CVJ is one of the most complex segment for radiologists,,,,, lets see it in an easy way

1. PRESENTER : DR.PRASHANT SARDA
MODERATOR: DR.MANOJ HAZARIKA

2. CRANIOVERTEBRAL JUNCTION
•The craniovertebral junction(CVJ) is a collective term that
refers to the occiput, atlas, axis, and supporting ligaments.
•It is a transition zone b/w a mobile cranium & relatively rigid
spinal column.
•It encloses the soft tissue structures of the cervico medullary
junction (medulla, spinal cord, and lower cranial nerves).

3. EMBRYOLOGY & DEVELOPMENT OF THE CVJ
Development of the cartilaginous cranium & the adjacent structures begins during the
early weeks of intrauterine life.
2ndGestational week:
Mesoderm cells condense in the midline to form notochordal process.
3rdGestational week:
-notochordal process invaginates in b/w ecto& endoderm to form notochord.
-dorsal ectoderm thickens to form neural groove which folds, fuses, & becomes neural
tube.
Between 3rd& 5thweek:
-part of mesoderm which lies on either side of notochord (Paraxial mesoderm) gives
rise to somites(Segmentation).
-total 42 somitesform at 4thweek.
-ventromedial portion of somite is k/a sclerotome which forms the vertebral bodies.
-each sclerotome differentiates into a cranial, loosely arranged portion and a caudal
compact portion by a fissure k/a “Fissure of von Ebner”(Re-segmentation).

4. Each sclerotome differentiates into a cranial, loosely arranged portion ( 1
) and a caudal compact portion (2).

5. Notochord disappears at the vertebral bodies, but persist as nucleus pulposus at disc.
Out of 4 occipital sclerotomes the first 2 form basiocciput, the 3rd Jugular
tubercles and the 4th (Proatlas) form parts of foramen magnum, atlas and
axis.
The “pro atlas” (1) is derived from the cranial portion of the embryonic fourth occipital
sclerotome. Its principal derivatives are the occipital condyles, the dorsal
cranial articular facets of the atlas, and the tip of the odontoid.
The “primitive atlas”
(2) is derived from the caudal portion of the fourth occipital and the cranial portion
of the first cervical sclerotomes. Its principal derivatives are the neural arches and
lateral masses of the atlas and the remainder of the odontoid process of the axis.
The “primitive axis” (3) is derived from the caudal portion of the first cervical
sclerotome and the cranial portion of the second. Its principal derivatives are
the body and neural arch of the axis and the C2-3 cervical disk.

6. OSSIFICATION CENTRES
OCCIPUT & BASIOCCIPUT:
2 occipital squamous portions –2 centres
Basiocciput(clivus) -1 centre
2 Jugular tubercles –2 centres
2 Occipital condyles–2 centres
ATLAS: ossifies from 3 centres
Each half of post. Arch with lateral mass unites at 3 –4 years.
Anterior arch unites with lateral mass at 6 –8 years.
AXIS: ossifies from 5 primary & 2 secondary centres.
2 Neural arches –2 centres appear at 7 –8 wk
Body of axis –1 centre appear at 4 –5 months
Body of dens –2 centres appear at 6 –7 months
4 pieces (at birth) unite at 3 –6 years
Tip of odontoid appears at 3 –6 years, unites with the body of odontoid at 12 years.

8. EMBRYOLOGY & DEVELOPMENT OF THE CVJ
ATLAS: no vertebral body & no IV disc.
-major portion formed by first spinal sclerotome.
-trasitional vertebra as centrum of sclerotome is separated to fuse with the axis body
forming the odontoid process.
-hypocentrum of 1st spinal sclerotome forms the anterior arch of the atlas.
-neural arch of the first spinal sclerotome forms the inferior portion of the posterior arch
of atlas
AXIS: develops from 2nd spinal sclerotome.
-hypocentrum of 2nd spinal sclerotome disappears during embryogenesis.
-centrum forms the body of the axis vertebra & neural arch develops into the facets &
the posterior arch of the axis.
-At birth odontoid base is separate from the body of axis by a cartilage which persists
until the age of 8, later the center gets ossified or may remain separate as Os-
odontoidium.
-The apical segment is not ossified until 3 years of age, at 12 years if fuses with
odontoid to form normal odontoid failure leads to Os terminale.
.

9. ANATOMY OF CVJ
(ARTICULAR)
Upper surfaces of C1 lateral
masses are concave which fit into
the ball & socket configuration.
4 synovial joints b/w atlas & axis
–
2 median –Pivot variety
2 lateral –Plane variety
Each joint has its own capsule &
synovial cavity.

