Hypotonia is a medical term used to describe decreased muscle tone. Normally, even when relaxed, muscles have a very small amount of contraction that gives them a springy feel and provides some resistance to passive movement. It is not the same as muscle weakness, although the two conditions can co-exist. Muscle tone is regulated by signals that travel from the brain to the nerves and tell the muscles to contract.
Hypotonia can happen from damage to the brain, spinal cord, nerves, or muscles. The damage can be the result of trauma, environmental factors, or genetic, muscle, or central nervous system disorders.
Other symptoms of hypotonia include problems with mobility and posture, breathing and speech difficulties, ligament and joint laxity, and poor reflexes.
Causes of hypotonia
There are several causes of hypotonia, these include genetic conditions, nutritional causes and so forth.
Genetic causes of hypotonia
There are several genetic causes of hypotonia, these include:
Down Syndrome – This is a genetic disease with a chromosomal abnormality where the 21st pair of chromosome has an extra chromosome. This leads to heart defects, mental retardations and other neurological complications.
Prader-Willi syndrome is a rare genetic disease that causes restricted growth and learning difficulties
Tay-Sachs disease is another rare and fatal genetic disorder that causes progressive damage to the nervous system.
Williams Syndrome – is a rare genetic condition that causes defects in development, cordination and language.
Spinal muscular atrophy is an inherited disease that leads to muscle weakness and a progressive loss of movements.
Charcot-Marie-Tooth disease is yet another inherited condition that affects the myelin covering of nerves. Myelin forms a protective covering over all major nerves of the body.
Connective tissue disorders include Marfan’s syndrome and Elher-Danlos syndrome. These are inherited and lead to defects in connective tissues which provide support to other tissue and organs.
Nutritional causes of hypotonia
Some causes of hypotonia are a result of malnutrition, these include:
Rickets – This is caused by vitamin D deficiency
Malnutrition – Malnutrition in the mother as well as the baby or child especially with lack of adequate protein in diet may lead to hypotonia
Causes of hypotonia that involve the brain
Some of the causes of hypotonia involve the brain. These include:
Brain and spinal cord injury that may include bleeding into the brain
Serious infections of the brain and its parts like meningitis or encephalitis
Kernicterus – This condition is severe affliction of the brain of the new born with bilirubin from the jaundice right after birth. It may lead to severe neurological deficits, retardation, seizures and hypotonia or hypertonia (increased muscle tone).
Causes of hypotonia at birth
Prematurity – Babies born prematurely carry a risk of being born hypotonic. The condition often resolves as the baby grows
Hypothyroidism – Lack of thyroid hormone at birth may lead to hypotonia. If severe it may manifest later as Cretinism characterized by coarse facial features, mental retardation etc.
Sepsis – Severe infection in the new born
Other causes of hypotonia include:
Storage diseases – Inherited metabolic diseases that are caused due to lack of certain enzymes.
Congestive Heart failure
Hypoglycemia – Low blood sugar may lead to floppiness of the muscles
Myasthenia gravis – is an autoimmune disease that disrupts signals between nerves and muscles and affects the neuromuscular junction.
There may be weakness and increased fatigue. Babies with mothers who have myasthenia gravis may be born with hypotonia.
Muscular dystrophy is a progressive muscle disease that leads to weakening of muscles and disability.
In adults muscle hypotonia may be seen in Multiple sclerosis where myelin is damaged or in Motor neurone disease that leads to progressive motor nerve damage.
Treatment begins with a thorough diagnostic evaluation, usually performed by a neurologist, including an assessment of motor and sensory skills, balance and coordination, mental status, reflexes, and functioning of the nerves.
Diagnostic tests that may be helpful include a CT or MRI scan of the brain, an EMG to evaluate nerve and muscle function, or an EEG to measure electrical activity in the brain. Once a diagnosis has been made, the underlying condition is treated first, followed by symptomatic and supportive therapy for the hypotonia. Physical therapy can improve motor control and overall body strength. Occupational therapy can help relearn ways to address activities of daily living. Speech-language therapy can help breathing, speech, and swallowing difficulties. Therapy for infants and young children may also include sensory stimulation programs.
Hypotonia can be a life-long condition. In some cases, however, muscle tone improves over time.
To schedule an appointment with a board-certified neurologist call (910) 295-6868 or for more information visit the National Institute of Neurological Disorders and Stroke.