RADIOLOGICAL APPROACH TO CRANIOVERTEBRAL JUNCTION ANOMALIES

Abstract ID: IRIA -1251

Introduction

Knowledge of CVJ anomalies is important as it contains vital structures including cervicomedullary junction

To illustrate the various methods of craniometry used in diagnosing CVJ anomalies

Aims and objectives

Materials and methods

Multimodality radiological assessment of CVJ anomalies along with radiological findings in commonly encountered congenital CVJ anomalies is illustrated

CRANIOMETRY- LANDMARKS

A- nasionB-posterior pole of

hard palateC-anterior arch C1D-odontoid processE-posterior arch C1F- opisthionG- basionH- tuberculum

sellae

A

B

C D E

FG

H

A

B

C

D

E

A- tip of mastoid process

B-occipital condyle

C-odontoid process

D-axis body

E-lateral mass of atlas

CRANIOMETRY - LINES

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

CRANIOMETRY - LINES

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

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

CRANIOMETRY - LINES

CRANIOMETRY - ANGLESWELCHER 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

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

CRANIOMETRY

Chamberlain’s line (palato-occipital line)

Palato–suboccipital line (McGregor line)

Foramen magnum line (McRae line)

Height of the posterior cranial fossa(Klaus Index)

Wackenhein’s clival canal line Bull’s angle (Atlanto-palatal

angle) Atlanto-temporo-

mandibularindex (Fischgold)

• Bimastoid line (Fischgold& Metzer)

• Bidigastric line (Fischgold& Metzer)

• Condylar angle (Schmidt & Fischer)

• Basal angle (Welcher)• Boogard’s angle

Lateral projection Frontal projection

Atlanto-occipital junction

Atlanto-occipital assimilation

Platybasia Basilar invagination

Occipital • Basiocciput hypoplasia• Occipital condyle

hypoplasia• Condylus tertius

Atlas• Posterior arch

anomalies• Anterior arch

anomalies

Axis• Ossiculum terminale• Os odontoideum• Odontoid aplasia

Associated conditions • Chiari malformation• Klippel Fiel syndrome

• Osteogenesis imperfecta• Achondroplasia

CONGENITAL CVJ ANOMALIES-CLASSIFICATION

Failure of segmentation of C1 and skull base

Association – C2-C3 fusion, atlantoaxial subluxation

CT coronal section showing complete atlanto-occipital assimilation on right side and incomplete atlanto-occipital assimilation on left side( )

CONGENITAL ANOMALIES-ATLANTO-OCCIPITALATLANTOOCCIPITAL

ASSIMILATION

CT sagittal section showing complete atlanto-occipital assimilation( ),short clivus( ),violation of Chamberlain’s line( )-basilar invagination and atlantoaxial dislocation( )

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

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

CONGENITAL ANOMALIES-OCCIPITALBASIOCCIPUT HYPOPLASIA CLIVUS CANAL ANGLE

Shortening of clivus Violation of Chamberlain’s line Decreased clivus canal angle

Flattened condyles Widening of atlanto-occipital

joint axis angle ( ) Causes basilar invagination

CT sagittal section showing short clivus ( ), atlantooccipital assimilation ( ) and violation of Chamberlain’s line ( )

CT coronal section showing flattened occipital condyles( ) and widening of atlanto-occipital joint axis angle ( )

Third condyle Ossification remnant

at distal end of clivus Association – os

odontoideum

CT coronal section showing remnant ossification centre at distal end of clivus( )

CONGENITAL ANOMALIES – OCCIPTALCONDYLUS TERTIUS

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 fractureIrregular margins ; normal anterior arch

CONGENITAL ANOMALIES-ATLAS

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

CONGENITAL ANOMALIES-AXIS

T1W MRI sagittal section showing os odnotoideum(

CT sagittal section showing os odnotoideum( ) with ossiculum terminale( )

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( )

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

INFECTIVE RHEUMATOID ARTHRITIS TRAUMA

Understanding of the important land marks and accurate assessment of the lines and angles is crucial in the evaluation of craniovertebral junction anomalies

CONCLUSION

REFERENCES

• Wendy etal, Craniovertebral junction:Normal craniometry and congenital anomalies; Radiographics:1994:14:225-277• Goel A,Basilar invagination,Chiari malformation,syringomyelia:a review,Neurology India, 2009(3):235-246• Tassanawipas etal, magnetic resonance imaging study of the craniocervical junction, J Orth surg, 2005:13(3):228-231• Harris J, The cervicocranium:its radiographic assessment, Radiology 2001;218:337-351