Radiological assessment of CVJ in children. 2nd European Society for Pediatric Neurosurgery (ESPN) Hands-on Workshop on Craniovertebral Junction Surgery, Lyon, France

1. What to ask, what to search for…
felice.d’arco@gosh.nhs.uk

2. Objectives
 Radiological techniques
 Radiological anatomy of
CVJ (…a lot of variant
and pitfalls)
 Measurements (which are
really “Good”?)
 Atlanto-Occipital
Dislocation (“The Bad”)
 Atlanto-axial rotatory
fixation (“the Ugly”)
 Cases (genetic
conditions)

3. What’s the
difference?

4. • CT (static – dynamic – 3D - MPR)
optimally defines the osseous structures
Radiation exposure

5. MRI
• MRI (static - dynamic)
ideal for evaluation of soft tissues, neural structures, and ligaments / bone edema
T1
T2 – with
fat
saturation T2
T1 mdc
Patient compliance!

6. 1. Anatomy
Paediatric spine evolves rapidly....
Pediatric Spine (<10-12yo): different anatomy
and different mechanism of injury

7. Normal anatomy
“the cervicocranium is the region extending from the basi-
occiput to the 2nd vertebral interspace”(Harris. Radiology 2001)
At 3-6 years another ossification center appears (os odontoideum) that fuses around 12

8. Normal anatomy
“the cervicocranium is the region extending from the basi-
occiput to the 2nd vertebral interspace”(Harris. Radiology 2001)
At 3-6 years another ossification center appears (os odontoideum) that fuses around 12

9. Basioccipital bone
Exoccipitals bones
Supraoccipital bone (derived
from cartilage)
Interparietal bone (derived from
membrane)
Mendosal Suture

10. Ossification timing
5m 3y 7y
As general rule: Normal synchondrosis smooth and regular, are seen in predictable
locations, and have sclerotic lines.
1m 3-6y 12y

11. Karwacki et al. AJNR

12. Variants and Pitfalls

13. Normal measurements
“Standard for radiological assessment of the spine shifted
from X-Ray to MDCT”(Gale et al. 2005; Rojas et al. 2006)
So....please ASK for CT and USE MEASUREMENTS!
XR MR
But...discrepancies between normal ranges accepted for
X plain radiographs and MDCT

14. Measurements and Normal Values
BDI distance from the most inferior portion of the
basion to the closest point of the superior
aspect of the dens. V.N. < 10.5 mm (vs 12 mm on
radiographs)
ADI: line from anterior arch of C1 to the
most anterior aspect of the dens. V.N: < 2.6 mm
(vs 3 mm radiographs)
Powers Ratio: A (tip of the basion - the
spinolaminar line) / B (tip of the opisthion -midpoint
anterior arch of C1.). V.N: < 1 and > 0.7 mm
detection of anterior atlanto-occipital
dissociation

15. Measurements and Normal Values
AOI: line perpendicular to the articular surfaces
of the occipital condyle and the lateral mass of
C1. v.n: < 2.5 mm
BAI: Posterior axial line along the posterior
cortex of the body of C2. The BAI is the distance
between the basion and this line. V.N. < 12 mm
(?)

16. ‘’Instability occurs each time the anatomical relationships between the articular
components are altered or have the propensity of becoming abnormal under the
influence of certain solicitations” Ganhem et al. 2008
2.CVJ INSTABILITY
• Atlanto-occipital dislocation
(C0-C1 instability)
• Atlanto-axial rotatory
subluxation/fixation
(C1-C2 instability)
• Sub-axial subluxation

17. Case 1
• 8 yo boy
• motor vehicle collision
(backseat)
• Cardio-respiratory arrest
Warning !!
Atlanto-Occipital Dislocation

18. • Malalignment betweeen the cranium and
the spine
• Extremely rare
• Rupture of ligaments
• AOI strongest indicator of atlanto-occipital
dislocation (use also Power and BDI)
• Classification may be biased by patient
positioning
• CT: diagnosis; MRI: prognostication
Atlanto-Occipital Dislocation: Teaching points
Traynelis classification
Beez et al 2016
Pang et al 2007

19. Case 2
8 year old female; Hx: 2 week severe throat infection on abx; Ex: Persistent
Left sided painful torticollis.
What is the name of this position?

20. “Cock- robin” position Head rotated to left
Atlanto-axial rotatory fixation

21. Type 1: simple rotatory
displacement without an
anterior shift. Transverse
lig intact !
Type 2: rotatory
displacement with an
anterior shift < 5 mm or
less.
Transverse lig. disrupted !
Type 3: rotatory
displacement with an
anterior shift > 5 mm or
less.
Transverse and alar lig.
disrupted !
Type 4: rotatory
displacement with a
posterior shift.
Odontoid hypoplasia
Fielding and Hawkin classification scheme
for atlantoaxial rotatory fixation (AARF)
Violent impact ! What if less violent?

