by Michael J. Goldberg, MD
Michael J. Goldberg, MD, is Henry H. Banks professor and chairman, department of orthopaedics, Tufts University School of Medicine.
The question posed for this Point of View column was: should children with Down syndrome with Cl-C2 subluxation be allowed to compete in the Special Olympics? My personal recommendation is yes they should be allowed to compete.
Structural abnormalities in the upper cervical spine are frequently observed in people with Down syndrome. Although they may be a source of disability or death in both children and young adults, that is clearly the exception. Some 15 percent of children with Down syndrome have an atlanto-dens interval of 5 mm or more. The reported incidence varies somewhat, based on whether the epidemiologic survey was a population of people with Down syndrome living in the community or in an institution, and various authors selected parameters for normal motion of the upper cervical spine seemingly arbitrarily.
For some children with Down syndrome, Cl-C2 instability is more than just a roentgenographic curiosity; they develop signs and symptoms of cervical myelopathy. However, this is a decidedly small number. More than 90 percent of people with Down syndrome who have an atlanto-dens interval of 5 mm or more will have no neurologic symptoms whatsoever. Those few who do develop cord compression usually do so before age 10, have significant ligamentous laxity, and are more often girls. More importantly, these patients have had readily detectable physical signs and symptoms for several weeks or months prior to any catastrophic Cl-C2 dislocation. Indeed, acute subluxation is exceedingly rare; the onset of myelopathy is usually chronic and insidious. Symptoms and signs of Cl-C2 instability may be vague and considering the difficulty communicating with a retarded population, diagnosis has often been delayed for months, even years.
The roentgenographic screening of thousands of people with Down syndrome resulted in the identification of many other cervical spine abnormalities, some of which are even more common than an increased atlanto-dens interval. These additional anomalies include occiput-Cl instability; odontoid dysplasia; hypoplasia of the posterior arch of Cl; spondylolysis and spondylolisthesis of mid-cervical vertebrae; and precocious arthritis.
Despite a wealth of observations, the natural history of cervical spine instability is unknown and controlled long-term longitudinal studies are lacking. The impression of most observers is that the vast majority of people with Down syndrome and cervical spine instability remain entirely asymptomatic, and the abnormal atlanto-dens interval does not change over time. Instability developing in children who initially had no instability has been suggested, but this awaits documentation. Data are lacking to support the notion that an increased Cl-C2 interval predisposes to progressive subluxation and myelopathy. Indeed, it has been suggested by some that a physical examination with careful attention to neurologic signs is better than a cervical spine radiograph when screening for participation in the Special Olympics, especially when the number of technically inadequate X-rays are taken into account.
Atlanto-dens instability in persons with Down syndrome was reported in the scientific literature more than 20 years ago, but only recently was there a frenzy of administrative activity on behalf of the Special Olympics Inc. There was a rush towards implementing screening programs and guidelines. Many guidelines seem not to be based on a convincing scientific rational and many were very restrictive regarding sports participation. It was unclear whether screening programs were designed to safeguard sports participants or the sponsoring organizations. The dilemmas these screening programs created included:
It seems reasonable that people with Down syndrome should undergo roentgenographic evaluation of their cervical spine. This is best done at age 3 or 4 after walking has begun, when there is sufficient ossification of the vertebrae, and the patient is relatively cooperative.
If the initial film is abnormal, it is reasonable to obtain follow-up radiographs from time to time although there is weak evidence to support this recommendation. If the initial film is normal, most opinion holds that it is not necessary to repeat cervical spine screening unless doing so is a local committee requirement for participation in the Special Olympics. An annual cervical spine screening is not justified by the scientific literature.
People with Down syndrome should have access to routine health care and part of that must include a careful neurologic examination.
If the person with Down syndrome has an increased atlanto-dens interval but has an entirely normal physical examination, then restricting all sports seem unnecessarily harsh. It is prudent, however, to avoid sports that require stressful weight-bearing on the head such as tumbling, gymnastics, and perhaps, diving. Limiting all sports activities such as running, swimming, bowling, softball, dance, and track and field events is not justified by either the scientific literature nor by the occasional anecdote of a youngster getting into trouble. Indeed, the overall benefits of sports participation for the social integration of people with Down syndrome, for cardiovascular conditioning, and as a means of weight control far outweigh the risk of damage to the cervical spine.
Goldberg, MJ. Spine instability and the Special Olympics. Clinics in Sports Medicine, 12:507-515, 1993.