10. ANATOMY OF CVJ(LIGAMENTOUS)
ATLANTO-OCCIPITAL LIGAMENTS:
A) Anterior Atlanto-occipital Membrane ----
about 2 cm wide
Ligament is continuous caudally with the anterior
A-A ligament & through it to the ALL of the spinal
column.
It acts as a tension band that stretches during
extension, serving as a secondary stabilizer against
this motion.
B) POSTERIOR ATLANTO-OCCIPITAL
MEMBRANE:
A less strong ligament containing no significant
elastic tissue.
Ligament invests itself on either side to form a
canal through which the vertebral artery,
accompanying veins, & the first cranial nerve pass.
C) LATERAL ATLANTO-OCCIPITAL
LIGAMENTS:
-ascending lig which reinforce the A-O joint
capsules.

11. ATLANTO AXIAL LIGAMENTS:
Anterior A-A ligament,
Posterior A-A ligament
Transverse ligament of the atlas:
-thick, strong & about 6mm in height.
-Caudal crus & Rostral crus(Fasciculi
longitudinales) fibres joined with
transverse ligament on its dorsal aspect
to form Cruciate ligament of atlas.
TAL effectively limits anterior
translation and flexion of the atlanto
axial joint.
An accessory band ventral to the
ascending crus attaching to the apex of
the odontoid process is termed Gerber’s
ligament.

13. A) TECTORIAL MEMBRANE:
•Dorsal to the cruciate ligament
•Attached to the dorsal surface of the C3
vertebra, axis body & to the body of dens.
•Rostral extension of the PLL of the
vertebral column.
•Essential for limiting flexion.
•The accessory bands of the ligament
passing to the lateral capsule of the A-A
joints --Arnold’s ligament
B) ALAR LIGAMENTS:
•2 strong cords that attach to the dorsal lateral
body of the dens .
•Extend laterally & rostrally.
•Ventral & cranial to the transverse lig. allow an
anterior shift of C1 from 3 to 5 mm.
•Limit the head –atlas rotatory movement on the
odontoid axis
•Strengthen the A-O capsule.
C) APICAL LIGAMENT:
.No mechanical significance.
AXIS –OCCIPITAL LIGAMENTS:

14. ANATOMY OF CVJ (MUSCLES)
Muscles have only a minor role related to CVJ stabilization & do not
limit the movements of the joints.
Their principal function is one of initiating & maintaining movement at
the CVJ.
Neural structures related to CVJ are –
Caudal portion of brainstem (Medulla)
Cerebellum
Fourth ventricle
Rostral part of spinal cord
Lower cranial & upper cervical nerves

15. ANATOMY OF CVJ (NEURAL)
In cerebellum, only the
tonsils, biventral lobules & the lower
part of the vermis(nodule, uvula &
pyramid) are related to CVJ.
Biventral lobule is located above the
lateral part of FM & the tonsils lie
above the posterior edge.
CRANIAL NERVES :
Lower four cranial N. are closely
related to CVJ.
9th & 10th cranial N arise from the
medulla in the groove b/w the inferior
olivary nucleus & the inferior
cerebellar peduncle.
The accessory N is the only
cranial N that passes through
the FM.

16. SPINAL NERVE ROOTS:
The C1, C2, and C3 nerves, distal to the ganglion, divide into dorsal and
ventral rami.
The first cervical nerve located just below the foramen magnum.
The dorsal rami divide into medial and lateral branches that supply the
skin and muscles of the posterior region of the neck.
.

17. ANATOMY OF CVJ (ARTERIAL)
The major arteries related to CVJ are
vertebral, postero inferior cerebellar arteries
(PICA), and the meningeal branches of the
vertebral, and external and internal carotid
arteries.
VERTEBRAL ARTERY arises from the upper
posterior part of the first segment of the
subclavian artery in the neck.
Each artery is divided into intradural and
extradural parts.
The branches arising from the vertebral
artery in the region of the FM are the posterior
spinal, anterior spinal, PICA, and anterior and
posterior meningeal arteries.
The PICA is the largest branch of the vertebral
artery

18. Brain stem arteries - anterior
view
1. Posterior cerebral artery
2. Superior cerebellar artery
3. Pontine branches of the
basilar artery
4. Anterior inferior cerebellar
artery
5. Internal auditory artery
6. Vertebral artery
7. Posterior inferior cerebellar
artery
8. Anterior spinal artery
9. Basilar artery
The tonsillo medullary PICA segment, which forms the caudal loop
related to the lower part of the tonsil, is most intimately related to the
foramen magnum.

