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Medical Information

  • Antioaxial Instability

    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), in-coordination 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.

  • Celiac Disease and DS

    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 contaminated 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 œsensitive 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.

  • Constipation

    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.

  • Obstructive Sleep Apnea

    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.

  • Congenital Heart Disease

    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 or 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.