Hypotonia: Description, Causes and Risk Factors:
Hypotonia is a congenital, non-progressive neuromuscular disorder characterized by decreased skeletal muscle tone and generalized muscle weakness. The condition may occur as a disorder of unknown cause, or as a symptom of other neuromuscular diseases.
Individuals with hypotonia frequently suffer from an inadequate gag reflex
and tongue movements. Consequent swallowing and feeding difficulties may be associated with aspiration or gastroesophageal reflux. Weakened respiratory muscles and an impaired ability to cough may lead to the retention of pulmonary secretions and aspirate in the lungs. Concomitant central nervous system disturbances, such as seizures, occur commonly in this patient population.
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. For example, it can be seen in Down syndrome, muscular dystrophy, cerebral palsy, Prader-Willi syndrome, myotonic dystrophy, and Tay-Sachs disease. Sometimes it may not be possible to find what causes the hypotonia. Infants with hypotonia have a floppy quality or “rag doll” appearance because their arms and legs hang by their sides and they have little or no head control. Other symptoms of hypotonia include problems with mobility and posture, breathing and speech difficulties, ligament and joint laxity, and poor reflexes. Hypotonia does not affect intellect.
It can be difficult to narrow down the cause of hypotonia, especially in young patients. In some cases, it reflects a neurological problem which can occur anywhere in the brain or spinal cord, but it can also be caused by a myopathy, a problem with the muscles themselves. In cases where the cause is not evident, the condition may be known as “benign congenital hypotonia,” although in fact hypotonia is not always benign in nature.
Risk factors may include:
1. Brain damage or encephalopathy, due to:
- Lack of oxygen before or right after birth.
- Problems with brain formation.
2. Disorders of the muscles, such as muscular dystrophy.
3. Disorders that affect the nerves that supply muscles (called motor neuron disorders).
4. Disorders that affect the ability of nerves to send messages to the muscles:
- Infant botulism.
- Myasthenia gravis.
5. Inborn errors of metabolism (rare genetic disorders in which the body cannot properly turn food into energy).
7. Other genetic or chromosomal disorders or defects that cause brain and nerve damage, such as:
- Down syndrome.
- Prader-Willi syndrome.
- Tay-Sachs disease.
- Trisomy 13.
Other miscellaneous disorders:
- Congenital hypothyroidism.
- Congenital cerebellar ataxia.
- Marfan syndrome.
- Poisons or toxins.
- Spinal cord injuries that occur around birth.
Symptoms may include:
General weakness and flaccidity of the muscles (reduced strength and endurance).
- Depending on the underlying disease, different sets of muscles may be involved.
- Poor reflexes.
- Hypermobility of joints (how far back can you bend your fingers?). Hypotonic children often find it comfortable to sit in the "W" position and other painful or contortionist looking postures.
- Inability to lift the head, rolling instead of crawling (shuffling on their bottoms).
- Physical passivity.
- The child feels like a sack of Jell-O when you pick the child up - he or she wants to slide out of your hands.
- • Poor sucking (and feeding).
- Weak cry.
- Delayed gross and fine motor development.
- Constipation for those whose bowel muscles are affected.
A diagnosis of hypotonia is sometimes considered a form of muscular dystrophy or cerebral palsy, depending on the symptoms and the doctor. If the cause of the hypotonia is thought to lie in the brain, then it might be classified as a cerebral palsy. If the cause seems to be in the muscles, it might be classified as a muscular dystrophy, even though most forms of hypotonia are not seriously dystrophic. If the cause is thought to be in the nerves, it could be classified as either or neither. In any case, hypotonia is rarely an actual muscular dystrophy or cerebral palsy, and is often not classified as either one, or anything at all for that matter.
Diagnosing a patient includes obtaining family medical history and a physical examination, and may include such additional tests as computerized tomography (CT) scans, magnetic resonance imaging (MRI) scans, electroencephalogram (EEG), blood tests, genetic testing (such as chromosome karyotyping and tests for specific gene abnormalities), spinal taps, electromyography muscle tests, or muscle and nerve biopsy.
Mild or benign hypotonia is often diagnosed by physical and occupational therapists through a series of exercises designed to assess developmental progress, or observation of physical interactions. Since a hypotonic child has difficulty deciphering his spatial location, he may have some recognizable coping mechanisms, such as locking the knees while attempting to walk. A common sign of low-tone infants is a tendency to observe the physical activity of those around them for a long time before attempting to imitate, due to frustration over early failures. Developmental delay can indicate hypotonia.
There is currently no known treatment for hypotonia, and objective manifestations can be life long. The outcome in any particular case of hypotonia depends largely on the nature of the underlying disease. In some cases, muscle tone improves over time, or the patient may learn or devise coping mechanisms that enable them to overcome the most disabling aspects of the disorder. However, hypotonia caused by cerebellar dysfunction or motor neuron diseases can be progressive and life-threatening.
Along with normal pediatric care, specialists who may be involved in the care of a child with hypotonia include developmental pediatricians (specialize in child development), neurologists, neonatologists (specialize in the care of newborns), geneticists, occupational therapists, physical therapists, speech therapists, orthopedists, pathologists (conduct and interpret biochemical tests and tissue analysis), and specialized nursing care.
If the underlying cause is known, treatment is tailored to the specific disease, followed by symptomatic and supportive therapy for the hypotonia. In very severe cases, treatment may be primarily supportive, such as mechanical assistance with basic life functions like breathing and feeding, physical therapy to prevent muscle atrophy and maintain joint mobility, and measures to try to prevent opportunistic infections such as pneumonia. Treatments to improve neurological status might involve such things as medication for a seizure disorder, medicines or supplements to stabilize a metabolic disorder, or surgery to help relieve the pressure from hydrocephalus (increased fluid in the brain).
Occupational therapy can be used to assist with fine motor skill development and hand control, and speech-language therapy can help breathing, speech, and swallowing difficulties. Therapy for infants and young children may also include sensory stimulation programs." Ankle/foot orthoses are sometimes used for weak ankle muscles. Toddlers and children with speech difficulties may benefit greatly by using sign language.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.