resources
NATIONAL and STATE of KENTUCKY RESOURCES
www.ndss.org –
National Down Syndrome Society
www.ndsccenter.org –
National Down Syndrome Congress
Medical information
Atlantoaxial Instability (AAI) denotes
increased mobility at the articulation of the first and second
cervical vertebrae (atlantoaxial joint). The causes of AAI are
not well understood but may include abnormalities of the
ligaments that maintain the integrity of the articulation, bony
abnormalities of the cervical vertebrae, or both.
In its mildest form, AAI is asymptomatic
and is diagnosed using X-rays. Symptomatic AAI results from
subluxation (excessive slippage) that is severe enough to
injure the spinal cord, or from dislocation at the atlantoaxial
joint.
Approximately 15% of youth with DS have
AAI. Almost all are asymptomatic. Some asymptomatic individuals
who have normal X-rays initially will have abnormal X-rays
later, and others with initially abnormal X-rays will have
normal follow-up X-rays; the latter change is more common.
The neurologic manifestations of
symptomatic AAI include easy fatiguability, difficulties in
walking, abnormal gait, neck pain, limited neck mobility,
torticollis (head tilt), incoordination and clumsiness, sensory
deficits, spasticity, hyperreflexia...and {other spinal cord}
signs and symptoms. Such signs and symptoms often remain
relatively stable for months or years; occasionally they
progress, rarely even to paraplegia, hemiplegia, quadriplegia,
or death. Trauma rarely causes the initial appearance or the
progression of these symptoms. Nearly all of the individuals
who have experienced catastrophic injury to the spinal cord had
weeks to years of preceding, less severe neurologic
abnormalities....
Most importantly, symptomatic AAI is
apparently rare in individuals with DS. In the pediatric age
group, only 41 well-documented cases have been described in the
published literature.
Asymptomatic AAI, which is common, has not
been proven to be a significant risk factor for symptomatic
AAI.
The efficacy of the intervention to prevent
symptomatic AAI has never been tested. Sports trauma has not
been an important cause of symptomatic AAI in the rare patients
with this disorder; only 3 of the 41 reported pediatric cases
had initial symptoms of AAI or worsening of symptoms after
trauma during organized sports participation. Members of the SO
Medical Advisory Committee think that more such sports-related
injuries occur but that they are being overlooked because of a
lack of information about the association of AAI and spinal
cord injury among health care providers. This claim has not
been substantiated with published research.
The small bowel has many roles, one of
which is to absorb nutrients from our food. Celiac disease (CD)
arises when the lining of the small bowel becomes damaged from
exposure to gluten, the protein found in wheat, barley and rye.
(Oats may be involved because oats are often contaminted with
gluten from other grains during the milling process.) The small
bowel becomes unable to absorb water and nutrients, causing a
number of different symptoms.
Why does a child get CD? First, the disease
arises only after exposure to gluten. Second, there is usually
a genetic predisposition toward a "sensitive" small
bowel lining. Third, certain environmental insults may make the
lining more susceptible to injury from gluten, such as surgery
on the gastrointestinal tract or a gastrointestinal infection.
Whatever the initial reason, the gluten causes an immunologic
response in the lining of the small bowel: the surface folds
shrink and flatten and a "malabsorption" condition
occurs. CD used to be considered to be much more common in
Europe than in the US, but recent studies indicate that the
incidence of CD in people in the US of European ancestry have
the same incidence as in Europe. People of African-Caribbean
and far Eastern Asian ancestry very rarely have CD.
Studies in the 1990s indicated that
children with DS are at a higher risk to develop CD than the
general population. The reasons for that aren't entirely clear,
but since children with DS are at a greater risk from
auto-immune diseases, that CD represents another one of these
type of diseases. Studies from Europe looking at the percentage
of children with DS that have CD have ranged from 7% to 16%.
One American study found 4 to 5% of children with Down syndrome
living on the East Coast had positive CD, but almost all the
subjects were Caucasian, so this group was mostly of European
heritage to begin with. Another American study done in the
southeastern US found 7% of the children with DS studied had
CD.
The signs of CD are varied, since the
condition may be mild in some and severe in others. The
majority of children with CD have what's called "failure
to thrive:" lack of growth of weight, and sometimes height
as well. Most have diarrhea, and/or vomiting. Children with CD
are irritable and usually have a decreased appetite. The stools
may be foul smelling, and in occasional cases, may not be loose
but big and bulky. A small number of children will develop
severe diarrhea leading to dehydration. The children who have
had CD for several months will have bloating of the stomach and
a loss of muscle mass. If not treated, malabsorption will
continue to cause undernourishment, producing anemia,
osteoporosis and peripheral neuropathy.
The main way of diagnosing CD has always
been through biopsy of the small bowel. Under a microscope, the
small bowel will show characteristic damage to the lining. One
way this is done by having the patient swallow a capsule
attached to a string, which is used to retrieve the capsule
after a period of time. Many doctors prefer to do a biopsy
under direct endoscopy, however, especially in children. The
lining of the small bowel has certain characteristics under a
microscope when CD is present.