22. Atlantoaxial Rotatory Fixation: CT diagnosis (Pang et al.)
C1 angle C2 angle C1 angle -C2 angle
For the first 23 degrees of head turning,
C2 remains immobile, and C1 moves
independently of C2 (C1=C1-C2).
For the first 24-65 degrees of head
turning, C2 and C1 moves but
different velocity (relationship
between the angles is not linear)
From 65 degrees of head turning,
C2 and C1 moves together (plateau)
with difference angle of 43

23. C1 angle (C1 degrees)
denoted the head position
C1–C2 angle (C1–C2
degrees) represented
Plotting C1 vs C1-C2 angle
we now know the
physiological range!
Linear relationship
nonlinear relationship
Plateau

24. 3 patients as example
Oc.-C1 always stable!
0 degrees Oc, C1 and C2
are in line
Range movements are the
same on both sides

25. Atlantoaxial Rotatory Fixation: To recap
 The pathologically fixed state can be
indistinguishable from normal rotation in a static
radiographic film
 Complete lock is rare…  look for abnormal C1-C2
interactions rather than no motion!
 Mean C1 location when C2 begins to turn is 23
degrees
 Max separation C1/C2 is 43 degrees and
happens when rotation of C1 is 65 degrees
 CT protocol: 1) presenting position, 2) nose up
(center), 3) opposite side as much as is tolerated
 5 Groups of AARF

26. Group 1: minimal change of C1-C2 angle at maximal
correction (fixation)
P_ head cranked on the opposite
side but still the angle between C1
and C2 remains the same

27. Group 2: the separation between C1 and C2 narrowed
with correction, but C1 never could cross C2 (marked
stickness but no lock)
P_ head cranked on
the opposite,the angle
between C1 and C2 is
less but still positive
(no crossing between
C1 and C2)

28. Group 3: the separation between C1 and C2 narrowed
with correction, C1 crosses C2 but in abnormal position
(moderate pathological stickiness)
When C1 crosses C2 is not in
neutral position (nose pointing
upward)
You need to look to the neutral
position and to draw the curve in
this case !

29. Template in emergency room

30. Case 3
• 10 year old female, Tri 21
• Hx: cervical pain, torticollis, recent decline in balance
• Ex: High cervical myelopathy, poor balance, reducible torticollis
• CT +/- MR examination
Findings: Os odeontoideum with anterior subluxation of C1 on
C2. The spinal canal is narrowed and there is evidence of cord
compression with signal change within the cord

31. Teaching points
 DS patients: abnormal joint anatomy,
ligament laxity, bony abnormalities such as
os odontoideum.
 Atlantoaxial instability affects 10–20% of
individuals with DS.
 Os odontoideum: associated with
syndromes characterised by ligaments laxity
(Morquio, Down, Achndoplasia, Larson).
Traumatic aetiology.

32. Case 4
• 9 year old female
• Hx: Headache, facial pain, poor hearing,
swallowing difficulties
• Ex: trigeminal neuralgia, sensorineural
hearing loss, bulbar dysfunction
• MR examination
Diagnosis: Osteogensis imperfect, basilar impression with brainstem
compression and Chiari 1 deformity

33. Teaching points
 OI patients:Pathology in the craniocervical junction is a
serious complication of osteogenesis imperfecta (OI)
 Basilar invagination, basilar impression, and platybasia.
 B. Invagination: protrusion vertebrae in the foramen
magnum (normal bone)
 B. Impression: similar but due to softening of bones in
skull base
 They are often coexistent and are due to softened bones
Dr. M. Skalski

34. Case 5
• 2 year old male
• Hx: recent
regression in motor
skill
• Ex: mild high
cervical myelopathy,
short stature,
kyphoscoliosis,
mandibular
prominence
• MR examination

35. Teaching points
 MPS IV Morquio: dwarfism, join laxity,
kyphoscoliosis
 Platyspondyly
 Hypoplasia odontoid peg
 Os odontoideum
 Peripheral muscoloskeletal manifestation
penyakitlangkaindonesia.org

36. Take Home Messages
 Knowing the anatomy is half of
the job!
 Measurements are out there: use
them!
 Atlanto-axial rotatory subluxation
 Pang method, is less
complicated than it looks like and
pays back!
 Genetic causes of CVJ instability

37. Villa Rufolo – Ravello (Italy)
Aknwoledgement
s:
Dr. G. Morana
Mr. D. Thompson
Dr. K. Mankad