On the Clock

A Look at Genetic Conditions That Cause Delays in Mobility Development

colorful play clock for children


Children diagnosed with genetic conditions can have symptoms as spiraling and unique as a double helix. Yet sometimes a malfunctioning gene results in the same developmental outcome: mobility impairment or delay. What can be done when the clock is running, but mobility development is slowed? Answering that question with the proper intervention can make all the difference for these children now and in the future.

Mobility Management looks at three genetic syndromes that can lead to full- or part-time mobility equipment use: Angelman, Rett and Down syndromes. Many of these children might eventually walk. Here’s what you need to know to help them become independently mobile or to maximize their mobility potential.

A Look at Angelman Syndrome

The UBE3A gene, or Angelman gene, is located in chromosome 15. A deletion of a section of this chromosome is the most common cause of Angelman, which results in deficient expression of the gene in the brain, according to Angelman Syndrome Foundation.

Children with Angelman are typically diagnosed between the ages of 2 and 5, although symptoms begin much earlier, according to the Angelman Syndrome Foundation. Characteristics usually include developmental delays, seizures, and difficulty with speech development, including lack of cooing and babbling. These children are unusually happy, with frequent bouts of laughing and smiling.

“Developmental delays are commonly seen between the three syndromes (Angelman, Rett and Down),” says Gabriel Romero, VP of sales and marketing at Stealth Products. However, with “Angelman, the inability to walk is more common.”

The reality is that “of the Angelman’s diagnosed customers, 12-15 percent will never be ambulatory,” says Ralph Booker, an ATP with National Seating & Mobility. These children “will need not only a mobility device, but positioning and pressure relief. Of the remainder, the use of a stroller base, manual wheelchair or companion chair will be needed.”

Developmental delays in Angelman have considerable variability, ranging from mild toe-walking to severe impairment. For some, sitting might occur after age 1, and for others walking can be delayed as late as 5 years, according to the Angelman Syndrome Foundation.

“Some children may exhibit hypertonicity, dystonia and/or spasticity early on in their development and not demonstrate any ability to move,” says Karen Kangas, OTR/L, who specializes in pediatrics. “Their own physical characteristics of movement can resemble children who have been diagnosed with cerebral palsy.

“Other children may be ambulatory yet ataxic. Other children may be severely delayed in motor development, spending months or years in an apparent single stage of motor development [and] then change and gain more control,” she says.

Common issues associated with Angelman that impact mobility are seizures, ataxia, hypotonia and kyphotic posture:

  • Ginny Paleg, DScPT, MPT, PT, says that seizures can make unsupported walking unsafe in addition to preventing these children from keeping up with peers.
  • Ataxia can be severe or mild. Mild ataxia appears as forward lurching, balance issues or hyperkinetic movements, especially in the trunk and limbs.
  • Hypotonia is a common symptom, Paleg says. This low tone can severely delay development.
  • Another common issue is kyphotic posture, thanks to mobility equipment limitations, Romero says. In fact, scoliosis is quite common in as many as 80 percent of children with Angelman and might require bracing, according to the Angelman Syndrome Foundation.

In addition, some children with Angelman also experience feeding and speech problems, double vision caused by an inability to align the eyes properly, as well as a myriad of other mobility-related issues, such as uplifted fixed arms during ambulation and a wide-based gait with pronated feet.

Booker adds that those with deletion-positive Angelman are most at risk for hypotonia, feeding disorders and seizures.

Heat sensitivity can also interfere with mobility, says Booker, whose son has Angelman syndrome. As a result, mobility equipment might be needed for outings.

“In my son’s case, his seizures can be set off by heat [because he is] unable to regulate body temperature, [and] exertion fever [from] infection due to ears, wounds, UTI (urinary tract infections),” Booker says.

Retrospective on Rett Syndrome

Unlike Angelman syndrome, Rett syndrome develops after childbirth. The condition stems from a mutation of the MECP2 gene and seems to occur randomly, according to the Mayo Clinic. The mutations affect brain functioning in the areas of learning, speech, movement, breathing, heart function as well as chewing and swallowing, according to RettSyndrome.org. Because many different types of mutations can occur, Rett syndrome symptoms range from mild to severe. Rett syndrome affects girls almost exclusively.