19. ANATOMY OF CVJ (LYMPHATICS)
The lymphatic drainage of the O-A-A joints is primarily into the
retropharyngeal LN & then into the deep cervical chain.
These LN‟s also drain the nasopharynx & hence retrograde infection may
affect the synovial lining of the CVJ complex with resultant neck
stiffness & instability.
ANATOMY OF CVJ (VENOUS)
The venous structures in the region of the FM are divided into three
groups:
-Extradural veins(extraspinal & intraspinal part)
-Intradural(neural) veins, &
-Dural venous sinuses( superior petrosal, marginal & occipital)
􀂄 The three groups anastomose through bridging and emissary veins

20. KINETIC ANATOMY OF CVJ
􀂄 CVJ units are unique with respect to the rest of the spine in that they
do not bear weight through disks, but rather through synovial joints lined
with hyaline cartilage, thus exhibit significantly more movement than
any other spinal level.
􀂄 ROTATION : when movement occurs about an axis.
􀂄 TRANSLATION: when movement occurs along an axis.

21. ATLANTO-OCCIPITAL
JOINTS :
The C1 lateral masses contain the
occipital condyles in a cup-like
fashion.
Joint is biaxial having
movements only around the
transverse & A-P axes.
2 types of movement permitted are
forward or backward bending & a
slight lateral tilting motion to either
side.
These joints do not permit rotation.

22. ATLANTOAXIAL JOINTS :
􀂄 Consists of 2 lateral zygapophyseal & 2
median odontoid joints (pivot joint).
􀂄 Rotation of atlas occurs around the
odontoid.
􀂄 The superior facet of the axis is convex
& the inferior facet of the atlas is either
horizontal or slightly convex.
So the facets slide forward & backward
on each other with rotation.
􀂄 The A-A joints allow less flexion –
extension motion than rotation.
􀂄 There is greater movement with
extention (upto10deg ) than with flexion
(upto5deg).

23. 􀂄 Total rotation of the entire cervical
spine is upto 90deg & approx ½occurs at
the A-A joint.
􀂄 With a certain degree of anteflexion,
the tectorial membrane, cruciform &
Apical dens ligaments become slack & do
not check movement.
􀂄 Caput of dens then acts as a fulcrum,
resulting in tightening of the tectorial
membrane with consequent checking of
anteflexion(checking effect).
.

24. THE RADIOLOGIC IMAGING MODALITIES
 Conventional Radiography, including
standard and special projection
 Computed tomography (CT) – MP &
3D reconstructions
 Magnetic resonance imaging (MRI)

25. CERVICAL SPINE PROJECTIONS

26. RADIOLOGY OF CVJ
PLAIN FILM EXAMINATION:
A) LATERAL VIEW :
B) ANTERO-POSTERIOR (AP)-OPEN MOUTH VIEW :
Additionally detects dens anomalies & its lateral displacement.
C) OBLIQUE VIEWS:
Allows visualization of homolateral superior & inferior facets
as well as a small portion of the contralateral superior facet
Intervertebral neural canal for the 3rdcervical nerve also
evident

29. Cerebellar tonsils
medulla
Vertebral artery
basion

30. Medulla oblongata
basion
Anterior arch of atlas

31. Atlas (anterior arch)
Transverse lig. atlas
Dens of axis
Medulla oblongata
Vertebral artery
Atlas, posterior arch

32. Atlas, lateral mass
Transverse ligament
atlas
Transverse process and
foramen transversarium

33. Anterior longitudinal ligament
Apical ligament of dens
Tectorial membrane
Transverse ligament of atla
Anterior arch of atlas
Dens of axis (C2)

34. Clivus
Anterior atlanto-
occipital membrane
Atlas (lateral
mass)
Axis
Int carotid artery

35. Alar ligaments
Atlanto-axial jointAtlanto-occipital joint

36. CRANIOMETRY:
Craniometry of the CVJ uses a series of lines, planes
& angles to define the normal anatomic relationships
of the CVJ.
These measurements can be taken on plain X rays,
3D CT or on MRI.

