What is Hypotonia?
The term “hypotonia" is used to describe the condition of low muscle that is associated with various developmental disabilities such as Downs, Fragile X Syndrome and some types of cerebral palsy. Sometimes the term is used alone as a diagnosis when the child has motor delays that impact function. However, hypotonia is not a medical disorder but rather a symptom associated with decreased strength and postural control.
What is Muscle Tone?
We all have muscle tone. It is the amount of tension in our muscles. Babies with low muscle tone appear to be floppy. Their limbs don’t feel like they are offering resistance when moved. Hypotonia impacts muscle control—making it difficult for a:
- Four month old baby to lift his head while on his belly
- Six month old baby to be held in the air like an airplane with arms and legs extended
- Seven month old baby to sit independently
- Eight month old baby to crawl
Babies with hypotonia typically also have difficulties learning to suck, chew foods and speak because the low tone around and inside the mouth forces them to put a lot more effort into these motor tasks and they quickly fatigue. They may also have muscle weakness, decreased sensation and poor coordination that impacts oral motor development. Babies develop motor skills from head to toe. The eyes and the neck are the first parts of the body that the baby learns to control and difficulties with stabilizing the head in order to look around may be an early sign of hypotonia.
The Impact of the Vestibular Sense
Infants have brains that are wired to respond to the pull of gravity. The vestibular sense organs inside the inner ears respond to movement as the baby works against the pull of gravity to hold her head up and eventually roll over, sit and reach for objects. The vestibular sensory system is responsible for muscle tone and parents can observe this when an unexpected, startling movement makes a baby stiffen whereas, repetitive, slow, swaying movements relax her muscles.
Babies with hypotonia often have joint hypermobility which means that they can easily move beyond normal range of motion and are at risk of joint dislocation. Infants should be positioned on their backs with rolled up towels or small cushions to keep their hips in place (avoiding over stretching). Spending time on the belly is very important for motor development, but babies with low muscle tone may need to be assisted with a small pillow under the chest so that they can put weight on their forearms and eventually hands– leading up to crawling. Babies can practice sitting while positioned in a corner using the two walls or cushions for support. Stimulating visual toys can be used to encourage holding these positions while developing neck and trunk strength.
The Hypotonic Toddler
A toddler with hypotonia should be encouraged to crawl even after she has learned to to walk or run. Crawling develops strength, coordination between the right and left sides of the body and promotes visual skills as the child works to hold her head up against the pull of gravity and views the world from a different perspective. Parents can create play environments that motivate crawling by placing toys inside play tunnels or invite an older siblings to role model being a pretend dog or cat. Young children with hypotonia seem to tire quickly, lean against walls, slouch and slide out of their seats. Provide a chair with arms or one that can be pulled inside a circular opening at a table. Be sure that the height of the chair is adjusted so that child sits with hips, knees and ankles at ninety degree angles with feet flat on the floor. Activities with fast movement such as jumping on a small trampoline, swings and bouncing on top of a therapy ball help to increase muscle tone. Toys that involve sucking or blowing such as bubbles, whistles or straws and eating crunchy foods help to increase muscle tone around the mouth and squeeze toys such as squeaky balls or playing with putty help to increase muscle tone in the hands.