The document discusses the craniovertebral junction (CVJ) anatomy. It describes the key components of the CVJ including the occipital bone, atlas, axis, ligaments, and neurovascular structures. It provides a brief overview of CVJ development from somites. Various CVJ abnormalities are also summarized such as atlantoaxial dislocation (AAD) classifications, basilar invagination, and os odontoideum.

1. DR PRAVEEN K TRIPATHI

2. The term ‘cv junction’ refers to the
occipital bone that surrounds the
foramen magnum and the atlas and the
axis vertebrae.
The C-V junction is a transition site
between mobile cranium and relatively
rigid spinal column. It is also the site of
the medullo spinal junction.
Accounts for approximately 25% of the
vertical height of the entire cervical spine

3.  Meckel , 1815 : manifestation of occipital Vertebrae
 Bell , 1830 : first described spontaneous
Atlantoaxial dislocation
 1886 – giacomini described the first case of congenital aad
 1912Maurice Klippel and Andre Feil
 Chamberlain , 1937 : basilar invagination
 Carl List, in 1941, described the neurological syndromes
accompanying developmental anomalies of the occipital
bone, the atlas, and the axis vertebrae
 1960 – wadia-congenital aads
 Greenberg , 1968 : classified atlantoaxial
Anomalies
 Atul Goel 2014 . Goel's Classification of Atlantoaxial
‘facetal’ dislocation.

4. ● Notochord forms early axial skeleton
● During 4th week gestation, 42 somites formed
o 4 occipital, 8 cervical, 12 thoracic, 5
lumbar, 5 sacral, 8-10 coccygeal
● Each somite differentiates
o outer dermatome
o inner myotome
o medial sclerotome - form vertebrae around
notocord
 4 occipital sclerotomes
● 4th Occipital Sclerotome - Proatlas -
important for CVJ development

5.  Develops from the 4 occipital and upper 2 cervical
somites.
 The mesoderm caudal to neural plate condenses into
four occipital somites, these are the precursors of
occipital sclerotomes.
First Two - Basiocciput
Third - Jugular tubercles
* Fourth occipital sclerotome

Proatlas

6. **DO NOT RESEGMENT

8. Proatlas
Hypocentrum Centrum Neural arch
Anterior tubercle Apex of dens Ventral Dorsal
of clivus & Apical ligament Rostral Caudal

9. First spinal sclerotome
Atlas vertebra is primarily formed from this sclerotome.
Sclerotome division
Hypocentrum Centrum Neural Arch
Anterior arch C1 Dens Inferior portion of
(mid portion the posterior arch
of the odontoid
process and
fused with axis)

10. Second spinal sclerotome
Develops into axis vertebra
Sclerotome division
Hypocentrum Centrum Neural Arch
Disappears Body of axis Facets &
Posterior arch of axis

12.  Constituents of CV junction
 Osseous components and their articulations
 Ligamento-muscular elements
 Neuro-vascular structures
 Characteristics of CV junction
 Mobility at the cost of stability
 Constantly changing structure and kinematics
–even in the post natal period
 Vital neuro-vascular relations

13. Atlas
* Named after the mythical giant who carried the earth on his shoulder.
* Thin Anterior and posterior arches
•Sturdy Lateral masses – made up of a column of superior and inferior
articular facets placed in a vertical line
•No body

14. Axis:
Forms the axis of rotation
Dens is the divorced body of C1
Bifid spinous process
Inferior facet more posterior than superior facet

15. External craniovertebral ligaments

16. Internal Craniovertebral Ligaments

18. POSTERIOR
- POSTERIOR ATLANTOOCCIPITAL MEMBRANE:
EXTENDS FROM OCCIPITAL BONE TO POSTERIOR ARCH
OF ATLAS. IT IS SHARP & THIN & IN DIRECT CONTACT
WITH ANTERIOR CORTEX OF POSTERIOR ARCH OF
ATLAS

19. Anterior Longitudinal
Ligament : Extending
from lower border of
anterior arch of C1 to
body of Axis
Anterior Atlanto-occipital
Membrane : Extends
from anterior edge of
Foramen Magnum to
anterior arch of C1