37. THE CHAMBERLAIN’S LINE
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Chamberlain ‘s line
Palato-occipital line
Posterior pole of hard
palate to the Opisthion.
Tip of the dens usually
below and upto 3 mm
above this line.
Dens > 6mm in basilar
impression.
H O

38. THE MCGREGOR’S LINE
H
Low occiput
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Mc Gregor’s line
Basal line
MOST ACCURATE
Postero-superior margin
of Hard palate – most
inferior surface of
occipital bone.
Odontoid apex shouldn’t
lie above.
< 5mm
Superior lie of odontoid
indicates basilar
impression.(>5mm)
Low occiput

39. THE MCRAE’S LINE
B O
Mc Rae’s line
Formen magnum line
Anterior and posterior
ends of formen
magnum.
(Basion and Opisthion)
Inf margin of occiput
should lie at / below this
line. Tip of dens does
not exceed this line.
Perpendicular line along
odontoid intersects 1st
line in its anterior
quadrant.
Inf margin of occiput lies
superior – Basilar imp.
If sagittal diameter
< 20mm neurological
symptoms (+) (foramen
magnum stenosis)

40. CLIVUS-CANAL LINE
C
B
OC2
H
N
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Wackenhie’s line
Clivus canal line
Drawn along clivus into
cervical canal
Odontoid tip is ventral
and tangential to line
Odontoid transects the
line in basilar imp

41. BASILAR ANGLE
Mid sella
B
N
S
B
N
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Basilar angle
Welcker’s / Martin’s /
Spheno-BA
Nasion – Centre of the
sella – Basion.
Angle 1370
(123-1520)
>1520 Platybasia
(Base is elevated)
+/- Basilar impression
Modified MRI technique
This technique described by Koenigsbert et al yields a normal value range (95% C.I)
116° - 118° for adults and 113° - 115° for children.
Angle formed by :
line extending across the anterior cranial fossa to the tip to the dorsum sellae
line drawn along the posterior margin of the clivus

42. THE BOOGARD’S LINE
N
O
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Boogard ‘s Line Nasion to Opisthion Basion should lie below
this line
Altered in basilar
impression

43. BOOGARD’S ANGLE
Tuberculum sellaTuberculum sella
B o
N
s
C
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Boogard ‘s Angle Angle intersected by
1st line between Dorsum
sellae to Basion &
Mc Rae’s line.
119-1350
Average - 1220
> 1350
Basillar impression

44. METHOD OF BULL
C2
Chamberlain
Bull ‘s angle
Atlanto-palatine angle
Posterior Angle betn
1st line from Post tip of
hard palate to post
margin of foramen
magnum
2nd line betn ant & post
tubercles of atlas
Post angle <130 If odontoid is tilted
posteriorly or in case of
change of atlas position
The angle > 130

45. RANAWAT METHOD
C2
C1
Ranawat method Line joining center of the
anterior arch of C1 to
post ring & another line
along the axis of the
odontoid from the centre
of the pedicle of C2 to 1st
line
Normal distance between
C-1 and C-2 in
Men averages 17 mm
( 2 mm SD)
Women, 15 mm
( 2 mm SD).
A decrease in this
distance indicates
cephalad migration of
C-2.
C2
C1
C2
C1
PEDICLE

46. SCHMIDT – FISCHER ANGLE
(ATLANTO-OCCIPITAL JT AXIS ANGLE)
O
C2
AA JT
AO JT
C1 C1
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Schmidt – Fischer
Angle
Angle of axis of Atlanto-
Occipital joint
125 +/- 2 degrees Angle is wider in
condylar hypoplasia

47. CRANIO-VERTEBRAL ANGLE
ax
C
NAME & SYNONYMS OF
LINES
DEFINITION NORMAL MEASUREMENT IMPLICATIONS
Cranio vertebral angle Between clivus line and
post axial line
Flexion – 1500
Extension - 1800
<1500 Platybasia
cord compression
Basilar impression

48. •BDI less than 8.5 mm compared
with 12 mm on data from plain
radiographs.
• The Powers ratio demonstrated no
significant difference compared
with data obtained by plain
radiographs.
•An ADI less than 2 mm, compared
with 3 mm previously accepted.
•The AOI demonstrated 95% of the
population ranged between 0.5 mm
and 1.4 mm.
Midsagittal MDCT image of the
craniocervical junction demonstrates
the BDI as the distance from the most
inferior portion of the basion to the
closest point of the superior aspect of
the dens.
MDCT VS PLAIN RADIOGRAPHY
IN CRANIOMETRY…..

