ATLANTO-AXIAL INSTABILITY
AMONG PEOPLE WITH DOWN'S SYNDROME
by Dr Jennifer Dennis, Medical Adviser to the Down's Syndrome Association
Antlanto-axial instability
In people with Down's syndrome the ligaments which normally hold the joints
stable can be very slack. This can lead to an unusually wide range of movement
at some joints, much greater than in the general population. As well as
affecting the ordinary limb joints, this can affect the stability of one of the
joints in the neck, the atlanto-axial joint. This joint is the highest joint in
the spinal column and it lies just at the base of the skull. There is movement
at this joint whenever the head is nodded or shaken. When the atlas and axis
vertebrae are firmly bound to each other, both move together when the neck
bends forward. However, when the ligaments binding the joint are slack, the
atlas moves forward but fails to carry the axis with it.
In some people with Down's syndrome, in addition to a slack ligament, the
actual bones of the atlanto-axial joint may be poorly developed. Theoretically
these differences could make the joint more likely to dislocate than in people
without Down's syndrome.
The spinal cord which carries all the nerve messages from the brain to the
rest of the body passes very close to the atlanto-axial joint. Bruising of the
spinal cord can happen to anyone, with or without Down's syndrome. This can
either happen suddenly, as a result of a sudden shift within the joint, or more
gradually because of a day-to-day pressure on the spinal cord as the neck
moves.
Because of the changes within the joint in some people with Down's syndrome,
the following questions arise:
- are people with Down's syndrome more at risk than the rest of the
population for whiplash type injuries and possibly some sporting injuries (such
injuries could lead to paralysis)?
- are people with Down's syndrome more at risk than the rest of the
population for difficulties which can arise as a result of chronic pressure on
the neck?
- if there is an increased risk of either of the above is it possible to
predict which people with Down's syndrome are most likely to be affected?
- is it possible to do anything to prevent sudden injuries, or the more
slowly developing long-term effects of atlanto-axial instability?
The answers to these questions are undecided, which is why doctors may vary
in the advice they give.
Sporting activities
It is clear that very few sporting injuries have ever been recorded in
people with Down's syndrome which could have been caused by atlanto-axial
instability. In fact the injuries recorded would have been just as likely to
occur in an ordinary person as a result of a similar fall or accident. Sports
such as trampolining, diving, and boxing, do carry an element of risk for
anyone, not just for people with Down's syndrome. People can accidentally fall
onto their head in many sports.
People with Down's syndrome may be less at risk because many are less
vigorous in their activities than their peers without Down's syndrome. On the
other hand they may be more at risk in some activities because they tend to be
less well co-ordinated. These two considerations may well balance each other
out.
Doctors are often asked whether simple forward rolls or supervised bouncing
up and down on a mini-trampoline in a nursery school are particularly dangerous
for children with Down's syndrome. The answer is that there is no good evidence
that they should be so. The same applies to the early stages of horse-riding.
At a more advanced stage in all these pursuits a greater element of risk is
inevitable for everyone, whether with or without Down's syndrome.
Precautions
There are reports of whip-lash injuries in people with Down's syndrome
following road traffic accidents, possibly more than in the general population.
It seems sensible therefore to recommend that head-rests are always in place
when a person with Down's syndrome is travelling. Similarly, after a road
traffic accident, it is important to alert helpers to the fact that a person
with Down's syndrome is more likely to have sustained a neck injury than
another person.
Another point to be aware of is that doctors will need to take special care
when giving the sort of anaesthetic which involves passing a tube down the
windpipe, because in achieving this the neck position can be strained and joint
dislocation can occur.
Both sudden neck dislocation and the more slowly developing effects of
chronic atlanto-axial instability certainly do occur in a few people with
Down's syndrome, and it is important to be on the lookout for early signs which
may indicate that a problem is developing.
Compression
If there is constant pressure on the spinal cord in the neck because the
atlanto-axial joint is either chronically displaced or keeps dislocating, then
there may be some neck pain and/or deterioration of some motor skills. There
are some symptoms which should alert you that some compression may be
occurring.
Look out for:
- pain at a spot near the hard bump behind the ear
- a stiff neck which does not get better quickly
- an alteration in the way a person walks, so that he/she appears less good
on his/her feet
- deterioration in a person's ability to manipulate things with his/her hands
- incontinence developing in a person who has previously had no problems
If any of these occur the person should be seen by a doctor.
Treatment
A doctor suspecting that atlanto-axial instability may be present and
causing problems in a person with Down's syndrome will probably refer that
person to either an orthopaedic surgeon or a neuro-surgeon. If instability or
dislocation is confirmed and is thought to be causing problems, an operation
can be done to stabilise the upper part of the spinal column. The operation is
delicate and not without risk, particularly in younger children, but it can be
100% successful in treating the problem.
