Continued from Issue #12
Orthopedic Disorder and Atlanto-Axial Instability (AAI)
Ligamentous laxity is responsible for a number of orthopedic difficulties in individuals with DS. Interestingly, congenital hip dislocation is not commonly encountered. Hip dislocation is more often seen in the older child and the adolescent. Chronic patellar dislocation can lead to gait disturbances in the adolescent. Atlanto-axial instability is a term used to describe increased mobility of the cervical spine at the level of the first and second vertebrae. This condition is found in approximately 14% of individuals with Down syndrome. The majority of individuals with atlantoaxial instability are asymptomatic, but approximately 10% of these individuals with AAI (representing 1% of individuals with Down syndrome) have symptoms, which occur when the spinal cord is compressed by the excessive mobility of the two vertebrae which form the atlantoaxial joint. Symptoms of spinal cord compression may include neck pain, unusual posturing of the head and neck (torticollis), change in gait, loss of upper body strength, abnormal neurological reflexes, and change in bowel/bladder functioning.
Routine radiographic screening for atlanto-axial instability of individuals with Down syndrome is controversial. In a recent review, the American Academy of Pediatrics Committee on Sports Medicine and Fitness concluded that screening radiographs are of "potential but unproven value" in detecting individuals at risk from sports injury. Close clinical scrutiny and further study of this issue was recommended. However, these studies continue to be required for participation in Special Olympics and community programs in horseback riding, gymnastics, etc.
Currently, DSMIG (Down Syndrome Medical Interest Group) recommends screening individuals between 3 and 5 years of age with lateral cervical radiographs in the neutral, flexed, and extended positions. The space between the posterior segment of the anterior arch of C1 and the anterior segment of the odontoid process of C2 should be measured. Measurements of less than 5mm are normal; 5 to 7 mm indicates instability, and greater than 7mm is grossly abnormal. The cervical canal width should also be measured. The interpretation of these studies should be performed by a radiologist experienced in this area. Individuals with Down syndrome who have not been screened may need to be evaluated prior to surgical procedures, especially those involving manipulation of the neck. These children should be managed cautiously by anesthesiology staff. The studies should be repeated, as needed, for participation in Special Olympics.
Children with borderline findings or abnormal films should be evaluated with a careful neurological examination to rule out spinal cord compression. Neuro-imaging (CT Scan or MRI) is probably indicated. Significant changes in a child's neurological status would necessitate evaluation and possible treatment (i.e., spinal fusion). Asymptomatic children with instability (5 to 7 mm) should be managed conservatively, with restriction only in those activities which posse a risk for cervical spine injury. Contact sports, such as football, wrestling, rugby, boxing, and recreational activities such as trampolining, gymnastics (tumbling), and diving, which require significant flexion of the neck, would best be avoided. It is unnecessary to restrict all activities.
We are no longer recommending repeat screenings at fixed intervals, inasmuch as the value of this procedure has not yet been confirmed in preventing injury. We strongly recommend careful neurological examination of the individual with Down syndrome, immediate attention to symptoms indicating neck or spinal cord problems (see above), and vigilance by ENT physicians and anesthesiologist during surgical procedures which may hyperextend the neck.
The editor understands that the Special Olympics Medical Advisory Committee is involved in clarifying the problematic issue of detection and prevention of spinal cord injuries.
Since infants with DS may have difficulty with feeding from birth, keep in mind that many centers have professionals (such as occupational therapists, speech pathologist, feeding nurse specialists, etc.) who can provide expertise in this area. Some centers involve the occupational therapist or feeding specialist on a routine basis, while others assess the child's oral-motor function and refer as needed. In general, physical and occupational therapy services are included in most early intervention programs for infants, where positioning, feeding, and motor strengthening exercises are some of the services available.
In addition to congenital abnormalities, such as duodenal atresia and imperforate anus, which are readily identifiable, babies with Down syndrome are more likely to have partial upper GI obstruction (duodenal web), tracheo-esophageal fistula, and pyloric stenosis. Chronic constipation occurs frequently, and the serious conditions in the differential diagnosis include hypo-thyroidism, and Hirschsprung disease. Failure to pass meconium in the first 24 hours suggests the possibility of Hirschsprung disease. Significant constipation which is refractory to dietary management warrants further investigation, such as referral to a pediatric gastroenterologist for further studies (barium enema, rectal biopsy).
Gastroesophageal reflux (GER) occurs in infants with DS, as it does in the typical population. In addition to spitting up and vomiting, some children have respiratory symptoms, such as cough, stridor, wheezing and pneumonia. BER must be part of the differential diagnosis for these conditions, and appropriate treatment given.
Celiac disease occurs in from 7 to 16% of children with DS, though many of these studies are from European sources. Individuals with DS are felt to be predisposed to this condition because of the known increased incidence of autoimmune disorders. Screening is best accomplished using IgA antiendomysium antibodies, following up positive results with a villous biopsy. Symptoms usually resolve following institution of a gluten-free diet.
A medical genetics consultation should be encouraged, in order to explain the genetic basis and risk of recurrence of DS. Such consultation may be considered optional for children with Trisomy 21. However, in cases of translocation, the parents should be evaluated to determine whether none of them is a balanced carrier of the translocation, thereby increasing the likelihood that subsequent children may have Down syndrome. This service should also be made available to individuals with DS, when appropriate.
Prenatal screening and testing technologies continue to evolve. Proposed methods include separating fetal cells from the maternal circulation, and use of multiple serum markers and nuchal thickness as measured by ultrasonography.
Coming Next Issue: More Guidelines for Individuals with Down syndrome
This article first appeared in issue #13 of Down Syndrome Amongst Us