Hypotonia causes the muscles to lose tone and structure; this can affect movement and change the physical appearance of the affected limb (affected muscles usually look very floppy and limp). Hypotonia is usually a symptom of another health condition. Hypotonia may be congenital (meaning people are born with condition) or acquired (meaning that people develop it after birth).
What causes hypotonia?
Hypotonia may be caused by a number of different health conditions that affect the muscles, brain or the nervous system; these include:
- Neuromuscular conditions: these cause a disruption in the processing of signals sent to and from the brain. Examples of these conditions include Parkinson’s disease and motor neurone disease.
- Chromosomal abnormalities: these are genetic conditions that are caused by mutations in the chromosomes or as a result of a baby inheriting the wrong number of genes from their parents. Examples of chromosomal conditions include Down’s syndrome and Williams syndrome.
- Metabolic conditions: these are conditions that disrupt the normal functioning of the metabolism; examples of these conditions include rickets and congenital hypothyroidism (an underactive thyroid gland)
- Connective tissue conditions: these conditions affect the production of healthy connective tissue. Examples include Marfan syndrome and Ehlers-Danlos syndrome.
- Cerebral hypotonia: this type of condition usually occurs as a result of trauma (usually an accident or direct blow to the head); it causes damage to the brain.
Symptoms of hypotonia
Symptoms vary according to the nature of the condition:
Acute hypotonia: these symptoms affect children; they are usually visible by the time a child is 6 months old:
- Difficulty supporting their head
- The child feels floppy and very light
- Difficulty feeding
- The child’s legs and arms fall straight down from their joints, rather than being bent at the knees and elbows
- The child cannot bear weight on their leg or shoulder muscles
- Slower development (in terms of movement; it may take longer for them to sit up, crawl and walk, for example)
Acquired hypotonia: symptoms may appear quickly or over a long period of time:
- Being clumsier than normal
- Difficulty stretching and reaching
- Falling over frequently
- Having difficulty sitting up from a lying position or standing up from a sitting position
Treatment for hypotonia
If hypotonia has been caused as a result of an infection or injury, this will be identified and treated as quickly as possible. If the cause is not treatable measures will be taken to ease symptoms and make life as manageable as possible; common methods include physiotherapy and occupational therapy. Physiotherapy is a very effective treatment; it enables patients to gradually increase their muscle tone and the range of movement around their joints. Occupation therapy aims to teach people to manage their symptoms and maintain a degree of independence.