What is hypotonia (low muscle tone)?
Muscle tone refers to the amount of tension within a muscle when it is at rest. We need a certain amount of tension to maintain an upright posture and move around. Sometimes a person’s muscle tone is either too high (hypertonia), which appears as excessive stiffness, or too low (hypotonia), which appears as floppiness.
When the resting tension in a person’s muscles is lower than normal, the person is considered to have hypotonia. The severity of hypotonia can range from mild to severe. Hypotonia is different to muscle weakness, but often babies and children with hypotonia also have weakness.
What are the signs of hypotonia?
Some of the signs of hypotonia in babies include:
The baby feels floppy or limp to handle
Having little/no control over the neck muscles, which makes the head flop
Not bending and lifting the arms and legs when laying on their back
Difficulty feeding
A weak cry
Not taking weight through the feet (4+ months of age)
Hypermobile (very flexible) joints
Some of the signs of hypotonia in toddlers and older children include:
Delayed gross motor skills (e.g., not sitting by 10 months, not trying to stand up by 12 months, not walking by 18 months)
Fatiguing quickly, needing regular breaks during physically demanding tasks
A preference for more sedentary activities
Bottom shuffling rather than crawling, walking late
If the muscles of the mouth are affected, the child may have delayed speech
Rounded shoulder posture
Difficulty maintaining an upright posture for long periods of time
Hypermobile (very flexible) joints
What causes hypotonia?
Hypotonia is a symptom rather than a condition itself. There are many different causes of hypotonia such as infection, underlying genetic, neurological, or muscle disorder. Sometime it occurs on its own, which is referred to as Benign Congenital Hypotonia. Babies born prematurely sometimes have hypotonia because their muscle tone is not fully developed when they are born.
Do children grow out of it?
Whether or not a child grows out of hypotonia depends on the underlying cause (if any). If there is an underlying cause that can be treated, such as an infection, then the muscle tone will often improve. Babies with Benign Congenital Hypotonia can often improve as they grow, but mild weakness may persist into adulthood. When there is an untreatable underlying condition, hypotonia may not resolve, but there are many ways in which low muscle tone can be managed.
How is hypotonia treated?
Treatment for hypotonia depends on the underlying condition (if any). Building strength is an important part of managing hypotonia and maximising the strength of the muscles will help to make the symptoms of hypotonia less obvious. A paediatric physiotherapist can work with you and your child to design a program of play-based activities that develop gross motor skills, improve posture and increase muscle strength and endurance.
References
Weber, A. & Martin, K. (2014). Efficacy of orthoses for children with hyptonia: a systematic review, Paediatric Physical Therapy, vol. 26, no. 1, pp. 38-47. doi: 10.1097/PEP.0000000000000011.
Mintz-Itkin, R., Lerman-Sagie, T., Zuk, L., Itkin-Webman, T. & Davidovitch, M. (2009). Does physical therapy improve outcome in infants with joint hypermobility and benign hypotonia? Journal of Child Neurology, vol.24, no.6, pp 714-719, doi:10.1177/0883073808329526.
Carboni, P., Pisani, F., Crescenzi, A., Villani, C. (2002). Congenital hypotonia with a favourable outcome. Pediatric Neurology, vol. 26, no. 5. pp. 383-386.
Bodensteiner, JB. (2008). Evaluation of the hypotonic infant. Seminars in Pediatric Neurology, vol. 15, no. 1, pp. 10-20. doi:10.1016/j.spen.2008.01.003