People with hypotonia lack the normal amount of muscle tone; in other words, their muscles are too relaxed and cannot contract sufficiently. Hypotonia is the opposite of hypertonia, a condition marked by too much muscle tone. However, some individuals may have both hypertonia and hypotonia – the conditions are not mutually exclusive.
Although hypotonia can emerge later in life, it is usually recognizable starting in infancy. Babies with hypotonia may appear “floppy” and fail to meet developmental milestones. Sometimes hypotonia resolves on its own, but it is often an early sign of a disability such as cerebral palsy.
Causes of Hypotonia
Hypotonia can be a symptom of many different underlying conditions. For example, ataxic cerebral palsy is characterized by hypotonia. People with athetoid/dyskinetic cerebral palsy often experience both hypotonia and hypertonia, as do people with “mixed” cerebral palsy. Hypotonia can also be caused by hypoxic-ischemic encephalopathy (HIE), as well as meningitis and other serious infections. Genetics may also occasionally be a cause.
Sometimes, premature babies have hypotonia simply because their muscle tone is underdeveloped. This problem may resolve with time. However, clinicians should still take signs of hypotonia in premature infants seriously, because premature babies are very vulnerable to birth injuries and at high risk of developing conditions like cerebral palsy.
Signs and Symptoms of Hypotonia
Hypotonia is often recognized by the time a baby is six months old, and in severe cases, it may be apparent much earlier than that. Signs of hypotonia in infants include:
- Flopping head due to lack of neck muscle control
- Buckling under their own weight
- Difficulty sucking or swallowing
- Unusually quiet vocalizations (such as a soft cry)
- Delays in reaching developmental milestones like sitting upright, crawling, walking, or speaking
Older children and adults with hypotonia may be unusually flexible, clumsy, have difficulty getting up from a lying or sitting position, and in some cases struggle with reaching or lifting objects.
Infants showing signs of hypotonia should be referred to specialists who can diagnose the underlying cause. They might need to do blood work, or take images with computerized tomography (CT) or magnetic resonance imaging (MRI) scans.
Treatment of Hypotonia
The appropriate treatments for an individual with hypotonia are often based around addressing its underlying cause. For example, if an infant with hypotonia has an infection, that infection should be treated. Certain causes, such as cerebral palsy, are not curable. However, there are many types of treatments and therapies that may alleviate the symptoms. Please note that treatments for cerebral palsy differ depending on subtype; treatments for spastic cerebral palsy may not be appropriate for someone with hypotonia.