20. TECTORIAL MEMBRANE
Cephalic extension of
PLL inserted into
processus basilaris
1-2cm above basion

21.  OCCIPITOTRANSVERSE
LIGAMENT: TO BASION
 INFERIOR LOGITUDINAL
BAND: TO AXIS BODY
 TRUE TRANSVERSE
LIGAMENT

22.  STRONG HORIZONTAL
PORTION
 MAINTAINS THE POSITION
OF DENS IN SAGITTAL &
CRANIOCAUDAL DIRECTION
 ARTICULATES WITH
ODONTOID FACET
 INSERTED LATERALLY IN
BONY PROMINENCE
IN INNER ASPECT OF
CONDYLES
 IT IS 8mm IN HEIGHT
AND 2-3 MM THICK IN
MIDLINE

23.  BARKOWS LIGAMENT- FROM
TIP OF DENS TO
ANTEROLATERAL FM RIM
 APICAL LIGAMENT- TIP OF
DENS TO MIDDLE PART OF FM
RIM
 GRUBERS LIGAMENT-
TRANSVERSE LIG TO TIP OF
DENS

24. ALAR LIGAMENT-
 VERY STRONG
LIGAMENT
 6 – 8 mm
 DENS TIP TO LATERAL
PART OF RIM OF FM

25. VERTEBRAL ARTERIES -
Anterior and Posterior
ascending arteries.
CAROTID ARTERY : Anterior
ascending artery.
Forms an apical arterial arcade
in the region of alar ligament
and sends perforators
VENOUS DRAINAGE :
Periodontal venous plexus
and suboccipital venous
sinuses drain to
pharyngovertebral veins

26. LYMPHATIC DRAINAGE : CV JUNCTION DRAINS TO
RETROPHARYNGEAL LYMPH NODES & THEN TO
THE UPPER DEEP CERVICAL CHAIN
RETROGRADE INFECTION OF CV JUNCTION FROM
PHARYNX , SINUSES & RETROPHARYNGEAL AREAS
: GRISEL’S SYNDROME

27. MOVEMENTS :
 FLEXION
 EXTENSION
 SLIDING MOVEMENT
 LATERAL FLEXION
 ROTATION

28. FLEXION & EXTENSION :
JOINTS INVOLVED : OCCIPITOATLANTAL &
ATLANTOAXIAL
AVERAGE RANGE AT OCCIPITOATLANTAL JT. :
13 – 15 DEGREES
ATLANTOAXIAL JT. : 10 DEGREES
FLEXION IS LIMITED BY : TECTORIAL MEMBRANE
DENS BASION CONTACT
EXTENSION LIMITED BY :
STRETCHING OF TEC. M
OPISTHION
POST. ARCH OF ATLAS CONTACT

29. ANTERO-POSTERIOR TRANSLOCATION BETWEEN
DENS & ANT. RING OF ATLAS :
ADULTS : 3mm
YOUNG CHILDREN : 5mm
ADULTS
UPTO 5 mm : RUPTURE OF CRUCIATE LIG.
> 5 mm : RUPTURE OF BOTH
CRUCIATE & ALAR LIG.

30.  JOINT INVOLVED : ATLANTOAXIAL JOINT
 MAXIMUM RANGE : 37 – 42 DEGREES
 > ROTATION LEADS FACET JT. INTERLOCKING
 ROTATION > 32 – 35 DEG. : ANGULATION OF
CONTR. VERT. ARTERY
 > 45 DEG. : IPSILATERAL VA OCCLUSION

31. LATERAL ROTATION : 90 DEG.
JT. INVOLVED : ATLANTOAXIAL & LOWER
C-SPINE
LATERAL FLEXION : SMALL AMPLITUDE
5 – 10 DEG.

32. SLIDING MOVEMENT :
FORWARD OR BACKWARD MOVEMENT OF HEAD
WITHOUT FLEXION OR EXTENSION OF NECK
FORWARD SLIDE : AXIS INCLINES FORWARD
POST. DISPLACEMENT OF AXIS
ANT. ARCH OF ATLAS SLIDES UP
ATLANTOODONTOID SPACE GAP
OCCIPITOODONTOID SPACE GAP
N : 3 – 6 mm
DOUBLE IN FORWARD SLIDE
BACKWARD SLIDE :ANT. ARCH OF ATLAS SLIDES DOWN
POST. ATLANTOOCCIPITAL SPACE

34. Menezes classified CV junction
anomalies into two broad categories
 Congenital (Primary)
 Developmental and Acquired
(Secondary)
CV junction anomalies and AAD
classifications overlap

37. Abnormalities of Foramen magnum
DEFORMITIES OF FORAMEN MAGNUM
N : AP DIAMETER – 30-40 mm
STENOSIS : < 30 mm
ENLARGEMENT : > 40 mm
-MENINGIOMA
- EPIDERMOID
- CYSTIC MALFORMATION
-ACM

38.  AAD is not a disease per se , rather it’s a
manifestation of a spectrum of pathological
states.
 This is a condition in which the atlas(C1) slips
over the axis(C2) in the antero-posterior
direction resulting in neural structure
compression between the two vertebrae.
 A distance of >3mm in an adult & >4.5mm in a
child between posterior surface of anterior Arch
of C1 & anterior surface of dens is thought to be
due to incompetence of Transverse Ligament with
associated instability.

