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°