Hypotonia is an impairment of the ability to sustain postural control and movement against gravity. Due to poor muscle tone people diagnosed with hypotonia don’t show resistance when joints in their body move. Hypotonia is also known as “floppy infant syndrome”.
Muscle tone is the amount of resistance (tension) to the movement your muscles have at rest. If you relax your left arm and use your right arm to pinch your bicep, the resistance you feel is your muscle tone. For people diagnosed with hypotonia, pinching their bicep would feel soft, without any resistance.
Muscle tone is your body’s response to force and allows you to maintain your posture to sit and use your reflexes, like moving your arms and legs, and helps regulate the function of organs in your body.
If you have poor muscle tone, your arms and legs appear droopy, similar to a rag doll.
Your baby might have trouble sitting upright, keeping their head up and bending their elbows and knees.
Muscle weakness and hypotonia aren’t the same. Muscle weakness is a lack of strength in your muscles and is often a symptom associated with hypotonia.
Hypotonia is present at birth, and the doctors diagnose hypotonia most frequently during early infancy before your child is six months old. It can also affect adults.
The following are common symptoms associated with hypotonia. Each child may experiences symptoms differently. Symptoms vary depending on the underlying cause of the problem.
• Decreased muscle tone, muscles feel soft and doughy
• Ability to extend limb beyond its normal limit
• Weak ligaments and joints. Since the muscles that support the bone joints are soft, there is a tendency for hip, jaw, and neck dislocations.
• Failure to acquire motor related developmental milestones (such as holding head up without support from parent, rolling over, sitting up without support, walking)
• Problems with feeding (inability to suck or chew for prolonged periods). Hypotonic children also have trouble feeding and are unable to suck or chew for long periods.
• Shallow breathing or breathing difficulties
• Mouth hangs open with tongue protruding (under-active gag reflex)
Some hypotonias are not progressive and are of an unknown origin, a condition known as benign congenital hypotonia.
• Central nervous system function and intelligence in children is normal.
• Children with benign congenital hypotonia may not experience developmental delay.
• Some children acquire gross motor skills (sitting, walking, running, jumping) more slowly than most.
A communication error between the pathways that control movement causes hypotonia. These pathways connect the brain, spinal cord, nerves and muscles. Causes of hypotonia include:
• Brain damage or problems with how your baby’s brain formed during fetal development.
• Conditions that affect how nerves communicate with muscles.
• Conditions that affect muscles.
• Conditions that target nerves responsible for communicating to muscles.
• Lack of oxygen before your baby is born or immediately after.
Other Diseases When Hypotonia is a Symptom –
Hypotonia is usually a symptom of another condition. These conditions can be genetic and congenital (present at birth). Some conditions cause damage to nerves and the brain as your baby grows, resulting in hypotonia as a symptom. These conditions include –
• Down syndrome.
• Prader-Willi syndrome.
• Spinal muscular atrophy.
• Tay-Sachs disease.
• Trisomy 13.
• Williams syndrome.
It’s assessed in two ways by doctors –
• Phasic tone: assessed by the response of the muscle to a rapid stretch (tendon reflexes)
• Postural tone: measured by the response of the muscle to a sustained low-intensity stretch (maintaining posture against gravity = significant head lag on pull-to-sit, ragdoll posture on ventral suspension, slipping through the hands when the infant is held under their arms).
To confirm the diagnosis the doctor may order following tests
• CT or MRI scan of the brain
• Blood tests
• Electromyography (EMG) to measure how well the nerves and muscles work
• Electroencephalogram (EEG) to measure electrical activity in the brain
• Spinal tap, which can measure the pressure inside the spine
• Muscle biopsy, when the doctor gets a sample of your child’s muscle tissue to study under a microscope
• Genetic tests
Once the correct diagnosis is confirmed, the cause 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.
No specific therapy is required to treat benign congenital hypotonia, but children with this problem may periodically need treatment for common occurrences associated with hypotonia, such as recurrent joint dislocations.
Hypotonia is a lifelong condition, but muscle tone can improve over time with successful treatment for the underlying condition that caused your baby’s symptoms.
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