Increased flexibility of joints, called ligamentous laxity, is common among individuals with Down syndrome. Atlanto-axial instability (AAI) is the medical term used when referring to an increased flexibility or mobility of the 1st and 2nd cervical vertebrae (bones of the neck). The vertebrae protects the spinal cord so if there is instability of this joint, the spinal cord could be at risk for injury.
Here are a few articles on AAI for further reading:
Atlantoaxial Instability in Down Syndrome
AAI information from the NDSC
Atlantoaxial Instability Among People with Down Syndrome
An overview of the development of infants with Down syndrome (0-5 years) - Health
Reasons for Assessment
Matthew turned 3 this month. Generally, the first screening with an x-ray is done between ages 3 and 5, when the bones are more likely to have developed enough to show clearly. However, if Matthew was showing symptoms of spinal cord damage (which he's not), then his pediatrician would have recommended the x-ray sooner.
Another reason for getting this done now instead of a little later is his upcoming surgery. He will be undergoing a tonsillectomy, adenoidectomy and bilateral myringotomy. Translation: getting his tonsils removed, adenoid removed and ear tubes put in both ears. This surgery will require a general anesthesia and a breathing tube placed down the windpipe. There are rare, but possible, cases of neck injury such as joint dislocation from placement of the breathing tube. (Writing about this makes me more anxious about his upcoming surgery). The findings of the x-ray is good information for his ENT who will be performing the surgery.
Direct quote from the x-ray report:
The study includes flexion, extension and neutral positioning in the lateral projection, demonstrating the distance between the odontoid projection, and the anterior arch of C1 to measure between 2.7 and 3.9 nodes, felt to be within normal limits.
The study is otherwise unremarkable. No fracture or subluxation is seen.
According to our pediatrician and what I've read, anything above 4.5 millimeters (mm) or 5mm suggests AAI.
What does this mean for Matthew?
It simply means that he doesn't have particular restrictions on activities that put extra strain on the neck. We can explore the possibility of signing up for therapeutic horse riding lessons. He doesn't necessarily have to avoid activities like jumping on a trampoline and tumbling. For now.
He'll need another x-ray in his teens or when he goes through a growth spurt. I hope they don't find AAI then.