39. Greenberg’s Classification of AAD
I Incompetence of odontoid process
II Incompetence of Transverse Atlantal
ligament
I Incompetence of odontoid process
A. Congenital
1. Type I Separate odontoid: OS odontoideum
2. Type II Free apical segment: Ossiculum
Terminale
3. Type III Agenesis of odontoid base
4. Type IV Agenesis of Apical segment
5. Type V Agenesis of odontoid process totally

41. B. Traumatic
1. Acute
2. Chronic
C. Infectious
e.g Tuberculosis
D. Tumors
1. Primary
2. Metastatic

42. II Incompetence of Transverse Atlantal ligament
A. Congenital:
1. Idiopathic
2. Mongolism
B. Traumatic
1. Acute - Rupture of TAL
2. Chronic - Assimilation of atlas
- Block vertebrae C2 & C3
C. Hyperaemic
1.Infection–Bacterial/viral(Grisel’s
syndrome)/granulomatous
2.Rheumatoid arthritis

43. Wadia proposed the following classification
Group I: AAD with
* Occipitalization of atlas
* Fusion of C2, C3 vertebrae
* Odontoid process dislocated posteriorly
Group II: AAD with
* No occipitalization of atlas
* No Fusion of vertebrae
* Odontoid process dislocated because of its maldevelopment
Group III: AAD with
* No occipitalization
* No fusion of vertebrae
* Odontoid is normal in shape and size to body of the axis.
I & II are usually developmental and III is acquired

44.  Biomechanical
 Translatory
 Rotary
 Radiological
 Mobile
 Fixed
 Clinical
 Reducible
 Irreducible

46. The term Basilar Invagination was
used by Chamberlain in 1939 .
 This is a primary defect implying
prolapse of the vertebral column
into the skull at the base.

47.  Two types of Basilar invagination
 A. Ventral: There is shortening of the
basiocciput so that clivus is short & horizontally
oriented thus displacing the plane of the FM in
an upward direction compared with spinal
column.
 B.Paramesial : Condylar hypoplasia may be
present so that clivus become dorsally displaced
into posterior fossa but may be of normal
length.

48.  BI is commonly associated with an abnormal
odontoid process invaginating into posterior
fossa.
 Axis becomes elongated and the true odontoid
process is small.
 There is abnormal clivus-odontoid articulation.
The resultant abnormal clivus-canal angle
produces an indentation on the pons, medulla or
cervicomedullary junctionin a ventral manner.
 Chiari Malformation is associated with BI in 25 –
30%cases.

49. PSEUDOBASILAR INVAGINATION
OCCIPITALIZATION OF POSTERIOR ARCH OF C1
HYPERTROPHY OF ODONTOID PROCESS
ASSOCIATED FEATURES :
ACM
BILATERAL AGENESIS OF VA

50. OS Odontoideum
Definition – An independent bone cranial to the axis, in the place of dens. It
is not an isolated dens but exists apart from a small hypoplastic dens.
Two types : (Fielding & Griffin)
A. Orthotopic variety: OS lies in the position of dens and moves with atlas
and axis.
B. Dystopic variety: OS lies near the inferior end of clivus & fuses with the
occipital bone and moves in unison with clivus.
Congenital Os Odontoideum Traumatic Os Odontoideum
1. H/o Trauma - often present Always present
2. Location - Usually between base of dens and
usually between the base body of the axis (below superior
and apical segment of the dens facet of axis )
(above superior facet of axis)
3. Line of separation - Always smooth Acutely irregular and not corticated
and corticated
4. Associated congenital anomaly - Absent
often present

51.  Failure of fusion of the terminal ossicle to
remainder of the odontoid process
 Fusion by 12 years of age
 Confused with a type 1 odontoid fracture
(avulsion of the terminal ossicle)
 Differentiation between traumatic or
congenital -difficult
 stable when isolated
 odontoid process is usually normal in
height.