49. Midsagittal MDCT image of the craniocervical
junction demonstrates the Powers ratio, which is
calculated by dividing the distance between
the tip of the basion to the spinolaminar line
by the distance from the tip of the opisthion
to the midpoint of the posterior aspect of the
anterior arch of C1

50. MDCT image of the craniocervical junction
demonstrates the ADI, which is calculated
by drawing a line from the posterior aspect
of the anterior arch of C1 to the most
anterior aspect of the dens at the midpoint
of the thickness of the arch in
craniocaudal dimension

51. Sagittal MDCT image of the craniocervical
junction demonstrates the AOI, which is
calculated by drawing a line perpendicular
to the articular surfaces of the occipital
condyle and the lateral mass of C1. This
line is drawn at the center of the
articulation by correlating the sagittal and
coronal images.

52. (NORMAL VARIANTS & ANOMALIES)
THE OCCIPUT :
􀂄 The basiocciput forms the lower portion of the clivus.
􀂄 The upper portion of the clivusis formed by the basisphenoid, separated from the
basiocciput by the sphenooccipital synchondrosis.
􀂄 The age at which this synchondrosis fuses, ranges from “after the twelvth year”to
14-16 years for girls and 16-18.5 years for boys.
􀂄 Most occipital anomalies are associated with decreased skull base height and
basilar invagination.
CondylusTertius:
􀂄 When the hypochordal bow of the fourth occipital sclerotome(proatlas) persists or
when the proatlas fails to integrate, an ossified remnant may be present at the distal end
of the clivus, called the condylus tertius or third occipital condyle.
􀂄 This third condyle may form a joint or pseudojoint with the odontoid process or
with the anterior arch of the atlas and may lead to limitation in the range of motion of
the CVJ.
􀂄 There is an increased prevalence of osodontoideum associated with this abnormality

54. The Mach effect of the
overlying anterior arch of the
atlas may be mistaken for a
fracture of the apical region of
the odontoid on the open
mouth view.
Pseudo fracture of the odontoid
The Mach effect of the medial aspects of
the overlying incisors simulates avertical
defect in the odontoid on the open mouth
view. A bicornuate odontoid should be
considered.

55. The characteristic "V" shaped cleft in the
superior aspect of the odontoid and the
"diamond" shaped distal ossification centre
of pro atlas origin, are seen in the open
mouth view. This is a normal finding in
adolescent children.
Bicornuate odontoid…….

56. The radiolucent band separating the base of the
odontoid from the body of the axis in the
lateral projection is a normal finding in infants.
Sub dental synchondrosis……

57. The irregular fragments located inferior to
the Anterior arch of the atlas may be
mistaken for fracture fragments . The clear
cortical margins and characteristic location
help to differentiate this variant from a
fracture.
Accessory ossification centre for the anterior arch of
the atlas……

58. CondylarHypoplasia:
•In condylar hypoplasia, the
occipital condyles are
underdeveloped
•Have a flattened
appearance, leading to BI
Basiocciput Hypoplasia:
•It results in shortening of the clivus
and violation of the Chamberlain
line
•Virtually always associated with
basilar invagination.
•The Wackenheim clivus baseline is
usually normal,
• Clivus-canal angle is typically
decreased
• Bow-string deformity of the
cervicomedullary junction.

59. Sagittal T1 weighted (600/20) MRI shows
deformity of the pons and medulla due to
basilar impression. Note basiocciput
hypoplasia

60. Atlantooccipital Assimilation / Occipitalization of
Atlas:
•The failure of segmentation between the skull and
first cervical vertebra results in assimilation of the
atlas.
•The assimilation may be complete or partial.
•It invariably results in basilar invagination.
•Wackenheim clivus baseline may be normal, but
the clivus-canal angle may be decreased.
TOPOGRAPHIC FORMS (WACKENHEIM):
•Type I: Occipitalization(generally subtotal)
associated with BI.
•Type II: Occipitalization(generally subtotal)
associated with BI & fusion of axis & C3.
•Type III: Total or subtotal occipitalization with BI
& maldevelopment of the transverse ligament.

61. ATLAS :
􀂄 Most atlas anomalies, when isolated, produce no abnormal CVJ
relationships and are not associated with basilar invagination.
􀂄 The vast majority of anomalies consist of various arch clefts,
aplasias, and hypoplasias.
􀂄 Arch anomalies are frequently mistaken for fractures in the
evaluation of plain radiographs of patients with a history of cervical
spine trauma.