Since a small bowel biopsy is neither easy
nor cheap, it's not in the best interest of the child or family
to do a biopsy on every child with DS. So the best thing would
be to have an easy blood test that can detect the children who
need the diagnostic biopsy. A few blood tests have been tried
in the past with unhelpful results, such as the antigliadin
antibody (AGA) test, which is pretty much abandoned now. The
next blood test developed looks for antiendomysium (or
antiendomysial) antibodies (EMA). While the EMA test is
superior to the antigliadin test, the interpretation of the
test is operator-dependent and prone to errors. The newest
blood test looks for IgA antibodies to the enzyme
transglutaminase (TG). TG is an intracellular enzyme that binds
gliadin and starts to process it in a way that starts the
autoimmune sequence in CD. As the TG test has turned out to be
a very sensitive and specific screening test for CD, it has
become the favored screening test, especially for children and
adults who have no symptoms of CD. Note that all these tests
are measuring IgA levels of the antibodies. One problem is that
IgA deficiency may occur in people with CD, and therefore the
IgA markers for CD may not show up. That would classify as a
"false negative." For that reason, every time a
person has blood tests for CD, the doctor should also test for
total IgA levels.
Recent research has found that 97 to 98% of
all cases of CD are found in people with certain genetic
markers. These genetic markers are called HLA ("human
leukocyte antigen") markers. There are two markers that
are associated with CD: HLA-DQ2 and HLA-DQ8. In cases where CD
is suspected and there is an IgA deficiency, these markers can
be looked for instead to determine if a small bowel biopsy is
warranted. Children with DS and CD also have the same markers.
Interestingly, the genes for the HLA markers are on the
chromosome 6, so the connection to chromosome 21 still needs to
be discovered.
It's important to note that infection from
Giardia, a microscopic parasite found worldwide, can mimic CD.
Diagnosis of this infection is done by special tests on the
stools.
Treatment is both simple and difficult: a
gluten-free diet. All wheat, barley and rye products are off
limits. Currently, it is recommended that oats be also
eliminated from the diet at the beginning. They can be replaced
in the diet as soon as the patient is doing better. In most
cases, the symptoms of CD resolves in 2 weeks! The older the
child, the longer it takes to come under control. CD is a
lifelong disease; symptoms may from time to time subside to the
point of the CD appearing to be gone, but the person must
continue on the diet to avoid illness. The person may need
vitamin supplementation to complete the diet.
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Constipation is usually defined as the
presence of hard or thick, pasty stools which cause discomfort
as they are passed. In severe cases, the child has an inability
to pass the hard stool on his/her own.
The direct cause of constipation is not
enough water in the stool. This occurs because of the diet not
having enough water-retaining elements (fiber) or because the
stool is kept in the rectum too long, allowing the colon to
reabsorb more water than usual.
In children with Down syndrome, two factors
exist to make constipation more likely: low muscle tone and
decreased motor activity. Both of these make the colon more
likely to retain stool for longer periods, leading to loss of
water from the stool.
If left untreated, constipation can lead to
(1) rectal fissures: tears in the rectum leading to bright red
blood on the surface of the stool and on the toilet paper, but
not mixed in with the stool; (2) impaction; (3) stretching of
the rectum leading to the loss of the sensation of the need to
have a bowel movement. This last problem can further lead to
the weakening of the rectal muscles (sphincters) and cause the
child to have bowel movement accidents (in medicalese,
"encopresis").
The usual treatment of constipation is
dietary: increasing fiber, fruits and vegetables. In bottle-fed
babies, the introduction of a stool softener is used, such as
corn syrup (Karo), malt barley extract (Maltsupex) or lactulose
(Diphulac). Lactulose is also used in children and adults. All
of these soften the stool by adding water to the stool. Another
way of adding dietary fiber is through products such as
Metamucil, Citrucel, or fiber wafers. Increasing the amount of
fluids the child drinks is helpful; and in older children,
decreasing the amount of constipating foods (milk products,
bananas, white rice) may also help.
For babies who are having a hard time
passing a stool, the use of glycerin can be helpful. These can
be found as solid suppositories or in liquid form (Babylax),
and are useful as occasional measure. For severe constipation,
your doctor will usually recommend a medicated suppository or
enema; please do not use these without consulting your doctor
first. Likewise, avoid other laxatives unless your doctor
specifically recommends them.
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Apnea (literally, "without
breath") is the term used when someone stops breathing for
very short periods of time, usually 10 to 20 seconds. It's
termed "obstructive" when respiratory efforts
continue, such as movements of the chest. It's termed
"central" when all respiratory effort stops. There is
also a mixed version. In children, sleep apnea is almost always
obstructive. During the apneic episode, the child will have
decreased oxygenation of the blood.
Symptoms of Obstructive Sleep Apnea (OSA)
are: snoring, restless/disturbed sleep, frequent partial or
total wakenings and daytime mouth breathing. Some children with
OSA have odd sleep positions, often with their neck bent
backwards, or even in a sitting position. Some children with
OSA sweat profusely during sleep. In adults, there is an
association of obesity, but that's not a common association in
children. Some children will have daytime grumpiness or
sleepiness, but it's not common. Some children may have noisy
swallowing as well.