52.  The most interesting feature of the clinical presentation
is the diversity.This is due to compression of the lower
brainstem, cervical spinal cord, cranial nerves, cervical
nerve roots, & vascular supply.
 Presentation may be insidious, or as false localizing sign,
infrequently a rapid neurological progression followed by
death.

53.  The most common symptom is neck pain originating
in suboccipital region with radiation to cranial
vertex region -85%.
 False localising signs: Usually motor monoparesis,
paraparesis, & quadripresis.

54. GENERAL EXAM : Abnormal general physical apperance.
KLIPPEL- FEIL SYNDROME :Triad of Low hairline, short
neck and a webbed neck with limitation of neck movements.
OTHER DYSPLASTIC FEATURES:
high arch palate
poly/syndactyly
pes cavus
scoliosis
sprengel shoulder,

55.  Motor deficits- legs more involved
 Cruciate paralysis
 Posterior tract symptoms- Lhermitte sign
 Central cord syndrome
 Neck pain/ cough headache
 Lower cranial nerve paresis
 Hearing loss(most common)-25%
 Hypoglossal paralysis (Klaus 1969)

56. Sleep apnea and dysphagia
Nystagmus
Gait ataxia
Syncope
Vertigo
Episodic paresis
Transient visual loss.
Due to vertebro basilar insufficiency
Present in 15 – 25% of cases.

57. Importants Points to remember
1. Short neck, low hairline, restricted neck
movements are frequently seen in KF
anomaly, Occipitalization, and basilar
invagination
2. Transient Attacks of VB insufficiency are
usually encountered in Pts. With A-A
dislocation.
3. Several bony and soft tissue anomalies often
co-exist
4. Neurological deficit is usually produced by
A-A dislocation, Basilar Invagination, ACM
and Syringomyelia / Syringobulbia

58.  Conventional antero-posterior and lateral
views will reveal the presence and type of
cranio-vertebral anomaly.
 It will show whether the odontoid is present or
absent and also the integrity of the rings of
atlas and axis.
 Block vertebrae and occipitalisation of atlas
are also visualised.
 The open mouth view shows hypoplastic
odontoid, os odontoideum or ossiculum
terminale with clarity.

59. determine basilar invagination, which
is an upward movement of the base
of the skull in the region of the
foramen magnum.
It is measured by the intracranial
extension of the tip of the odontoid
process.

60.  Chamberlain's line (1939) is drawn from the
posterior lip of the foramen magnum to the dorsal
margin of the hard palate.
 Intracranial projection of up to one third of the
length of the odontoid is normal.
 McGregor's line (1948) is drawn from the upper
surface of the posterior edge of the hard palate to
the most caudal point of the occipital curve of the
skull.
 The tip of the odontoid normally does not extend
more than 4.5 mm above this line.
 McRae's line (1953) defines the opening of the
foramen magnum.

62.  These are the lateral views of the cervical spine in
flexion and extension.
 These are absolutely essential to determine the
presence of atlanto-axial instability and cord
compression.
 The atlanto-dens interval (ADI) is the space between
the anterior aspect of the dens and the posterior
aspect of the anterior arch of atlas.
 This is measured by the distance from the posterior
aspect of the odontoid or axis to the nearest
posterior structure. (Posterior ring of atlas or
foramen magnum).
 in patients with atlantooccipital fusion, those with
less than 19mm of available space behind the
odontoid or atlas were symptomatic.

63. CHAMBERLAIN’S LINE MCRAE’S LINE
 Posterior margin of hard palate to
opisthion( )
 Normal- tip of dens less than 5mm
below this line
 Abnormal- in basilar invagination
 Line from basion to opisthion
( )
 Normal – tip of dens below this
line
 Abnormal-in basilar invagination

64. MCGREGOR’S LINE WACKENHEIM’S LINE
 Posterior margin of hard palate to
lowest part of occipital bone
 Normal- tip of dens less than 7mm
below this line
 Abnormal- in basilar invagination
 Line extrapolated along dorsal
surface of clivus
 Normal – dens should be
tangential or anterior to this line
 Abnormal-in basilar invagination

65. DIGASTRIC LINE BIMASTOID LINE
 Line between incisurae mastoidae
( )
 Normal- 10mm above atlanto-
occipital joint
 Line between tips of mastoid
processes ( )
 Normal – intersects atlanto-
occipital joint

