On the Clock
A Look at Genetic Conditions That Cause Delays in Mobility Development
- By Elisha Bury
- Dec 01, 2016
TOY CLOCK: TRANGPHAN/ISTOCK.COM
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
“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
“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
- 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
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),”
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
“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
“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
“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
“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
“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
“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.
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
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 for these conditions doesn’t have to be as tricky as it
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,
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
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
“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
Learn more about genetic conditions that might impact mobility.
This article originally appeared in the Seating & Positioning Handbook 2016-2017 issue of Mobility Management.