With Rett syndrome, development proceeds typically at first. At around 6 months of age, infants begin to lose skills involving crawling, communicating or using their hands. Changes typically worsen around ages 12 to 18 months. Muscles can become weak or spastic.

“Children with Rett can be slow to walk independently or walk independently and then lose skills,” Paleg says. “New data show that as a teen, if walking is maintained, it can actually get better.” Motor apraxia has a significant effect on mobility, although the results might be quite different among children with Rett syndrome.

“Motor apraxia prevents consistent sensory information to support motor control,” Kangas explains.

Like children with Angelman syndrome, children with Rett experience seizures, loss of muscle control and scoliosis. Unusual eye movements might also impact mobility functioning. Children with Rett are prone to fractures and can have trouble chewing and swallowing. Rett syndrome is also marked by life-threatening heart complications related to an irregular heartbeat.

One characteristic of Rett is the loss of communication skills. Children with this syndrome might stop speaking, making eye contact and communicating non-verbally. Loss of interest in people and surroundings might occur as well as periods of sudden and prolonged agitation and crying. Communication skills can be regained later.

According to the Mayo Clinic, children with Rett experience a lot of pain. Unfortunately, these children might be unable to express this pain.

Although loss of communication skills might not seem tied to mobility, Booker says this symptom is the real key to mastering intervention.

“In all of these diagnoses, it took me too long to realize how much was understood by the customer I was working with,” he says. “The inability to express themselves is the limitation.”

Dealing with Down Syndrome

Down syndrome, by far the most widely recognized among genetic pediatric conditions, occurs because of a full or partial extra chromosome 21. Individuals with Down syndrome present with the easily recognized small stature and upward-slanted eyes. In addition, these children have low muscle tone and cognitive delays, according to the National Down Syndrome Society.

What might not be widely recognized is that delayed mobility development in children with Down syndrome might be caused by cardiac conditions or low muscle tone, according to the National Association for Child Development.

“The most common issue for many children with Down syndrome is hypotonic or low motor tone,” Kangas says. “However, children with this diagnosis still exhibit great variability in their range of tone. Most children with Down syndrome exhibit slower development when gaining independent mobility... What's critical early on is providing children with opportunities to move while engaged in activity.”

Paleg says, “We know treadmill and maybe gait trainer use will lead to sooner achievement of motor milestones and may improve language and cognition. Treadmill training later can improve walking as well.”

Like other genetic conditions, Down syndrome occurs on a spectrum, with mild to severe delays. Children with Down syndrome might eventually reach development milestones, including sitting, standing and walking, according to the American Academy of Orthopedic Surgeons.

Joint instability might impact the ability to walk, as hips, knees and other joints can become dislocated — resulting in falls.

“Protecting a child's skeletal health with Down syndrome is critical as we know many children may have some increased risk in their cervical vertebrae,” Kangas says.

The Case for Early Intervention

Whatever the diagnosis, early intervention could considerably improve outcomes.

“We've known for so many years that if independent mobility does not occur, all areas of development are lost,” Kangas says. She explains that research supports this idea.

Paleg agrees. “The best research says that the critical period for intraspinal neuron plasticity is before 12 months, and that the motor and sensory cortex plasticity peaks at 24 months. This is why you can’t wait until they walk at 15 to 24 months; it’s too late for spatial awareness, initiation [and more],” she says.

So what is the proper age for intervention?

“That's the big question we all have,” Paleg says. “Dale Ulrich has shown increased activity levels for children with Down syndrome who walked early due to treadmill training. We think it also improved spatial awareness, language and cognition. Cole Galloway and Sam Logan introduced power to a toddler who was a great driver, but never quite got the initiation part. Researchers are working hard to show that early mobility is essential, but it’s not so easy.”

Paleg begins at 9 months of age by introducing a stander and gait trainer, but she doesn’t stop there.

“I introduce a toy car or some form of power as well,” Paleg says. “The evidence is not strong but suggests that these interventions spur language and cognition.”

“In any pediatric case, the sooner a child can have access to independent mobility, the more experience they gain in important early development needs they may have,” Romero says.

However, the diagnosis significantly influences when and how mobility devices are introduced. This is especially true for Rett syndrome.

“Motor apraxia can prevent hands from holding on to a mobility device and/or prevent a child from reaching out to explore their environment,” Kangas says.

