What is it?
Hypotonia is a medical term used to describe decreased muscle tone. Typically, even when relaxed, muscles have a very small amount of contraction that gives them a springy feel, provides some resistance to passive movement and keeps them ready to move.
It is not the same as muscle weakness, although the two conditions can co-exist. Muscle tone is regulated by signals that travel from the brain to the nerves and tell the muscles to contract. Hypotonia can happen from damage to the brain, spinal cord, nerves, or muscles. The damage can be the result of trauma, environmental factors, or genetic, muscle, or central nervous system disorders.
For example, it can be seen in:
- Down syndrome, muscular dystrophy, cerebral palsy, Prader-Willi syndrome, myotonic dystrophy, Tay-Sachs disease and various other conditions. Sometimes it may not be possible to find what causes the hypotonia.
Other symptoms of hypotonia include problems with mobility and posture, breathing and speech difficulties, ligament and joint laxity, and difficulty with acquisition of gross motor skills. Hypotonia does not affect intellect. The opposite of hypotonia is hypertonia.
Benign congenital hypotonia is normally discovered sometime in the first few weeks of life or within the first two years depending on the severity.
What are the symptoms?
BCH is normally discovered within the first few months of life. Or rather, symptoms are noticed within a few weeks to a year (sometimes with a provisional label of “failure to thrive”).
• Hypermobility of joints. Hypotonic children often find it comfortable to sit in the “W” position and atypical postures that might appear painful to others without the laxity in their joints and muscles.
• Depending on the severity it can result in unusual movement patterns such as maintaining a wide base of support, locking of joints, scooting on the bottom (instead of four point crawling) and difficulty with upright postures such as independent standing and walking. In children with milder symptoms it impacts the ability to perform high level gross motor activities such as balance on one leg, stairclimbing, jumping and hopping.
• The infant or child may feel like they could slip through your hands when you pick them up.
• Poor sucking, swallowing and feeding
• Delayed gross motor, fine motor, and speech acquisition
• Constipation for those whose bowel muscles are affected
How is it treated?
When hypotonia is caused by an underlying condition, that condition is treated first, followed by symptomatic and supportive therapy for the hypotonia. Physical, occupational and speech and language therapy may be recommended to address hypotonia.
The main of objectives of physical therapy will be to improve posture and co-ordination to compensate for low muscle tone and strengthen the muscles around the joints of the arms and legs so they provide more support and stability. Equipment to help you move around more easily may also be recommended, such as ankle or foot supports if your ankles or feet are affected by hypotonia.
In occupational therapy emphasis will be placed on the skills needed to carry out day-to-day activities. For example, the occupational therapist may focus on improving the hand and finger skills needed for dressing and feeding. In addition, OT will also address sensorimotor issues such as body awareness and motor planning.
A speech and language therapist can assess feeding and swallowing, and help identify swallowing and feeding problems that can sometimes be associated with hypotonia. They will work on strengthening and activation of the muscle related to oral motor control, so important for feeding and speech.
The SLT will also be able to make recommendations about feeding support.
Here is a great blog written by a mom whose child has hypotonia: