What is all this talk about tone?
Imagine you are walking outside on a cold fall day and a strong gust of wind blows, throwing you a little off balance. Do you fall? Most likely not. The reaction that your body has, of readjusting your muscles to maintain your balance, is due to your muscle tone. Muscle tone has nothing to do with being strong. It has to do with the way the nervous system judges where your body is in space and reacts when a force is placed on the body (like the force of the wind blowing). Tone is also important when your muscle is stretched or when your body changes directions. Tone is the way your body protects your muscles from over stretching when they are relaxed or when they are pulled by movements such as twisting or lunging. Your muscles have an acceptable range of contraction and relaxation. If they relax too much, they may stretch too far. If they contract too much it can lead to painful and debilitating muscle deformities. Tone is basically the monitoring system in the muscle, governed by the nervous system, that maintains your balance, posture and protects your muscles during movement.
So why does it feel like I'm holding limp spaghetti when I carry my baby around?
Eighty percent of babies who have WS have very low tone in the central core muscles of their bodies up until late childhood. Hypotonia or low tone means that children with WS do not react quickly enough to forces that throw them out of balance. The nervous system doesn't communicate with the muscle properly to maintain a contraction for long enough. Basically, the muscle relaxes before it should and is often stretched beyond a normal limit.
The cause of hypotonia can lie in the nervous system pathways. Your nervous system relies on receiving sensory information from the environment. Sometimes children have a deficiency in the sensory input being received by the brain. The brain doesn't receive the messages about where their body is in the environment (related to balance or force being put on the body). The problem may also lie in the motor response. The brain may process the sensory information but then has an issue talking to the muscles and directing the proper response.
What you get, then, are muscles that appear floppy or soft. In fact, this condition is often called "floppy baby syndrome". Babies with hypotonia will have a hard time gaining head control, won't put pressure on their feet to stand and will often lay with their limbs to the side. When a baby is born, an apgar score will be assigned to them to rate their health. One of the conditions in an apgar score is the baby's tone, judged as in the following picture. As the child ages, they will often W-sit (see below) because the muscles in their core are not toned enough to support their posture.
A child who is hypotonic will most often develop late. Therapy is the best method to help the child overcome hypotonia. Physical therapy will help the child coordinate large or gross muscle movements such as pushing up, rolling over, sitting, crawling, walking, climbing, etc. Occupational therapy deals with fine muscle movements like using the pincher grasp to self feed, holding a pencil, manipulating an object into a hole, etc. Both of these types of activities are affected by hypotonia. Speech and feeding can also be affected by tone. The muscles in the mouth, vocal cords and jaw need to have proper coordination with the nervous system to chew, suck, swallow and speak. Therefore, many children with WS receive speech therapy, some far before they ever talk. Children may also need to see orthopedic surgeons to monitor their tone. They may need some orthodics such as shoe inserts or braces on the legs to improve posture and gait. Reference: http://www.atotalapproach.com/index.php/programs/10-programs/25-physical-therapy
Banning the W-sit
Many parents of children with hypotonia see the W- sit frequently. Children who W-sit usually have low tone, hypermobile joints and trouble with balance. Like mentioned above, it helps a child with low tone anchor their body and relieve the muscle exertion placed on the core muscles in the trunk of the body. It also allows them to get close to toys and books. The problem with this position is that it limits the body's ability to turn and twist in order to reach across the body for a toy. These complex movements develop a child's ability to balance, navigate outside on a variable surface and use the brain in a different way- by crossing across the body, the brain is challenged to think in a new way. Therefore, allowing a child to W-sit can ultimately affect their motor development later in life.
Interestingly enough, it can also influence the child's hand preference. If the child isn't crossing the body to reach for toys due to the W-sit, often they will not develop the skill of working through movements across the body, effecting hand preference. If they want something from the left, they use their left hand. Need something from the right? They use their right hand. This can ultimately affect their writing abilities.
W-sit can also affect the the health of their hips later in life. It can lead to hip dislocation and hip dysplasia (improper fit of the leg bone or femur into the hip; causes arthritis). It can cause sway back (coming soon in Part 2 of this page), weak and tight muscles in the lower back and hamstrings, and their feet may begin to turn in when walking.
Why is my child so flexible?
More common than hypertonia, individuals with WS also have a musculoskeletal issue that is called joint hypermobility. Commonly called double jointed, this condition is when some joints, especially those in the hips, knees, fingers and elbows, move at angles that are beyond a typical range. You can find many people in the general population with hypermobility. I'm sure the majority of people have gawked at the kid on the playground folding his thumb backwards or twisting his arms in a knot behind his back. While hypermobility is found in about 10-15% of the general population, 90% of individuals with WS have this condition from infancy through childhood. The reason our little ones are more likely to have this is due to the missing gene, ELN or elastin.
