AAI - Atlantoaxial Instability

Sorry for the blurry picture but here's evidence of K's fascination with all things doctor...........most 5 year olds probably wouldn't notice this poster.  See how K is pointing  out the details to me? She had to read most of it too lol!

Atlantoaxial instability is a separation between the C1 & C2 vertebrae.  In the last few days I've been doing quite a bit of research on this subject & in most cases I read that a separation of up to 5mm is considered normal "for kids with T21" although in some reports I've read up to 4.5 mm.  For kids with T21 is in quotes in the above sentence because I hate when doctors clarify things that way - there are many times when doctors decide that things are "normal" for kids with T21 which they would treat in typical kids - thyroid problems are a common example of this.  Anyways, back on topic again..........

Occipital-atlanto instability is also not uncommon in kids with T21 & occurs between the occipital lobe & C1 vertebrae. The incidence of these conditions is anywhere from 10 to 30% & very few of the people affected have any symptoms. Here is a quote from the NDSS page on AAI:

""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..."

Yet I can think of a couple of kids who weren't even 3 when they were affected.  Off the top of my head, there was a little boy whose mom used to post on the BBC DS forum who went in for a T&A surgery but was X-rayed first & ended up having surgery for AAI instead.  Another is little Rhiannon who was about 3 months older than K. She passed away due to undetected AAI. So why aren't we testing?  It occurs in 10 to 30% & most have no symptoms? I understand that an X-ray is not a perfect test for diagnosing AAI but in my opinion a less than perfect test is better than ignoring the potential danger.......& this is potentially very dangerous.  

We've been considering having a screening X-ray done  for K since she was almost 3 years old. It used to be recommended at around that age.  We choose to wait for 2 reasons: By age 5 the child's bones have calcified more providing a better X-ray & because we only wanted to have to do it once so that we were exposing her to less radiation from the X-ray especially because the thyroid cannot be protected during this X-ray.

In the meantime, the guidelines for this diagnostic test changed both in the US as well as here in Canada.  Although I printed the Canadian guidelines off for myself as well as an extra copy for K's pediatrician, D r. S, last summer, I can't seem to find the link, but here are the American (AAP) guidelines which I'm sure are quite similar. They no longer recommend a diagnostic X-ray. Again, I completely disagree with this. 

Here is the section on AAI & AOI taken directly from the Official Journal of American Pediatrics:

"

Atlantoaxial Instability

Discuss with parents, at least biennially, the importance of cervical spine-positioning precautions for protection of the cervical spine during any anesthetic, surgical, or radiographic procedure. Perform careful history and physical examination with attention to myelopathic signs and symptoms at every well-child visit or when symptoms possibly attributable to spinal cord impingement are reported. Parents should also be instructed to contact their physician for new onset of symptoms of change in gait or use of arms or hands, change in bowel or bladder function, neck pain, stiff neck, head tilt, torticollis, how the child positions his or her head, change in general function, or weakness.

The Asymptomatic Child

Children with Down syndrome are at increased risk of atlantoaxial subluxation. However, the child must be 3 years of age to have adequate vertebral mineralization and epiphyseal development for accurate radiographic evaluation of the cervical spine.⁵² Plain radiographs do not predict well which children are at increased risk of developing spine problems, and normal radiographs do not provide assurance that a child will not develop spine problems later.^53,54 For these reasons, routine radiologic evaluation of the cervical spine in asymptomatic children is not recommended. Current evidence does not support performing routine screening radiographs for assessment of potential atlantoaxial instability in asymptomatic children.^55,–,64 Parents should be advised that participation in some sports, including contact sports such as football and soccer and gymnastics (usually at older ages), places children at increased risk of spinal cord injury⁶⁵ and that trampoline use should be avoided by all children with or without Down syndrome younger than 6 years and by older children unless under direct professional supervision.^66,67 Special Olympics has specific screening requirements for participation in some sports.⁶⁸

The Symptomatic Child

Any child who has significant neck pain, radicular pain, weakness, spasticity or change in tone, gait difficulties, hyperreflexia, change in bowel or bladder function, or other signs or symptoms of myelopathy must undergo plain cervical spine radiography in the neutral position.^55,65 If significant radiographic abnormalities are present in the neutral position, no further radiographs should be taken and the patient should be referred as quickly as possible to a pediatric neurosurgeon or pediatric orthopedic surgeon with expertise in evaluating and treating atlantoaxial instability. If no significant radiographic abnormalities are present, flexion and extension radiographs may be obtained before the patient is promptly referred.<sup>23,62,63


As I said, I completely disagree with these recommendations so this spring I asked K's pediatrician to have this done. As per the guidelines, he didn't feel it was necessary but ordered it anyways because he respects my need to have certain extra testing done for my peace of mind. 

 We actually went to have the X-ray done a couple of months ago but when we arrived I realized that the orders were just for a regular side view of K's neck.  I had researched in the past & even spoke with an expert at a US Shriner's hospital who said flexion & extension views were necessary to diagnose AAI. I refused to allow the side view so it was back to the pediatrician to inform him about which types of X-rays are necessary.  Thankfully he not only understands that I research all of my daughter's health concerns but actually recommends parents be very informed so he happily accepted my recommendation & changed the orders to include flexion & extension views.  If you are getting this done for your child make sure they do the proper views.

K has been fascinated by anything to do with doctors lately so she was quite willing to cooperate for the X-ray.  She happily sat on the stool & carefully followed the directions for each X-ray view, flexing her neck so her chin was tucked in & extending it back when asked.

I checked that test off my list & went on my way fully expecting to never hear a thing about it. Within a few days I received a phone call.  Of course they wouldn't share any details over the phone but they did admit that K has AAI.  They didn't actually have any appointments left until early December but the kind hearted nurse understood that I have no patience when it comes to the health of my kids & squeezed us in for an appointment 2 days later.  

Of course I spent the any time I could during that next 2 days at my computer & here are a few links that I found very helpful.

The Garden of Eagan is a blog written by a mom whose son has had  successful surgery for AAI. Her youngest also has this condition & is being monitored.  She is very knowledgeable & has been wonderful at answering my questions.

Life With My Special K's is another blog by a mom whose daughter had spinal fusion surgery. This is a very informative post.

I really like Paul Doney's AAI page on his Super Down Syndrome site. Not only is it full of information, but I found the diagrams made it easier to understand & it has links to some studies & other info on the bottom of the page. 


During K's appointment I found out that K does have AAI & the gap is 4.7mm.  As I said earlier, according to my research some feel that that a separation of up to 5mm is considered normal " although in other reports I've read up to 4.5 mm. At 4.7 K falls right in the middle of that area.  Upon receiving the X-ray report K's pediatrician had phoned a neurologist at our local children's hospital.  The neurologist feels up to 5mm is normal for kids with T21 so he said K should have no restrictions on her activities.  I questioned Dr S on activities such as skiing as we did just buy K a new, larger set of skis last week & he replied that the neurologist said no restrictions. I admit that I'm a little nervous about the gap in K's neck being within that grey area & so close to being at a level that would require restrictions on her activities. On the other hand, the gap rarely widens unless there is a trauma to the neck.  The other thing to consider is that the X-ray is not always a reliable test.  My plan for now is to still be a little more cautious like we've always been.  K won't be allowed to do summersaults & we'll keep using a harness when skiing until we are confident that she can ski in control.  I will be requesting a followup X-ray at some point down the road.</sup>