62. PONTICULUS POSTICUS / KIMMERLE’S
DEFORMITY :
􀂄 It is a bony ridge projecting posteriorly
from the articular edge of the atlas superior
articular facet.
􀂄 The bony projection unite with the
adjacent neural arch of the atlas to produce an
“ARCUATE CANAL”through which the
vertebral artery passes.
􀂄 This is due to ossification of a portion of
the oblique A-O ligament.
Posterior Arch Anomalies (MC atlas
anomaly) :
􀂄 Total or partial aplasia of the posterior
atlas arch is rare.
􀂄 Although absence of the posterior arch,
when isolated, is usually asymptomatic, but
may be associated with anterior atlantoaxial
subluxation.
Posterior arch hemiplasia

64. Split Atlas :
•In anterior arch rachischisis, the
anterior arch appears fat or
plump and rounded in
configuration, appearing to
„„overlap‟„ the odontoid process.
•The arch may have unsharp,
duplicated anterior margins.

65. Persistent OssiculumTerminale:
􀂄 Also called Bergman ossicle, results from
failure of fusion of the terminal ossicle to the
remainder of the odontoid process.
􀂄 The fusion typically is accomplished by 12
years of age.
􀂄 Bergman ossicle may be confused with a
type 1 odontoid fracture (avulsion of the
terminal ossicle), and absolute differentiation
between the two diagnoses may be difficult.
OdontoidAplasia:
Total aplasia of the odontoid process is extremely
rare.
A true aplasiais associated with an excavation
defect into the body of axis.
CONGENITAL ODONTOID ANOMALIES OR DYSPLASIAS

66. OS ODONTOIDEUM
•an independent osseous structure lying cephalad to the axis body in the location of
the odontoid process.
•The anterior arch of the atlas is rounded and hypertrophic but the posterior arch is
hypoplastic.
•Cruciate ligament incompetence and A-A instability are common
•The margins of the axis body, the os, and anterior arch are all well corticated.
•Odontoid fracture : flattened, sharp, uncorticated margin to the upper axis body.
Types –Orthotopic & Dystopic.
Instability is more common with dystopic type.

67. PLATYBASIA
BASILAR IMPRESSION
BASILAR INVAGINATION
These terms are not synonymous.

68. PLATYBASIA/Martin’s anamoly
Flattening of angle between the clivus and
the body of the sphenoid
C/F
PRIMARY
- Isolated or in conjunction with other
dysplasias like Achondroplasia,
Osteogenesis imperfecta
SECONDARY - Paget‟s disease / bone
softening / degenerative disease
Basilar angle > 152 (N=123-1520)
Craniovertebral = clivus-canal angle
becomes acute (<150 )
MC associated changes - Basilar
invagination, anomalies of
C1(occipitalisation)block vertebra,
Klippel-Feil syndrome.

69. •BASILAR INVAGINATION
•Floor of the skull is indented by the upper
cervical spine, & hence the tip of odontoid
is more cephalad protruding into the FM.
•Two types of basilar invagination:
primary invagination, and secondary
•Primary invagination can be associated
with occipito atlantal fusion, hypoplasia of
the atlas, a bifid posterior arch of the atlas,
odontoid anomalies.
•BI is associated with high incidence of
vertebral artery anomalies.
Chamberlain‟s line- tip of dens is >6mm above this line
Mc Gregor‟s line- tip of dens is > 5mm above this line
Mc Rae‟s line- tip of dens is above this line
Boogard‟s line- basion is above this line
Height index of Klaus < 30mm

70. .Topographic types of BI :
􀂄 Anterior BI : hypoplasiaof basilar process of the occipital bone.
􀂄 BI of the occipital condyles(Paramedian BI)
Condylar hypoplasia
􀂄 BI in the lateral condylar area.
􀂄 Posterior BI: posterior margin of the FM is invaginated.
􀂄 Unilateral BI.
􀂄 GeneralisedBI
usually occur in 2nd or 3rd decade.

71. BASILAR IMPRESSION
(SECONDARY BASILAR
INVAGINATION
•Basilar impression refers to secondary or
acquired forms of BI
• Due to softening of the bone
• Seen in conditions such as rickets,
hyperparathyroidism, osteogenesis
imperfecta, Paget disease, neurofibromatosis,
skeletal dysplasias, and RA & infection
producing bone destruction.

72. KLIPPEL FEIL SYNDROME
Described first by Klippel and Feilin 1912.
Etiology is unknown.
Due to failure of the normal segmentation of cervical somites during the third and
eighth weeks of gestation.
Classic triad of low posterior hair line, short neck and limited neck ROM found in
less than 50% of cases
The most consistent finding is limitation of neck motion.

73. Achondroplasia:
Genetically dominant disorder characterized by inhibition of
endochondral bone formation.
The base of the skull is affected but the membraneous convexity skull
bone grows normally.
This differential bone growth results in large calvarium on a small base.
A small FM with hypertrophic bone & a posterior dural shelf results in
compression of neural structures.
.

