Angles which should be measured


Angles which are very important for the diagnosis of CCI and should be measured by your neuroradiologist, radiologist or neurosurgeon.

Bulls Angle

Bulls Angle

Bulls Angle

Draw a line between posterior and anterior arch of C1 → angle between this line and hard palate.

Pathological: > 13 degrees

 

Powers Ratio

Power's Ratio

Power’s Ratio

Distance between basion and posterior arch of atlas divided by distance between opisthion and anterior arch of atlas.

Pathological: > 1

 

Basion dens interval (BDI)

BDI

BDI

Distance between basion and tip of dens.

Pathological: > 12 mm

 

Basion axial interval (BAI)

BAI

BAI

Basion to posterior line of axis.

Pathological: > 12 mm

 

Harris Measurment

Harris measurement

Harris measurement

BDI + BAI

Pathological: > 12 mm

Additional, the BAI should be measured in flexion and extension. If the value varies by more than 1-2 mm this means that the head is sliding backwards and forward on the cervical spine.

 

MC Gregors line for basilar invagination

McGregor's Line

McGregor’s Line

Draw a line from the upper surface of the posterior edge of the hard palate to the posterior lowest point of the occiput. If the tip of the dens is more than 4,5 mm above the McGregors line then a basilar invagination is likely.

 

Grabb Oaks Line brain stem compression

Grabb Oaks Line

Grabb Oaks Line

To diagnose brain stem compression.

Draw a line on middle sagital MRI scans from the lowest point of the clivus to the lowest posterior point of the axis corpus. Measure in a right angle from this line to the beginning of the spinal canal.

Pathological: > 8 mm

 

 

Wackenheim Line

Wackenheims Line

Wackenheims Line

Angle between clivus line and dural canal. This line should go through the dens or be tangential to it.

 

Clivo Axial Angle (CXA)

CXA

CXA

Draw a line along the clivus and a second one down on the posterior side of the axis.

Normal: between 150 degrees in flexion and 180 degrees in extension.
< 150 degrees typical for basiooccipitale hypoplasia, risk of myelon compression

Wiesmann M, Linn J, Brückmann H, editors. Atlas Klinische Neuroradiologie: Wirbelsäule und Spinalkanal. Springer-Verlag; 2013 Dec 30.

 

Definitions :

Basion:
Is the anterior center of the foramen magnum

Opisthion :
Is the posterior center of the foramen magnum

Clivus :
Right at the junction of the sphenoid bone and the anterior part of the basilar occipital bone a sloping process arises, the clivus.

 

http://radref.org/ref.php?cat=27&subcat=33

 

Angular instability:

Angular instability

Angular instability

Pathological: > 11 mm

 

Horizontal displacement:

Horizontale Displacement

Horizontale Displacement

Pathological: > 3,5 mm

 

Atlantoaxial instability:

Pathological: space between dens and C1 > 2-3 mm

 

„Normal“ imaging in the symptomatic patient.
CSF/MUSC Half Day Symposium 2014 Dr. Myles Koby:

http://csfinfo.org/videos/physician-lecture-videos/csf-lectures-archive/csf-musc-symposium-myles-koby/

 

Sources:

 

Verhaagen J, McDonald III JW, editors. Spinal Cord Injury: Handbook of Clinical Neurology Series. Newnes; 2012 Dec 31.

Panjabi MM, White III AA. Basic biomechanics of the spine. Neurosurgery. 1980 Jul 1;7(1):76-93.

Benzel EC, Connolly PJ, editors. The cervical spine. Lippincott Williams & Wilkins; 2012 Aug 29.

DePalma AF. Spinal fusion: science and technique. Cotler JM, Cotler HB, editors. Springer Science & Business Media; 2012 Dec 6.

 

ADLS measurement

The atlantodental lateral shift (ADLS) measurement is used to determine lateral displacement of the altas in comparison to the dens axis. Deviation between atlas and dens is measured on lateral x-ray images with open mouth in flexion and extension, as well as AP images with open mouth in lateral beding.

Taniguchi D, D Tokunaga, Hase H, Mikami Y, Hojo T, Ikeda T, Oda R, R Takatori, Imai K, Kida Y, Otakara E. Evaluation of lateral instability of the atlanto-axial joint in rheumatoid arthritis using dynamic open- mouth view radiographs. Clinical rheumatology. 2008 Jul 1; 27 (7): 851-7.

Fujiwara S, D Tokunaga, Oda R, Toyama S, Imai K, Doi A, Kubo T. Dynamic close-mouth view radiograph method for the diagnosis of lateral dynamic instability of the atlantoaxial joint. Clinical imaging. 2010 Oct 31; 34 (5): 375-8.