Children with dislocation have also been successfully treated by traction,
which eases the pressure in the neck and allows the joint to get back in place,
followed by immobilisation of the neck until the joint has firmed up again.
X-ray investigation
The question which has caused the greatest confusion with regard to
atlanto-axial instability is whether or not people should have neck x-rays to
find out if the joint is unstable.
We now know that neck x-rays taken in the routine manner followed in most
x-ray departments are unlikely to be reliable in identifying instability. Some
people who initially appear to have instability as shown by a neck x-ray can
show no evidence of instability if x-rayed again one week later. Equally people
whose neck x-ray appears entirely normal can show apparent evidence of x-ray
instability one week later. On the basis of these findings there appears to be
no useful information gained by carrying out such an x-ray.
X-rays can be taken in research conditions where results are known to be
consistent from week to week. Even then, if instability is shown, we do not
know if it is these people who are most at risk of sustaining a sudden
dislocation-type injury at some time in the future. In fact we have evidence of
the reverse, namely of people with no x-rav evidence of instability who
subsequently sustain a neck dislocation.
Department of Health guidelines
Guidelines about atlanto-axial instability in people with Down's syndrome
were drawn up in 1986 by a standing medical advisory committee for the then
Department of Health and Social Security (DHSS), now the Department of Health
(DoH), and their Chief Medical Officer. These were issued to all schools,
social services departments, and doctors. They were drawn up because some
people with Down's syndrome had been banned from taking part in the Special
Olympics.
The guidelines were in general reassuring, and the advice was against
routine x-ray screening for all people with Down's syndrome. It was recommended
however that x-rays should be carried out in those intending to participate in
vigorous sporting activity, because at that time it was thought that such
x-rays could show definitely if a person had an instability.
These guidelines have not yet been revised, so some doctors and local
authorities consider that for legal reasons they must insist that people with
Down's syndrome have neck x-rays before taking part in vigorous sporting
activities. Some schools and LEAs have even been restrictive about letting
children with Down's syndrome take part in even quite ordinary sporting
activities. This is probably because of misunderstanding about the actual
wording of the guidelines.
Recommendations
The situation remains difficult for all concerned - parents, schools, other
carers and doctors.
Doctors can give very different advice as to what should or should not be
done. Some insist that all children with Down's syndrome should have neck
x-rays before starting school and advise those with apparent x-ray instability
against taking part in activities such as forward rolls or trampolining, as
well as any more vigorous activities. This is a more extreme recommendation
than that put forward by the DHSS and there is little scientific evidence to
support this course of action.
My local colleagues and I no longer feel that we can justify routine neck
x-rays. When we look at the x-rays we do not know if we would get the same
picture if we took a second film. Even if we were sure that a particular
picture was reliable we could not be 100 per cent certain of giving the right
advice and/or reassurance for that individual. We hope that the Department of
Health may be persuaded to look again at this issue in the light of more recent
evidence.
Restrictions
Many schools, colleges, and LEAs feel that they may be at risk of legal
action should injury occur, unless they interpret and follow the DoH guidelines
rigorously. The DSA has recently had a considerable number of enquiries from
parents and teachers who wish a particular child or student to continue with
sporting activities despite these being restricted by the establishment
concerned.
If you find yourself in this position you can sign a disclaimer. This should
say that you have considered the information available and understand about the
possible risks involved, but would nevertheless like your child (or yourself if
you are over 18) to take part in the currently restricted activity. You will
need to discuss the wording of this with the school or college. Our information
is that most are willing to follow this course of action.
You may of course consider that it is in your child's best interests to have
some limitations imposed on sporting activities, and be quite happy to go along
with the restrictions set by the establishment.
A personal view
My own view is that there are two issues at the present time which are more
important than whether or not we should be taking x-rays. We have to try to
increase awareness among parents, carers, and professionals, of some possible
risk situations where non-restrictive precautions can be taken to reduce the
chance of neck injury. We also need to increase awareness of the symptoms of
atlanto-axial dislocation and of the early signs of chronic pressure on the
spinal cord. If we succeed in this, people are more likely to consult a doctor
before any permanent damage ensues. Both of these issues have been discussed
here.
Life for everyone is not without risk. It is for the individual to decide
what risks are acceptable for their children or for themselves. We all have to
compromise in our day-to-day lives as we balance freedom to take part in, and
enjoy, life's activities against the risk of possible injury.
For further information, contact either:
Down's Syndrome Association
155 Mitcham Road
London
SW17 9PG
 020-8682 4001
 020-8682 4012
or:
Down's Syndrome Association - Scotland
158-160 Balgreen Road
Edinburgh
EH11 3AU
0131-313 4225
|