75. CRANIOVERTEBRAL JUNCTION ANOMALIES IN DOWN SYNDROME
􀂄 First described in 1965 by Tishler& Martel.
􀂄 Characterized by increased ligamentous laxity
and abnormal joint and bony anatomy, which
predispose to instability.
􀂄 The incidence of bony anomalies involving the
occipital condyle, C1 ring, and odontoidis also
increased in Down syndrome.

76. CHIARI MALFORMATION
􀂄 The Chiari malformations are a group of hindbrain herniation
syndromes initially described by Austrian pathologist Hans Chiari in
1891.

77. ARNOLD-CHIARI
MALFORMATION I
Present in adulthood ="cerebellar
tonsillar ectopia"
Herniation of cerebellar tonsils > 5mm
below a line connecting Basion with
Opisthion (= foramen magnum)
Causes:
• small posterior fossa,
•cerebellar overgrowth,
•disproportionate CSF absorption
Associated with:
1. Syringohydromyelia (30-56%)
2. Hydrocephalus (25-44%)
3. Malformation of skull base
NECT:
Effaced Posterior Fossa cisterns
"Crowded" Foramen Magnum
Lateral/3rd ventricles usually normal

78. Look for absent cisterna magna, posteriorly angled odontoid with
compressed brainstem, short posterior arch C1, short supra
occiput,syrinx

79. ARNOLD-CHIARI
MALFORMATION II
Des:
Most common and serious complex of
anomalies
HALLMARK is dysgenesis of
hindbrain with
(1)caudally displaced 4th ventricle
(2)caudally displaced brainstem
(3)tonsillar + vermian herniation through
foramen magnum
Associated with:
(a)spinal anomalies
(1)lumbar myelomeningocele
(2)syringohydromyelia
3)dysgenesis of corpus callosum
Radiography
Lucken shadel -Craniolacunia = Lacunar Skull
= mesenchymal dysplasia of calvarial
ossification
Absent / Hypoplastic posterior arch of C1
Myelography
Tethered cord
NECT
Small posterior fossa
Large, funnel-shaped foramen magnum
"Scalloped" petrous pyramid,
"notched" clivus
Absent falx cerebelli
Best diagnostic clue
Presence of Myelomeningocele
Small posterior fossa
Elongated, "straw-like" 4th ventricle
"Cascade" of tissue herniates through
foramen magnum behind upper cervical cord
• Vermis (nodulus)
• Choroid plexus of 4th V
• Medullary "spur"

80. ARNOLD-CHIARI
MALFORMATION III
• High cervical / occipital
meningoencephalocele + intracranial
Chiari 2
malformation
NECT
o Occipital squamo defect
Posterior spina bifida at the P1–P2 level
o Bony features of Chiari 2
Small posterior cranial fossa, scalloped
clivus, lacunar skull
MR Findings
TIWI
Sac contents
• Meninges, cerebellum, brain stem
• Cisterns, 4th ventricle, dural sinuses
o Hydrocephalus
T2WI: Tissues in sac may be bright (gliosis)
MRV: Veins in cephalocele

81. ARNOLD-CHIARI MALFORMATION IV
Extremely rare anomaly probably erroneously included as type of Chiari malformation
Agenesis of cerebellum
Hypoplasia of pons
Small + Funnel-shaped posterior fossa

82. Atlanto-Axial Instability
•A: Rotational
–Around the dens
•B: Translational
–Translation between C1–C2, where transverse lig is disrupted
•C: Distraction:
–Indicating craniocervical dissociation

83. Non-traumatic conditions associated with increase in the atlanto axial
distance:
􀂄 Down syndrome
􀂄 Due to laxity of the transverse ligament
􀂄 Grisel syndrome
􀂄 Atlantoaxial subluxation associated with inflammation of adjacent
soft tissues of the neck
􀂄 Rheumatoid arthritis
􀂄 From laxity of the ligaments and destruction of the articular cartilage
􀂄 Osteogenesis imperfecta
􀂄 Neurofibromatosis
􀂄 Morquio syndrome
􀂄 Secondary to odontoid hypoplasia or aplasia
􀂄 Other arthridities (Psoriasis,Lupus)

84. On the open mouth odontoid view, the combined spread of the lateral
masses of C1 greater than 6.9 mm would indicate rupture of the
transverse ligament.
An atlantoaxial distance greater than 4-5 mm by lateral radiographs,
is indicative of AAI.
Posterior atlanto dental interval (PADI):
Normal range is 19 –32 mm in male & 19 –30mm in females.
Below 19mm, neurological manifestations occur.

