2019 ASAP Conference 

Craniocervical Instability - Summary

Video: 2019 ASAP Conference: Craniocervical Instability by P Bolognese


CCI – Craniocervical Instability.

CCJ – Craniocervical Junction

CXA – Clivioaxial Angle

GO – Grabb Oakes

RO – Retroflexed Odontoid

EDS – Ehlers-Danlos Syndrome

*Kids are different in relation to CCI as they are still growing and can’t be lumped in with adults. So, all discussion below is in reference to adults.

This is a summary of the video attached, these are not the opinions of the writer nor do they state they either agree or disagree with the points made.

Morphometrics (Radiological Measurements):

Measures used for the CCJ are old (50+yrs) and are historically based on measured used ot asses trauma to the CCJ.

There are 24 measures used for the CCJ and while not all are needed for CCI you can’t boil CCI down to one measure (The CXA is the most common measure stated on social media in relation to CCI).

First-Tier Measures: CXA and Grabb-Oakes/pBc2 are used for screening in relation to CCI

2nd Tier measurements – Harris – BDI and BAI

Those 4 measures are the best to screen for CCI as a whole.

If both CXA and GO are messed up that’s positive screening for CCI, but when only one is abnormal? Opinions are mixed in relation to that problem.

Hard and Soft Values:

Ligaments are an integral part for EDS patients, so should be considered as part of the measures that investigate CCI in conjunction with bone.

Measurements in radiological Imaging is not simple and no one is perfect. One can get multiple opinions on the same image between different doctors.

MRI images the better-quality ones are the best as MRI’s using flex/ext are usually done in an open MRI which only uses a 0.6T strength MRI (Compared to most places offering 3T and above). Get the best quality images you can.

For every measurement used on your images there is a threshold used on what’s normal and what is abnormal. There is also a grey area between normal and abnormal and no consensus on how to treat them.

GO/PBc2: Originally used to assess RO and predicting who would need surgery. Using the measurement in respect to this failed but was later picked up by the CCI community and re-worked.

GO measure shows the Mass Effect exerted on the brainstem by the tip of the odontoid and ligaments. (Example of mass effect: your sibling person sitting on you).

<6mm = normal

>8.5mm = abnormal pathological.

CXA: Measures stress deformity on the brain – the stretch of the brainstem by the odontoid. >145 normal

<135 pathological

Anything between is grey areas

The CCJ more in three directions: horizontal, vertical and rotational. Some people can have instability in 1, 2 or 3 of these directions or a mix.

CXA and GO/pBC2 are measures of horizontal instability ONLY

Basion Dens Intervals (BDI) used for vertical instability measurement and this is an important measure

AGAIN: Performing morphometrics/measures on MRI’s is not easy (don’t do it yourself) 3 different doctors will give you 3 different measures for the same MRI. Moving things slightly when you don’t have anatomical training in measures can cause huge variations in measures.

Important section @ 32:20 mins

Abnormal measures do not equal instability. These measurements show you that you are HYPERMOBILE.

Hypermobility does not equal instability.

All the US gymnastic team will be hypermobile and have abnormal measures, but you wouldn’t fuse them.

Saying abnormal measurements means that you need a fusion is very dangerous position to take in isolation.

So when is it instability?

Hypermobile measures + symptoms that you can link to CCI.

How do you demonstrate the symptoms you hare having are connected to the CCJ?

Provocative tests – used to see if there is a link between a symptom and the disorder (think like when you enter a new hour and play with light switches to find which switch works on which light).

Many people DON’T need fusion and should check out conservative measures FIRST such as the Kevin Muldowney protocol with your physio – best maintenance for your EDS body (https://www.muldowneypt.com/ehlers-danlos-syndrome-information/)

Surgical management

Bad radiological measurements/morphometrics does not mean surgery is needed. Surgery is considered when there is morphometrics positive for CCI AND

  • Severe debilitating symptoms that are positively linked to CCI
  • Failed conservative treatment
  • Positive provocative tests

Some surgeries will be urgent, others will be elective and you need to discuss with your surgeon.


Transoral Odontoidectomy – Rarely used now as it’s an extreme surgery.

Traditional fusion is done with a bar plate (12-15cm) and screws in the supraocciput

Screws are also put in at least the C1, C2 vertebrae as they are part of the CCJ. Fusion may extend further as needed.

Surgery is not just about putting the hardware in as the metal bars will bend overtime. Need to be combined with bone over the top to cement the fusion.

CCI and Complex Chiari – The name complex Chiari was proposed by a Utah doctor. Previously called Chiari+ as it was Chiari + RO.

Problems with complex Chiari complex and fusion is both have competing surgical interests as the fusion limits space the Chiari decompression increases space over the same area. Both surgeries are fighting each other’s needs. Questions still exist on whether to do both surgeries together or staged? EDS patients also can have poor bone metabolism so can make it hard to get the bone to fuse.

A newer technique for fusion came about in 2009 – Condylar screw fixation. Screws placed at the base of the skull on a bony area called the condyles. This results in a shorter fusion length. It can also address the space issues of complex Chiari and CCI fusion.

Pros and cons of the condylar vs Craniocervical Fusion which is still a gold standard. Neither is “better” and its more based on patients’ needs which one to use.

Link: https://www.youtube.com/watch?v=zUdwvBDnWpE&feature=youtu.be&fbclid=IwAR2J09ZjoiCEh_d_zGBxiSODdoFKIYaxOIgR_KBVLY8jE88UTWYq9nCSqd4