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ECR 2019 / C-0873
Bridging defects-Radio-anatomical review of cranio-vertebral junction anomalies
Congress: ECR 2019
Poster No.: C-0873
Type: Educational Exhibit
Keywords: CT, Conventional radiography, Musculoskeletal system, Head and neck, Foetal imaging, Localisation, Developmental disease
Authors: G. Ilangovan1, R. G. Reddy2; 1Chennai, TA/IN, 2Chennai/IN

Findings and procedure details


Evaluation and assessment of CVJ anomalies is challenging and coming to accurate diagnosis plays a crucial role in the management. Congenital, developmental and acquired anomalies cause atlanto-axial instability or it can affect the vertebra basilar vascular system.


The various causes are broadly classified into




Malformation of the occipital bone

  •  Clivus segmentation
  •  Remanants around foramen magnum
  •  Atals variants
  •  Dens segmentation anomalies
  •  Basilar invagination
  • Condylar hypoplasia
  • Assimilation of atlas

AsMalformations of atlas

  • Asimilation of atlas
  • Atlanto axial fusion
  • Aplasia of atlas arch

Malformation of axis

  • Irregular atlanto axial segmentation
  • Dens dysplasia
  • Ossicular terminalis persistent
  • Os odentoidium
  • Hypoplasia/ aplasia

Segmentation failure of C2-C3


2 Acquired


Abnormalities at foramen magnum

  •  Secondary basilar invagination (pagets disease, rheumatoid arthritis)
  •  Foraminal stenosis(achondroplasia)

Atlanto axial instability

  •  Errors of metabolism
  •  Downs syndrome
  •  Infections (Grisel’s syndrome)
  •  Inflammatory (rheumatoid arthritis)
  •  Traumatic
  •  Tumours – neurofibromatosis
  •  Miscellaneous-syringomyelia, fetal warfarin syndrome, contradi’s syndrome



Congenital CVJ anomalies




Failure of segementation between 4th occipital sclerotome and first spinal sclerotome.Assimilation can be partial or complete.Atlanto-occipital assimilation almost invariably results in basilar invagination. It is also found associated with C2-C3 fusion and atlantoaxial subluxation(figure.4)



Is the flattening of skull base with narrowing/ decreased clival  of angle and increased basal angle.


It Shows a bow string deformity and commonly associated with basilar inavagination(figure.6)



Primary developmental defect implying prolapse of the vertebral column into skull at the base.characterised by abnormally high vertebral column and often found associated with blocked vertebrae and defects of fusion of atlas and occipitalization.(figure.7)


Basilar impression is an acquired form of basilar invagination ,secondary to softening of skull (due to conditions like hyperparathyroidism, pagets disease, osteogenesis imperfecta, rickets ,hurler’s syndrome).Basilar invagination should be suspected when lateral atlantoaxial articulation cannot be visualised in open mouthed projection radiograph.


 4.Basiocciput hypoplasia

Characterised by the shortening of clivus and voilation of chaberlain’s line.often associated with spodyloepiphyseal and spondylometaphyseal dysplasias (figure.9)


5.Os odontoideum

Commonly encounterd congenital anamoly of odontoid.

Anatomical variant of C2(figure.10)

Associated with atalanto axial instability.

  • Morquio syndrome
  • Multiple epiphysial dysplasia



6. Ossiculum terminale

Appears as secondary ossification of dens at the age of 3 to 6yrs and usually fuses bye 12years.

Failure to fuse results in persistent ossiculum terminale .(figure.11)


Bergmann ossicle- Failure of fusion of apical segment with base of dens.


7.klippel fiel syndrome

Defined by segmentation failure at one or multiple levels of cervical spine with or without segmentaion anomalies of thoracic and lumbar vertebrae.


Type 1

Extensive fusion of most of the cervical and upper thoracic spine(figure.12)

Type 2

Fusion at 1 or 2 levels and may include atlanto occipital fusion (mc)

Type 3


Comprised of type 1 or type 2 with coexistant lower thoracic or  lumbar fusion.


8.Chiari Malformation

Congenital hind brain malformation where cerebellar tonsil are displace below the level of foramen magnum.(figure.13)

Low lying cerbellar tonsils with extention 5mm below the foramen magnum(type 1)


Associated basioccciput hypoplasia , atlanto -occipital assimilation , platybasia.


Acquired anomalies.


1.Grisel syndrome

Spontaneous subluxation of atlanto axial joint as a result of spread of infection from parapharyngeal space.

Subluxation is due to metastatic inflamation causing ligamentous stretching and subluxation , muscle spasm , regional hyperimia with decalcification of ligamentous structures.

2.Downs syndrome

Most common CVJ anomaly that occurs in children with downs syndrome is atlantoaxial instability and is also often found associated with myelopathy and spinal cord children with downs syndrome growth of the atlas is slower than that in healthy children. Hypoplasia of the posterior arch of atlas is also seen.



3. Rheumatoid arthritis


Most common inflammatory disease involving the spine and has more predilection for involving craniocervical spine.Three major manifestations of rheumatoid arthritis in cervical spine are basilar inavgination, atlantoaxial instability, and subaxial subluxations.(figure.14)


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