Hypotonia is a medical condition characterized by low muscle tone and poor muscle strength. Although not a specific medical disorder, it can be considered to be a manifestation of different ailments affecting motor control and muscular development. Though the signs of hypotonia are easily identifiable, the underlying causes can be hard to pinpoint, making treatment a challenge. Hypotonia can be caused by conditions both congenital and acquired. Down syndrome, achondroplasia, Krabbe disease, and Leigh’s disease are instances of congenital hypotonia. Acquired hypotonia is commonly caused by muscular dystrophy.
Symptoms of hypotonia
Hypotonia has several well-defined symptoms, the most prominent among them being:
Reduced Muscle Definition: This is possibly the surest symptom of hypotonia. Weak underdeveloped muscles point towards a disorder – neurological or muscular – that has progressed into hypotonia.
Delayed Reaction to External Stimuli: Slow reflexes also send a warning signal in this direction. Mental retardation due to any disorder tends to make patients dull and unresponsive to surprise, pain, or other overwhelming emotions.
Floppy Baby Syndrome or Infantile Hypotonia: The disorder can be diagnosed in infancy when the baby shows signs of low muscle tone and is floppy like a rag doll. They are unable to keep their limbs flexed or extended for long periods of time. Breastfeeding can be a problem due to the child’s weak orbicularis (mouth muscle).
Drooling, speech impediments, and learning disabilities also signal the possibility of hypotonia. As children grow older, they begin to flex and stretch their limbs to perform more complex tasks which require a rapid increase in muscle tone. Children suffering from hypotonia are unable to keep up as their muscles, ligaments and joints do not develop sufficiently. They face challenges in learning to crawl, walk, lift their hands or balance their heads. Any activity that requires motor skills becomes tough and requires therapy to learn.
Causes of hypotonia
Hypotonia can be caused by any one or a combination of various disorders.
Krabbe Disease: A rare, fatal disease, it affects the nervous system and leads to progressive degeneration of nerve control and bodily functions. Infants may appear normal at birth, but begin to show symptoms like fever, vomiting and seizures when they are between 3 to 6 months old.
Down Syndrome: One of the most common disabilities in human beings, Down syndrome is characterized by retardation in physical and mental growth. Though, patients can live better lives with therapy and education.
Achondroplasia: An anomaly in the DNA causes dwarfism in patients of achondroplasia. It can be diagnosed prior to birth, but has no treatment as yet, and adults are of a short height, averaging just about 50 inches.
Menkes Syndrome: This was discovered by John Hans Menke in 1962, and is characterized by poor mental development, frequent seizures, and hypotonia. It results from a genetic mutation, due to which the body is unable to maintain the required levels of copper. This affects the development of the skin, bones, hair growth, and also the blood vessels that service the brain.
Muscular Dystrophy: A group of diseases that leads to muscle waste and atrophying, becoming progressively worse with time, causing weakness and eventually death. It is a common cause of hypotonia.
Celiac Disease: It occurs due to the genetic makeup of the patient, and is characterized by weakness, prolonged nausea, and it may even affect other organs in the body. Treatment of Celiac disease is done by administering the patient a gluten-free diet, as it affects the small intestine. Adherence to such a diet gives the intestines time to recover.
Rickets: This is a disease that primarily affects children, and is caused by the deficiency of vitamin D in the body leading to weakening of bones and other skeletal disorders. An infusion of vitamin D or calcium is helpful in combating the illness. If left unchecked, rickets can cause hypotonia.
Diagnosis of hypotonia
An initial diagnosis of hypotonia can be made by physical examination of the patient and the presence of the more obvious signs of the disorder such as low muscle tone, poor reaction time, slurred speech, or in case of an infant, its difficulties in breastfeeding. Hypotonia is considered to be cerebral palsy when it affects the brain and muscular dystrophy when it affects the muscles.
A more comprehensive diagnosis would involve several tests like:
- CT scan
- MRI scan
- EEG (Electroencephalogram)
- Genetic testing (which involve testing for abnormalities in genes, chromosome karyotyping, etc.)
- Blood test
- Electromyography muscle test, muscle and/or nerve biopsy
- Spinal taps (extraction of spinal fluid for analysis)
Treatment of hypotonia
There is no known and approved treatment available to cure hypotonia. However, depending on the diagnosis, a two-pronged strategy of medication and supportive therapy can be adopted. Children can be put under the care of a physiotherapist who charts out an exercise regimen to develop muscle strength and speech. Occupational therapists can be helpful in managing learning disorders. Acupuncture is used in some cases to help rejuvenate atrophied muscles. Electrical neuromuscular stimulation is sometimes advised for patients who also have weak muscles in addition to low muscle tone. Continuous therapy, care and exercise have helped patients lead fuller lives despite the often debilitating conditions that cause hypotonia.