's physician
based on the following:
No specific treatment is required to treat mild congenital hypotonia, but
children with this problem may periodically need treatment for common
conditions associated with hypotonia, such as recurrent joint
dislocations. Treatment programs to help increase muscle strength and
sensory stimulation programs are developed once the cause of the
child's hypotonia is established. Such programs usually involve
physical therapy through an early intervention or school-based program
among other forms of therapy.
Hypotonic children are often treated by one or more of the following
In some hypotonic infants, sucking is weak and in some cases not present
at all. They do not act hungry or show interest in feeding. Special
techniques and procedures are then required to provide adequate
, such as special nipples, manipulation of mouth and jaw, and on rare
occasions, insertion of a gastrostomy tube.
The outcome in any particular case depends largely on the nature of the
underlying disease. Hypotonia can be life long, but in some cases, muscle
tone improves over time. Children with mild hypotonia may not experience
, although some children acquire gross motor skills (sitting, walking,
running, jumping) more slowly than most. Most hypotonic children
eventually improve with therapy and time. By age five, they may not be the
fastest child on the playground, but many will be there with their peers
and will be holding their own. Some children are more severely affected,
requiring walkers and wheelchairs and other adaptive and assistive
As of 2004 there was no prevention for hypotonia. However, measures of
prevention are increasingly possible in the early 2000s for several
Parents of an hypotonic child must follow the treating physician's
orders for treatment of the underlying cause. They must exercise special
care when lifting and carrying the hypotonic infant to avoid causing an
injury to the child. If lifted under the armpits, the hypotonic
infant's arms will raise with no resistance and easily slip between
A six-week-old baby girl is held horizontally by the trunk in a test
for hypotonia, sometimes called "floppy infant
syndrome." The girl is normal.
(Saturn Stills/Science Photo Library/Photo Researchers, Inc.)
Another source of concern that parents face is addressing the special
needs of their hypotonic child. The world of typical children can be a
difficult place for a hypotonic child, and it is tempting to isolate the
child. It is not easy to go to a playgroup of toddlers when a
child's latest milestone is getting from the floor into a sitting
position while the other children are running across the room. There are
resources for parents to help their child become as able and independent
as he or she can possibly be, and the family physician is a good resource
Bayley Scales of Infant Development
Amiel-Tison, Claudine, et al.
Neurological Development from Birth to Six Years: Guide for Examination
Baltimore, MD: Johns Hopkins University Press, 2001.
Preedy, Victor R., and Timothy J. Peters.
Skeletal Muscle: Pathology, Diagnosis, and Management of Disease
, 3rd ed. Edited by Kenneth J. Ryan. Albuquerque, NM: Health Press, 2002.
—A condition marked by impaired muscular coordination, most
frequently resulting from disorders in the brain or spinal cord.
—The muscle in the front of the upper arm.
—The surgical removal and microscopic examination of living
tissue for diagnostic purposes or to follow the course of a disease.
Most commonly the term refers to the collection and analysis of tissue
from a suspected tumor to establish malignancy.
Central nervous system
—Part of the nervous system consisting of the brain, cranial
nerves, and spinal cord. The brain is the center of higher processes,
such as thought and emotion and is responsible for the coordination and
control of bodily activities and the interpretation of information from
the senses. The cranial nerves and spinal cord link the brain to the
peripheral nervous system, that is the nerves present in the rest of
—A microscopic thread-like structure found within each cell of
the human body and consisting of a complex of proteins and DNA. Humans
have 46 chromosomes arranged into 23 pairs. Chromosomes contain the
genetic information necessary to direct the development and functioning
of all cells and systems in the body. They pass on hereditary traits
from parents to child (like eye color) and determine whether the child
will be male or female.
Computed tomography (CT)
—An imaging technique in which cross-sectional x rays of the body
are compiled to create a three-dimensional image of the body's
internal structures; also called computed axial tomography.
Fine motor skill
—The abilities required to control the smaller muscles of the
body for writing, playing an instrument, artistic expression and craft
work. The muscles required to perform fine motor skills are generally
found in the hands, feet and head.
—A muscle that serves to flex or bend a part of the body.
—A building block of inheritance, which contains the instructions
for the production of a particular protein, and is made up of a
molecular sequence found on a section of DNA. Each gene is found on a
precise location on a chromosome.
—A disease that is (partly or completely) the result of the
abnormal function or expression of a gene; a disease caused by the
inheritance and expression of a genetic mutation.
Gross motor skills
—The abilities required to control the large muscles of the body
for walking, running, sitting, crawling, and other activities. The
muscles required to perform gross motor skills are generally found in
the arms, legs, back, abdomen and torso.
—A physiological response of the body controlled by the immune
system that involves the production of antibodies to fight off specific
foreign substances or agents (antigens).
—The system of specialized organs, lymph nodes, and blood cells
throughout the body that work together to defend the body against
foreign invaders (bacteria, viruses, fungi, etc.).
Magnetic resonance imaging (MRI)
—An imaging technique that uses a large circular magnet and radio
waves to generate signals from atoms in the body. These signals are used
to construct detailed images of internal body structures and organs,
including the brain.
—The control of movement and posture.
—A nerve cell that specifically controls and stimulates voluntary
—Also termed tonus; the normal state of balanced tension in the
tissues of the body, especially the muscles.
—Reduction in the strength of one or more muscles.
—Any of the conducting cells of the nervous system that transmit
—Disorder that requires two copies of the predisposing gene one
from each parent for the child to have the disease.
—The elongated nerve bundles that lie in the spinal canal and
from which the spinal nerves emerge.
—Disorder or disease that causes the appearance of another
medical disorder or condition.
Child Development Institute (CDI).
3528 E. Ridgeway Road, Orange, California 92867. Web site:
Genetic and Rare Diseases Information Center.
PO Box 8126, Gaithersburg, MD 20898–8126. Web site:
March of Dimes Birth Defects Foundation.
PO Box 3006, Rockville, MD 20847. Web site:
Muscular Dystrophy Association.
3300 East Sunrise Drive, Tucson, AZ 85718–3208. Web site:
National Institute of Child Health and Human Development (NICHD).
31 Center Drive, Rm. 2A32, MSC 2425, Bethesda, MD 20892–2425. Web
National Institute of Neurological Disorders and Stroke (NINDS).
PO Box 5801, Bethesda, MD 20824. Web site:
National Organization for Rare Disorders (NORD).
PO Box 1968, 55 Kenosia Avenue, Danbury, CT 06813–1968. Web site:
Available online at
http://www.familyvillage.wisc.edu/lib_hypot.htm (accessed October
"What is Benign Congenital Hypotonia?"
Benign Congenital Hypotonia Site.
Available online at
October 18, 2004).