85. Rotatory displacement
(Fielding and Hawkins
classification):
􀂄 Type I is simple rotatory
displacement with an intact
transverse ligament.
􀂄 Type II injuries involve
anterior displacement of C1
on C2 of 3-5 mm with one
lateral mass serving as a pivot
point and a deficiency of the
transverse ligament.
􀂄 Type III injuries involve
greater than 5 mm of anterior
displacement.
􀂄 Type IV injuries involve
the posterior displacement of
C1 on C2.

86. TUBERCULOUS AAD
Compression of CMJ could be due to granulation tissue, cold abscess or
bony instability & displacement.
Ligaments are extensively infiltrated by the disease process & give way.
Hyperaemic decalcification occurs.
Radiological findings in 3 stages–
Stage I: Retropharyngeal abscess with ligamentous laxity +, bony
architecture of C1-C2 preserved.
Stage II: Ligamentous disruption with AAD, minimal bone destruction
& retropharyngeal mass +
Stage III: marked destruction of bone, complete obliteration of anterior
arch of C1 & complete loss of odontoid process, marked AAD & O-A
instability.

87. RHEUMATOID ARTHRITIS & CVJ
􀂄 First described by Garrodin 1890.
􀂄 20% of the patients with RA have AAD.
􀂄 AAD is due to loss of tensile strength & stretching of TL due to destructive
inflammatory changes as well as secondary degenerative changes in tissues from
vasculitis.
􀂄 Odontoid process –osteoporosis, angulation/ #.
􀂄 BI occurs secondary to loss of bone in lateral mass of the atlas with resultant rostral
migration of axis vertebra.
􀂄 The lateral mass of atlas may # with lateral displacement of bone fragment.
􀂄 Later on erosion of occipital condyles occur..
A hook like appearance of the odontoid process
occurs seconadary to the cruciate lig pannus
eroding into the odontoid process

88. TRAUMATIC LESIONS OF CVJ
OCCIPITAL CONDYLE #:
MC clinical features are LOC or cranial nerve
damage.
Classification (Anderson & Montesano):
Type I & II are stable injuries while type III is
potentially unstable.
Type I (comminuted fracture with minimal or no displacementType II (basilar skull fracture extending to the occipital condyle)Type III (fracture with a fragment displaced medially from the
inferomedial aspect into the foramen magnum)

89. OCCIPITO-ATLANTAL INSTABILITY:
Traumatic / non traumatic
Traumatic usually fatal, 8% incidence in RTA.
Traynelis classification:

90. # OF ATLAS:
􀂄 Posterior arch #: 2/3rdof all #,
occur at the junction of posterior arch & lateral mass (hyperextension
injury).
Anterior arch #: rare
Jefferson s # : burst # of atlas,
1st described by Geoffrey jefferson in 1920.

91. HANGMAN’S # ( TRAUMATIC SPONDYLOLISTHESIS OF AXIS ):
“Judicial Hanging”- submental knots causes # dislocation of neural arch
of axis.
I:Bilateral pars fractures with translation <3 mm and no angulation; most common
IA:CT: extension of one fracture line into the body and often through the foramen
transversarium(vertebral artery injury may occur)

92. II :C2-3 disc and PLL are disrupted, resulting in translation >3 mm and marked
angulation.
IIA: Fracture line is more oblique than vertical
III:A combination of pars fracture with dislocation of the C2-3 facet
joints

93. ODONTOID #:
Constitute about 7 –14 % of cervical spine #.
Flexion is the MC mechanism of injury causing
anterior displacement of C1 on C2.

94. Type III more stable than type II fractures

95. NEOPLASMS OF CVJ
􀂄 Unusual
􀂄 Metastatic malignancies, such as
carcinoma of the breast, lung,
prostate, kidney and thyroid in
adults; and neuroblastoma , Ewing‟s
tumor, leukemia, hepatoma and
retinoblastoma in children, are most
common.
􀂄 Primary malignancies involving
the cranio cervical junction are
rare(multiple myeloma).
􀂄 Benign tumors are very rare.

96.  Craniovertebral junction (CVJ)
abnormalities involve the osseous
structures and the contained nervous
system.
 -Advances in Digital radiography ,
computed tomography and magnetic
resonance imaging (MRI) have
provided better insight into the
normal anatomy and pathology of this
complex area.