In fact, children with Rett have a hard time feeling where their bodies are in space, Kangas says. Supporting movement is critical to supporting a child’s development, but for children with Rett, going slowly and providing structure to mobility is key.

Certainly, waiting might be the worst thing for a child with a genetic condition.

“Waiting means lost opportunity to make a better brain. If the CUNY (City University of New York) team is right and the peak time for change has closed by 12 months, then watchful waiting is a lifetime sentence of lost potential,” Paleg says.

Equipment Considerations

While symptoms of Angelman, Rett and Down syndromes may vary, they all have one thing in common: “Loss of normal movement and coordination usually will require some form of mobility assistance,” Romero says.

Paleg describes children with Angelman and Rett syndromes as lean movers and those with Down syndrome as still, short and stout. But, “they all tend to have hypotonia [and] so will sink into any supports,” she says.

Dynamic components work best for these conditions. “I like the KidWalk and the Rifton dynamic activity chair,” Paleg says. “These children are at moderate risk for hip dysplasia. So I would get a stander that abducts 30° to 60°.”

For positioning, Romero says, “With Rett syndrome, the abnormal movements need to be considered in the type of seating and mobility that is prescribed. The kyphotic posture is commonly seen in the three syndromes; consider proper back and seat surfaces and measurements.”

Booker says the type of equipment, as with other conditions, depends on the goals of the entire health team. Mobility providers also must consider the home and school environments as well as transportation.

If the child cannot walk, then Booker might recommend a manual tilt-in-space wheelchair, a positioning back with lateral supports, as well as pressure-relieving devices. Booker also says to account for individual health conditions, including seizures, scoliosis, incontinence and heat dissipation, as well as communication and orthotic devices.

But Kangas warns that children with these diagnoses do not simply need a scaled-down version of adult equipment.

“Mobility devices do not always allow a child to participate in the act of entry and exit. Instead an adult is required to lift and/or place the child in the system,” Kangas says. “For the child with motor apraxia, this can be confusing or anxiety producing. Mobility equipment needs to be readily controlled by a child's body and be very maneuverable.”

For example, Kangas usually recommends powered mobility for children with Rett syndrome, but often this equipment is rejected. Again, Kangas says that assessment for power should be different from an adult assessment.

Usually, “a chair with a joystick or single hand switches is tried in a large gym or big space,” Kangas explains. “This is incredibly confusing for a child with motor apraxia. First of all, eye-hand coordination is the most compromised of all motor processing with apraxia. Then a large space gives no clues as to how the device is to work or a path to follow. However, using electronic switches (zero force) within a headrest within a very structured familiar pathway, working in short routines and in singular directions first has proved successful when the seating and powered chair fit and have been adequately programmed.”

Funding Conundrum

Funding for these conditions doesn’t have to be as tricky as it might sound.

For children with Angelman syndrome, “about 70 percent are prescribed mobility devices in the school setting, and funding in Pennsylvania is good,” Booker says.

He attributes the ability to get funding to the involvement of the school therapist, physical medicine and rehabilitation physicians, and neurologists.

Paleg agrees. “I have never had any issues. In early intervention as well as at school, it is the responsibility for the provider agency to purchase loaner equipment, as per IDEA (Individuals with Disabilities Education Act). We loan out equipment for the family to try and then purchase it after they know what they want or need.”

Paleg says to do what you know.

“Start with a full assessment, [and you] must include two or more ICF [International Classification of Functioning] areas. Use a valid reliable tool, like GMFM-88 (Gross Motor Function Measure). It's all about medical necessity. Make sure you cite real primary research that shows medical need. Leave out all extraneous information. Stick to the point,” she advises.

Sometimes getting funding might require a little coaching of the medical team. Booker explains, “We have a good relationship with our son’s (primary care physician) and neurologist who will write ‘whatever you need,’ but don’t know what to write to satisfy insurance scrutiny. So we need to find a therapist who is not threatened that we know more about our son than they ever will.”

Funding can be a bit tricky as children with genetic conditions grow up.

“It is when they transition out of the school setting when funding becomes difficult,” Booker says. “Therapists in the adult market are unfamiliar with all the issues involved with these diagnoses.”


Learn more about genetic conditions that might impact mobility.




This article originally appeared in the Seating & Positioning Handbook 2016-2017 issue of Mobility Management.

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