66. WELCHER BASAL ANGLE CLIVUS CANAL ANGLE
 Angle at junction of nasion-
tuberculum and tuberculum-
basion lines
 Normal- 132-140 degree
 Abnormal->143 degree in
platybasia
 Angle at junction of Wackenheim’s
line and posterior vertebral body
line
 Normal – 150-180degree
 Abnormal-<150 degree in platybasia

67. ATLANTOOCCIPITAL JOINT AXIS ANGLE KLAUS INDEX
 Angle formed at junction of lines
along atlanto-occipital joints (
)
 Normal -124-127 degree
 Obtuse in condyle hypoplasia
 Distance between dens and
tuberculum cruciate line ( )
 Normal-40-41mm
 Basilar invagination-<30mm

68.  Skull base flattening
 Primary and secondary
 Bow string deformity
 Increased basal angle
 Decreased clivus canal angle
( )
 Association – basilar
invagination
32 year old gentleman with decreased
clivus canal angle( ) , violation of Chamberlain’s
line( , ) acute angulation, compression of
cervicomedullary juncion ( )
PLATYBASIA

69.  Abnormally high vertebral
column
 Prolapse into skull base
 Secondary- basilar impression
 Chamberlain’s line
 Mc Gregor’s line
 Digastric line
24 year old gentleman with violation of
Chamberlain’s
line( ) and digastric line( ), atlantoaxial
dislocation(atlantodens interval-3.8mm)
BASILAR INVAGINATION

70.  Anterior and posterior arch anomalies
 Total or partial aplasia
 Isolated anterior arch anomalies –rare
 Split atlas
CT axial section showing posterior atlas arch
rachischisis
CT axial section showing partial anterior arch
rachischisis( ) and os odontoideum( )
Hypertrophic anterior arch( ); corticated margins
Jefferson’s fracture
Irregular margins ; normal anterior arch
CONGENITALANOMALIES-ATLAS

71. OS ODONTOIDEUM OSSICULUM TERMINALE
 Separate odontoid process
 Failure of fusion of base with body
of axis
 Bergmann ossicle
 Failure of fusion of apical segment
with base of dens
CONGENITALANOMALIES-AXIS
T1W MRI sagittal section showing os odnotoideum(
CT sagittal section showing os odnotoideum( )
with ossiculum terminale( )

72. KLIPPEL FIEL SYNDROME CHIARI MALFORMATION
 Complex entity causing
cervicovertebral fusion
 Associations- occipito-atlantoid
fusion
 Low lying tonsils
 Associations- basiocciput
hypoplasia, atlanto-occipital
assimilation, platybasia
CONGENITAL SYNDROMES
16 year old lady with herniated tonsils( )
Acute clivocanal angle( ),short clivus( ) and
cervical cord compression
CT sagittal section showing violation of
Chamberlain’s line ( ), atlantooccipital fusion( ),
atlantodens interval of 3.9mm( ),fused C5-C8( )

73.  Congenital
 Acquired
 Traumatic
 Atlantodens interval
3mm - adults
5mm - children
ATLANTOAXIAL DISLOCATION
20 year old man with type 2 dens
fracture(irregular margins( ) and
atlantoaxial dislocation( )
47 year old lady with rheumatoid
arthritis with basilar impression,
sclerosis of atlantoaxial joint( )
and atlantoaxial dislocation( )
18 year old lady with TB,
retropharyngeal collection( ),
lytic area in dens( ) and
atlantoaxial dislocation( )
38 year old lady with increased
atlantodens interval( )
SPONTANEOUS
INFECTIVERHEUMATOID ARTHRITISTRAUMA

74. Lines and angles used in radiologic diagnosis of C.V
anomalies.
Parameter Normal range limits
A. PLATYBASIA
B. BASILAR INVAGINATION
C. ATLANTO-AXIAL DISLOCATION *
• Basal angle < 150 degree
• Boogard’s angle (Angle between the clivus line and McRae's line)< 136 degree
• Bull’s angle (Line drawn between the posterior and anterior arch of
C1. Bull's angle is the angle between this line and the hard palate
plane. < 13 degree
• Chamberlain’s line < one third of odontoid above this line
• Mcgregor’s line < 5 mm
• Mcrae line odontoid lies below this
• Klaus height index > 35 mm
• Atlanto-temporo > 22mm.
mandibular index
• Atlanto-odontoid space upto 3 mm in adults
upto 5 mm in children
• EDFM > 19mm
* May be reducible, partially reducible or irreducible

75. THANK YOU