Children with Down syndrome (DS) are
certainly at risk for OSA. In 1991, one study showed 45% had
OSA. This can be caused by several different factors present in
DS: the flattened midface, narrowed nasopharyngeal area, low
tone of the muscles of the upper airway and enlarged adenoids
and/or tonsils.
Why is this important? Well, first, there's
the obvious problem of the child not getting enough quality
sleep and the behavioral effects that brings. Second, I've
mentioned above that during sleep apnea, the oxygenation of the
blood decreases. It has been shown that in children with DS and
heart disease this low oxygenation causes an increase in the
blood pressure in the lungs as the body tries to get more
oxygen. This "pulmonary hypertension" can cause the
right side of the heart to become enlarged and other cardiac
complications can follow. The incidence of death due to OSA is
unknown.
If you're unsure if your child has OSA, the
way to test is through a sleep study, also called
polysomnography. This test is performed overnight in a hospital
(though some doctors will do "nap somnography") and
consists of continuous monitoring of the oxygen in the blood,
as well as monitoring chest wall movements (to assess
respiratory efforts) and the flow of air through the nose. Some
doctors also measure carbon dioxide in the blood or exhaled
air. This is usually performed by otolaryngologists or
neonatologists.
The treatment of OSA is usually removal of
adenoids and/or tonsils. Various studies have been done on
children with DS, and this appears to relieve OSA in most
cases. However, it has been estimated that 30 to 40% of
children with DS and OSA develop recurrent or persistant OSA
even after removal of the tonsils and adenoids. There are
several different reasons for this, including a large tongue,
blockage of the airway by movement of the tongue during sleep,
low muscle tone of the area of the airway just below the
throat, and regrowth of the adenoids. When there is some
concern regarding the effectiveness of the initial surgery,
then post-surgical polysomnography is needed to document the
OSA. Some centers are now using a type of MRI that takes
sequential pictures of the airway while the child or adult is
asleep to evaluate possible causes for persistant or recurrent
OSA, and basing further surgery on those results; this is
described in more detail in this study.
In adults and children in whom surgical
treatment has failed or was not indicated, one therapy is
"continuous positive airway pressure," or CPAP. This
is administered by a nasal mask or tube during sleep. The
tube/mask administers air with an amount of pressure designed
to keep the airway open.
One final note about adenotonsillectomies
in children with DS: this should not be considered day surgery.
Studies have shown that after T&A's, children with DS have
longer periods of decreased oxygenation and a slower time to
recovery.
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Congenital heart disease (the presence of a
structural heart defect at birth) occurs in 40 - 50% of
children with Down syndrome and cardiac abnormalities are
probably the most common malformations seen in trisomy 21. The
most common heart defect (about 2/3) is called an endocardial
cushion defect or atrioventricular canal defect. In its
complete form there is a hole (defect) in the wall (septum)
between the pumping chambers (ventricles)and a hole in the wall
between the receiving chambers (atria) of the heart. In
addition, rather than two valves inside the heart between the
receiving and pumping chambers, there is a large single valve.
This defect requires surgical repair, which involves closing
both holes and creating two valves out of the one large valve.
This surgery is usually done in the first
few months of life. Less common defects are the presence of a
hole between just the ventricles (VSD) or between just the
atria (ASD) and depending on the size of the hole, these
defects may or may not require surgery. The holes do not get
bigger with growth of the child and can spontaneously get
smaller thus not requiring surgery. Children with Down syndrome
may also be born with cyanotic congenital heart disease of be a
"blue baby". Most commonly this is a defect called
Tretralogy of Fallot, which is a complex structural problem
that requires surgical repair and does not spontaneously fix
itself. Timing of the surgery is dependent on how cyanotic
(blue) the baby is.
Because congenital heart disease is so
common, it is recommended that all children with Down syndrome
have a full Pediatric Cardiology evaluation by 2 months of age.
Also, it is well recognized that children with Down syndrome
are at risk for developing damage in their lung arteries at an
early age if they have a heart defect. There appears to be a
number of reasons for this increased risk but it is critical to
recognize the defect and do the repair early since the severe
damage can be irreversible and progressive even after surgery.
The timing of surgery is dependent on how the child is doing,
however, as a rule it is done by 6 months of age and virtually
always by one year of age.
Children with Down syndrome without
anatomic heart disease also are at risk for the development of
pulmonary hypertension, which is high blood pressure in the
lung arteries. Usually when we think of blood pressure it is
the pressure in the systemic arteries and is measured most
commonly with a blood pressure cuff on your arm. The pulmonary
artery pressure can sometimes be estimated by echocardiography
but the only way to measure it directly is by placing a
catheter into the lung artery during a heart catherization. If
there is significant pulmonary hypertension, it places an
increased work on the right ventricle, which can be detected on
an electrocardiogram or echocardiogram. Again, thee appear to
be a number of reasons for pulmonary hypertension in these
children but one of the most significant is upper airway
obstruction, especially during sleep.
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Down Syndrome
of Louisville
4604 Bardstown Road
Louisville, KY 40218
Phone: (502) 495-5088
Fax: (502) 495-503