The cause is due to a variation in how the connective tissue is made in the joint. The reason hypermobility is so common in WS is due to the missing elastin gene. Elastin is a stretchy protein and it is an important component of the connective tissues that support our joints- the tendons and ligaments. When the body builds a connective tissue, such as a tendon, it lays down a mesh work of fibers that acts like the foundation. Then, the body builds on that matrix to create the tissue itself. This mesh work or matrix is made of elastin and various other proteins.
Elastin affects the tendon's overall structural make-up, effecting it's function as well. Tendons and ligaments both have a common function. They wrap and support the joint by connecting the bones that form the joints to either another bone (ligaments) or to a muscle (tendons). Both of these tissues are very strong- if you've ever eaten a chicken wing and tried to eat the end of the drumstick that is very tough, you were chewing on a ligament. The toughness makes it strong, but they are also stretchy so that your joint can provide movement. That stretchy quality is due to elastin.
Part 2: Muscle issues of late childhood and adulthood- When things get tight
When most children with WS start their lives with the loose joints and floppy muscles, it can take a parent by surprise when the muscles start to get tight. According to the pediatric guidelines, 50% of individuals with WS experience the excessive tone but other medical journals associate it with 85% of adults. Without proper care, it can lead to some serious debilitating complications such as joint deformities. According to leading WS experts, stretching and therapy to prevent high muscle tone is one of the most important preventive measures (besides cardiology appointments) that a parent can take to protect the health of their child.
Like hypotonia or low tone, having high tone has more to do with miscommunication between the nervous system and the muscle. Remember when we discussed low tone, the brain wasn’t feeding enough information to the muscle to keep it in a state of mild contraction. In high tone, the opposite happens. The muscle receives information from the brain telling it to contract or tighten to a state where it becomes stiff. Over time the stiff muscle can become short and unable to stretch.
When we discussed hypotonia or low tone, we said that it was a measure of how the muscle stays slightly contracted when at rest. In hypertonia or high tone, it has more to do with how the muscle reacts when it’s at work. When an external force is placed on the muscle such as gravity from a hill, the body reacts with an excessive contraction than is needed. This can lead to feelings of stiffness and tightness and can eventually lead to joint limitations. Many people with hypertonia don’t realize there is an issue. It may or may not cause pain and discomfort and they may adapt their gait (the way they walk) to make the muscle use more comfortable or to gain better information about their surroundings.
Some children and adults who have hypertonia have no symptoms except for awkward gait. If they are not assessed by a physical therapist and undergo stretching, the hypertonia can lead to many issues such as painful muscle spasms and fixed joints. Hypertonia can also be aggravated by cold weather, fatigue and multi-task activities. Many kids will complain of the painful muscles at bed time when they are most tired.
Deep Tendon Reflexes
Remember when you would go to the doctor for a physical and they would bring out the reflex hammer to check your reflexes? This simple test would alert a pediatrician or clinician of high or low tone in the muscles. When the doctor taps your tendon with the hammer, it causes the tendon to stretch and results in an involuntary movement or reflex. Reflexes are controlled by your spinal cord or the base of your brain. Information about the stretch in the tendon is picked up by a sensory receptor. This sensory nerve delivers information to your central nervous system about a change in the environment. Unlike other reactions where you put some thought into your body’s reaction, the spinal cord is conditioned to send an immediate response to the muscles in the leg. This causes the muscles to contract and your lower leg to kick.
In a patient with hypertonia, the movement would be exaggerated due to the nervous system over responding to the force of the hammer. If the muscle has high tone, the muscle will overreact by making a vibrating motion called clonus. Alternately, low tone would result in a limited or lack of movement all together by the hammer’s force. Although most of us have only experienced this test on the knee, it can be performed on a variety of tendons including the elbow- to test the biceps and triceps, and at the ankle to test the calf muscles.
Toe Walking- The most common sign of hypertonia
One of the most common first signs of hypertonia is toe walking. Toe walking is considered a very normal part of development in toddlers under the age of 2. When a child is learning to walk, they often will stand on their toes as a way to explore this new motor activity. When toe walking becomes persistent and is seen after the age of 3, then a physical therapist should evaluate the muscles and tendons of the leg. Toe walking after the age of 3 can be a sign of hypertonia and joint contractures.
Why do some kids with WS walk on their toes?
There are a couple of reasons a child with WS may become a toe walker. Some children will start walking in this manner due to high tone in the gastrocnemius and/or soleus muscle, commonly known as the calf muscles. The high tone of the calf makes the muscle shorter, pulling up on the Achilles tendon of the heel. Another reason toe walking can become prominent can be due to behaviors rather than a physical issue. Called idiopathic toe walking, some children will develop a habit where they walk in this manner. Most children with idiopathic toe walking do so because of sensory processing disorders and some will fall on the autism spectrum.
Often children who exhibit toe walking have a sensory processing disorder where they have trouble interpreting their surroundings in regards to balance. The sense of balance is organized by a portion of your inner ear called the vestibular apparatus. Sitting above the cochlea, or “hearing” portion of your ear, are a series of semi-circular canals. These canals are lined with tiny hairs that connect to nerve endings of the vestibular nerve. The tiny hairs are bathed in fluid and are positioned vertically when you are upright. When the body moves, the hairs move with it and activate the nerve. The vestibular nerve then tells your brain what position you are in space.
