Hypotonia, sometimes referred to as floppy infant syndrome, is a condition characterized by the loss of muscle tone. Instead of the normal resistance you would feel when pressing on a muscle, the muscles of children with hypotonia feel soft and doughy. This lack of muscle tone can be disconcerting: a baby with hypotonia will feel limp, almost like a rag doll, when picked up or held.
Although your doctor is likely to quickly identify signs and symptoms of hypotonia, there are other clues you might notice. Your baby might have poor head control or might miss developmental milestones such as rolling over or sitting. Your baby may also have trouble feeding, have shallow breathing, or have a hypotonic gag reflex that causes the mouth to hang open with the tongue sticking out.
Hypotonia in an infant is a symptom that can be related to various conditions, including:
- Cerebral palsy or any brain damage that develops from lack of oxygen to the brain at birth.
- Spinal cord injuries that occur at birth.
- Serious infections, such as meningitis, encephalitis, or infant botulism.
- Genetic conditions such as Down Syndrome, Prader-Willi, or many other chromosomal problems.
- Endocrine or metabolic problems such as hypothyroidism or inborn errors of metabolism.
- Nerve or muscle disorders such as Muscular Dystrophy, Myasthenia Gravis, or Guillaine-Barre syndrome.
There are likely to be other symptoms occurring that will help your doctor figure out which disorder is causing the hypotonia. Your doctor may determine that your baby needs to be evaluated immediately if an infection or metabolic cause is suspected that can be treated right away. If your doctor determines that the cause of the hypotonia stems from a chronic condition, you will be asked about your family’s medical history to help nail down the cause. The pediatrician will likely consult a neurologist to conduct a detailed physical examination to test nervous system and muscle function. Your baby may be sent to other specialists, including a geneticist, endocrinologist, or orthopedic doctor, depending on the suspected cause. Other tests may include a CT scan, MRI, EEG, chromosomal studies, or a muscle biopsy.
Once the diagnosis is made, the underlying cause of this disorder is treated first. Your child may also need physical therapy, occupational therapy, sensory stimulation programs, and speech therapy. Children with this disorder should be handled gently to avoid injury. Since their muscles are so soft, they can be prone to dislocated joints. In some cases, hypotonia can be a lifelong problem; however, muscle tone is sometimes improved through therapy and treatment of the underlying disease.
Reviewed by Dr. Sara Connolly, April 2019