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Pediatric CCJ Companion
Nadja Kadom, Gilbert Vezina, Raymond Sze
C-spine measurements
Trauma
Basilar Invagination
Platybasia
Assess the C-Spine/skull baseTrauma:
• Alignment
• Soft tissue swelling
• Occiput-C1 dissociation
• C1-C2 instability
Basilar Invagination
• Chamberlain
• McGregor
Platybasia
• Standard
• Modified
Trauma
Prevertebral/Retropharyngeal Soft Tissues
• False thickening: flexion, end of expiration
Flexed Extended
Prevertebral/Retropharyngeal Soft Tissues
Normal thickness:
• < 7 mm anterior to C2 and < 5 mm anterior to C3/C4
• or less than half the diameter of the vertebral bodies
Prevertebral/Retropharyngeal Soft Tissues
Loss of physiological mucosal step off ~C4/5 is ABNORMAL!
Step-off ~ C4-6 Lost step-off
Alignment
Soft Tissue Swelling
In children:
Retropharyngeal tissues should NOT exceed1/2 to 2/3 vertebral body AP diameter
Evaluate Occiput-C1 dissociation:Suggestion: Get C0-C2 CT scan
Landmarks not seen on x-ray, get limited CT
CT
Basion-Dens-Interval (BDI): 8.37 (pediatric normal < 12.5 mm)Basion-Axial Line-Interval (BAI): 5.56 (adult normal < 12 mm)
Other methods
• Power ratio
• Lee X
Power Ratio
A = the anterior tubercle of the atlas. B.= the basion. C = the spinolaminar line of the atlas. O = the opisthionThe value BC/AO should be less than 1.
BC/AO = 30.21/39.59 < 1normal
C1-C2 instability
Atlanto-dens interval (ADI) and posterior atlanto-dens interval (PADI)
ADI = 3.24 mm (normal < 5 mm)PADI = 21.92 (abnormal < 13 mm)
Occiput-C1 Pathology
• Axial dislocation (dislocation in the axial plane, anterior or posterior “listhesis” of occiput versus C1, best seen on sagittal images)
• Sagittal dislocation (dislocation in the sagittal plane, increased height of space between occipital condyles and C1 articulation, seen on coronal and sagittal images)
Occipital Condyle-C1 Interval(CCI)
1. CCI physiologically narrow normal pediatric mean is 1.28 mm, normal range 0.25-2.5 mm2. The left and right OC1 joints are normally highly symmetrical
Right Left
Example of CCI enlargement
Example of asymmetry
Wackenheim line
• Assess antlanto-occipital dissociation
• Line along the posterior border of the clivus should inferiorly touch the odontoid tangentially
Examples
Normal Posterior dislocation
Rotatory subluxation C1-C2
• 4 types
• Assess the facet joints, look for:
=> displaced facets on sagittal views
=> visualization of both articular surfaces in one axial image
Type I: simple rotatory displacement; < 3 mm with an intact transverse ligament.
Type II: anterior displacement of C1 on C2 of 3-5 mm (one lateral mass serving as a pivot point) + deficiency of the transverse ligament.
Type III: injuries involve > 5 mm of anterior displacement.
Type IV: injuries involve the posterior displacement of C1 on C2.
Both Type III and IV are highly unstable injuries.
Basilar Invagination
Basilar Invagination
Definition
• The tip of the dens projects more than 5 mm above Chamberlain's line
• Or the tip of the dens is >7 mm above McGregor's line
Chamberlain’s line
• line joining the hard palate to the posterior lip of the foramen magnum
McGregor’s line
• the back of the hard palate to the lowest point of the occipital squama
PlatybasiaStandard technique: • measuring the angle formed by two lines: 1st line: nasion to center of the pituitary fossa 2nd line: anterior border of foramen magnum with
center of the pituitary fossa (= tip of clivus to center of pituitary)
Normal:• Adult: 129° +/- 6° • Pediatric: 127° +/- 5°
Koenigsberg RA, Vakil N, Hong TA, Htaik T, Faerber E, Maiorano T, Dua M, Faro S, Gonzales C. Evaluation of platybasia with MR imaging. AJNR Am J Neuroradiol. 2005 Jan;26(1):89-92.
Standard:
Pediatric: 127° +/- 5°
PlatybasiaModified technique: Uses different landmarks• measuring the angle formed by two lines: 1st line: extending across the anterior cranial fossa to the
tip to the dorsum sellae 2nd line: connecting with a line drawn along the posterior
margin of the clivus
Normal:• Adult: 117° +/- 6° • Pediatric: 114.4° +/- 5°
Modified:
Pediatric: 114.4° +/- 5°