When you spin around quickly, such as on a carnival ride, those hairs get turned in a variety of different ways and you get dizzy. Your brain cannot interpret where you are in space causing you to walk uncoordinated and the feeling of confusion. The dizziness lasts until the hairs reposition themselves allowing your body to understand how to coordinate your muscles. Your vestibular apparatus works with other parts of your body to gain information about your surroundings and send the proper message about balance. Various places on the face such as the jaw, eyes and tongue talk to the vestibular apparatus as well as the soles of the feet, finger tips and palms of your hand. The information from all these locations allows your brain to properly understand which way is up.
Kids with vestibular processing disorders often need extra sensory information from those peripheral or outlying areas of the body to make sense of their environment. These children will often drag their hands along a wall or touch obstacles in order to gain more information for balance. People do this naturally when they lose their balance. You immediately find something to right yourself and provide some support. Kids with sensory processing disorders do this in situations where you wouldn’t normally need help with balance such as walking down a hallway. Toe walking is another adaptation a body makes to provide the vestibular apparatus with more information. When on your toes, more information will be delivered to the vestibular apparatus resulting in the body’s heightened ability to perceive the environment.
Another reason for the vestibular dysfunction stems from inaccurate visual information. The eye sends valuable information to the vestibular apparatus about the environment. When you walk down a hill the visual input of the slope tells your body to adjust how you walk so that you can maintain your balance. Some children who toe walk receive their visual information in a skewed way. Their eyes interpret the center of their body as leaning more forward than they are in reality. This perception makes them think they need to walk leaning forward to maintain their balance and results in toe walking. When the toe walking is caused by visual issues, working with an optometrist and using prisms can often stop the behavior cold.
Why is toe walking such a big issue?
Overtime, the issue can progress to a point that the muscles become asymmetrical. All muscles work in pairs. You have an antagonist muscle coupled with a protagonist muscle. The calf muscle (a combination of the gastrocnemius and soleus muscles), works against the muscle of the shin (called the tibialis anterior muscle). When the calf muscle is contracted, the shin relaxes and vice versa. These muscles coordinate contraction and relaxation to perform the movement of the lower leg. When a child toe walks, the calf muscle is in a constant state of contraction, disrupting the balance between the shin muscle and itself. This leads to balance and coordination issues in the child.
If the child continues to walk in this manner, the ankle joint can become stiff and malformed causing a joint deformity. Deformed joints are called joint contractures. Joint contractures are common in WS with 50% of individuals having issues with this in all stages of life and especially in adulthood. Joint contractures result from a muscle or joint shortening because of increased tone for too long. Therefore contractures are shrinking or shortening of the muscle or joint. This issue is separate from tone although it’s typically a result of having too much tone in a muscle. Because the joints are made of connective tissue, one being elastin, contractures in individuals with WS is often found in tendons and joints causing additional issues with the shortening of the muscle. In toe walking the contracture occurs in the ankle but in WS contractures can happen in other places where muscles are tight. Most often contractures occur in the wrist, elbows, hands, hips, knees and ankles in individuals with WS.
Treating toe walking
Treatment should involve a physical therapist who will prescribe daily exercises to stretch the tendons and muscles to prevent cramping and contractures. The most effective stretches use the patient’s body weight. Have the child stand on the edge of a step, stool or block and let their heel drop behind. A caregiver can provide stabilization while the weight of the body places a deep stretch on the calf muscle. Stretching is beneficial and typically the first form of treatment but if it is not done daily it can be ineffective.
Serial casting is the most effective form of therapy for calf muscle contractures. The patient will be fitted for an orthotic that places the foot in a flexed state. The casting continually provides a stretch to the muscle. The casting can be adjusted over time as the muscle becomes less tight. This form of treatment should not be used for prolonged periods of time because it can actually make the muscle weaker and cause additional issues.
Other orthotics or braces, called MAFO’s, can be worn while the child is walking. These hold the ankle in the proper position to provide stretch to the muscle when the child is walking. The orthotics last for about a year to a year and a half which is the amount of time typically needed to correct toe walking.
If a child's contractures become severe or they don't respond to serial casting the next treatment may be surgery. During surgery, the tendon with a contracture will be surgically lengthened. Usually, the surgeon divides the tendon in half. One section of the tendon is then sewed onto the tendon in a location closest to the bone to achieve its desired length. There are also less invasive approaches to tendon lengthening where the tendon is feathered in three locations to release the tension of the tendon. After surgery, the patient would have to wear a cast for 6 weeks to immobilize the joint and then follow with intensive physical therapy to maintain the tendon length and build strength.
Muscle and joint issues in WS are extremely common and preventable. It is important for an individual to be monitored by a physical therapist and/or orthopedic surgeon to monitor the tone of the muscle and use preventive measures to avoid issues like contractures.