Thank you very much,
@bombsh3ll and
@Silencio, for posting the details of your reports from Dr Gilete and Dr Bolognese, it's very useful for me to see, to help organize the questionnaire I am working on.
I didn't actually think there was anything wrong with my CXA but note it is 129 in flexion. Does the above refer to the neutral position only?
I am not entirely sure; I've assumed the pathological reference range for these measurements refer to the neutral head position (except in the case of the translational BAI, where it is the change in the BAI from the flexion to extension head positions that you measure). But in
this 2019 paper by Dr Henderson says:
The CXA measurements were taken from the flexion image, when it was available.
Henderson also mentions the CXA in
this video at 8:17, but does not indicate whether the angle is to be measured in neutral or flexion positions.
Yes, 135 and lower refers to neutral. Jen gathered some info on mepedia:
https://www.me-pedia.org/wiki/Craniocervical_instability#Measurements
Are you certain of this, because I could not find any sources which explicitly say that it is in the neutral position that these reference ranges for the various measurements apply. Although Dr Bolognese mainly uses supine MRIs for his diagnosis without flexion and extension views, so in his case it's only the neutral position he examines (however he says he does sometimes order upright MRIs with flexion and extension views).
Here are the reference ranges for the various measurements:
Sources:
here and
here.
Clivo-axial angle (CXA)
An angle of
145º to
160º is normal. Borderline is
136º to
144º. An angle of
135º or less is considered pathological and indicates a possible mechanical deformity of the brainstem and upper spinal cord. Source: Dr Bolognese in
this video at 14:28.
Grabb-Oakes (B-pC2)
Less that
6 mm is normal (see
this video at 49:30). A distance of
9 mm or greater is pathological and indicates brainstem compression. (Some use
8.5 mm as the threshold for pathological — see
this video at 49:30)
Basion-axis interval (BAI)
Greater than
12 mm is pathological and indicates craniocervical instability (see
this video at 10:34, and the
Harris study).
Basion-dens interval (BDI)
Greater than
12 mm is pathological and indicates craniocervical instability (see
this video at 10:34, and the
Harris study).
Translational BAI
Less than
1 mm change between flexion and extension is normal; greater than
2 mm is pathological and indicates craniocervical instability. Dr Henderson stipulates the translational BAI must be greater than
4 mm in order to be a candidate for fusion surgery.
Chamberlain's line
If the tip of the dens (also called the odontoid peg) is more than
3 mm above Chamberlain's line, it indicates basilar invagination (vertical craniocervical instability), causing brainstem compression as the dens impinges on the brainstem or upper cervical spine. Source:
here. See also
this video of Dr Gilete at 1:16.
Chiari malformation
Chiari I malformation may be diagnosed if the cerebellar tonsils protrude more than
3 to 5 mm below the opening at the bottom of the skull (the foramen magnum). Source:
here. In one study, all patients with greater than 12 mm of protrusion were symptomatic for Chiari, whereas approximately 30% of those whose protrusion measured between 5 and 10 mm remained without symptoms. Source:
here.
Dr Paolo Bolognese in
this 2018 video at 54:46 says CXA and Grabb-Oakes are more sensitive to horizontal craniocervical instability, whereas the basion-dens interval (BDI) is more sensitive to vertical craniocervical instability.
Dr Bolognese in
the 2018 video at 1:12:44 says some patients have pathological measurements indicating CCI, but show no symptoms. No surgery is advised for these patients.
Regarding the CXA and Grabb-Oakes: in the case when one is positive and the other negative, Dr Bolognese and Dr Henderson have different opinions as to which takes precedence. Henderson thinks the CXA should take precedence, Bolognese thinks the Grabb-Oakes should take precedence. See
the 2018 video at 41:48.
@bombsh3ll, am I right in thinking that both Dr Gilete and Dr Bolognese found that you were negative for CCI?
@Silencio, not that I know much about this, but it looks like it might be your translational BAI of 8.6 mm that resulted in your diagnosis of CCI, as this is higher than the > 2 mm reference range threshold.