The craniovertebral junction refers to the occiput, atlas, and axis vertebrae and their articulations and ligaments. It is a complex anatomical region forming the transition between the skull and cervical spine. Common craniovertebral junction anomalies include occipitalization of the atlas, basilar invagination, atlantoaxial dislocation, and dens dysplasia. These anomalies can be developmental, post-traumatic, or acquired. Imaging studies including X-rays, CT, MRI are used to classify and evaluate the anomalies. Treatment may involve surgery such as fusion if the anomaly causes spinal cord compression.

1. CRANIO VERTEBRAL JUNCTION
ANOMALIES-ANATOMY AND
EVALUATION
DR SWAPNIL SAMADHIYA
SR NEUROLOGY
GMC KOTA

2. ANATOMY(articular)
CV JUNCTION
• The craniovertebral junction (CVJ) refers anatomically to
the
1. Occiput
2. The first (atlas)
3. Second cervical (axis) vertebral segments
4. Articulations and connecting ligaments.
5. Complex transition between the skull and the upper
cervical spine
6. The brain and spinal cord respectively

4. OCCIPUT
• Surrounds the foramen magnum and consist of three
parts-
1.The squamosal portion (supra-occiput)
2.The basiocciput or clival portion
3.The condylar part (exoocciput)

7. Atlas

8. Axis

10. LIGAMENTOUS ANATOMY
• Occipitoatlantoaxial ligaments are arranged in 4
layers
• Ligaments connecting axis with occipital bone-
Atlanto-occipital membrane
• Paired alar and apical ligament
• Cruciate ligament along with transverse ligament
• Tectorial membrane

11. Ligaments

12. Ligaments

13. BIOMECHANICS
Atlanto-occipital joints Nodding (yes) -Flexion/extension = 13-
15°
• Lateral bending = 8°
Atlanto-axial joints Rotatory (no) -Axial rotation = 37-42°
• Flexion/ extension = 10°
• Axial rotation > 42 °- Dislocation at opposite facet joint
• Axial rotation > 45 °- Angulation & occlusion of I/L vertebral
artery

14. NEURAL
Structures related are –
1. Caudal brainstem (Medulla)
2. Fourth ventricle
3. Rostral part of spinal cord
4. Lower cranial (9,10,11 ,12) & upper cervical nerves
(C1,C2, and C3 nerves with both rami).
5. In cerebellum, only the tonsils, biventral lobules& the
lower part of the vermis (nodule, uvula & pyramid)

15. Classification of CV Anomalies
I. Bony Anomalies
A. Major Anomalies
1. Platybasia
2. Occipitalization of atlas
3. Basilar Invagination
4. Dens Dysplasia
5. Atlanto- axial dislocation
II. Soft Tissue anomalies
1. Arnold-Chiari Malformation
2. Syringomyelia/ Syringobulbia
B. Minor Anomalies
1. Dysplasia of Atlas
2. Dysplasia of occipital condyles, clivus,
etc.

16. Classification of CV Anomalies
Congenital-
1. Malformation of occipital sclerotomes
2. Clivus segmentation anomalies
3. Condylar hypoplasia
4. Assimilation of atlas
• Malformation of atlas
1. Assimilation of atlas
2. Atlantoaxial fusion.
3. Aplasia of atlas arches.
• Malformation of axis.
1. Irregular Atlantoaxial segmentations.
2. Dens dysplasia
• Segmentations failure of C2-C3

17. Developmental and acquired
• At foraman magnum- stenosis
• Sec.basilar invagination- OI, Pagets Ds, Osteomalacia, Rickets, RA.
• Atlantoaxial instability
1. Down syndrome
2. Ehlers danlos syndrome
3. MPS
4. Trauma
5. Infection – TB
6. Tumors- Mets, chordoma,osteoblastoma, NF
• Spontaneous rotatory subluxation- Grisel syndrome

18. Clinical features
A. Cervical symptoms and signs- pain suboccipital region radiating
vertex, stiffness in 85%
B. Myelopathic Features- long tract involvement and wasting
C. CN involvement- IX, X,XI,XI in 20%
D. Vascular - in 15% Transient Attack of V-B insufficiency
E. Sensory symptom of post. column involvement.
F. Cerebellar symptoms/signs- Nystagmus, Ataxia, intention tremor,
dysarthria
G. Features of Raised ICT- usually seen in Pateints Having basilar
impresssion and/or ACM

19. INVESTIGATIONS
• X Rays
1. Antero-posterior view
2. Lateral view
3. Open mouth view for dens
• Stress X-Rays (neutral, flexion, extention)
• CT Scan and 3D reconstruction
• MRI conventional and dynamic
• Myelogram & Ventriculogram
• Angiography

20. CRANIOMETRY
• Craniometry -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.
• No single measurement is helpful.
• Disadvantage --anatomic structures and planes vary within a normal
range

21. 1.Nasion
2.Tuberculum sella
3.Basion (anterior
Margin of the
Foramen magnum)
4. Opisthion
(Posterior margin of
The foramen
Magnum)
5. Posterior pole of
The hard
Palate
6. Anterior arch of
The atlas
7. Posterior arch of
The atlas
8. Odontoid process

22. Lines,angles radiologic diagnosis of C.V
anomalies.

23. Chamberlain’s line
• From tip of hard palate to posterior tip of Foramen Magnum
(opisthion).
• It helps to recognise basilar invagination which is said to be present if
the tip of the dens is >3 mm above this line

24. Mc Gregor’s line (basal line)
• Line drawn from posterior tip
of Hard palate to lowest part
of Occiput
• Odontoid tip >5mm above =
Basilar Invagination
• Position changed with flexion
and extension so not used.
• Should be used when lowest
part of occipital bone is not
Foramen Magnum

25. Wackenheim’s clivus canal line
• Line drawn along
clivus into cervical
spinal canal
• Odontoid is ventral
and tangential to
this line
• If not –suggest AAD
or BI

26. Mc rae’s line ( foramen magnum line)
• Joins anterior and posterior
edges of Foramen magnum
• Tip of odontoid is below this
line.
• When sagittal diameter of
canal <20mm, in patient of
>8 yr of age neurological
symptoms occur – Foramen
Magnum Stenosis

27. Welcher’s Basal Angle
• Nasion to tuberculum sella
• Tuberculum sellae to the basion along plane of the clivus
• Normal – 124- 142
• > 140- platybasia
• < 130 is seen in achondroplasia

28. Boogard ‘s Angle
• 1st line between
Dorsum sellae to
Basion & McRae’s
line.
• Average - 122
• > 135,Basillar
impression

29. Bulls angle
• Line representing
prolongation of hard palate
and line joining the
midpoints of the ant & post
arches of C1.
• Normal : <10
• Basilar invagination ->13

30. Atlantooccipital joint Axis Angle
(Schmidt – Fischer angle)
• Range between 124- 127.
• Wider in occipital condyle
hypoplasia.

31. Fishgold’s digastric line
• Connects the digastric grooves ( fossa for digastric muscles on
undersurface of skull just medial to mastoid process)
• Tip of the odontoid process and atlanto-occipital joint
normally project 11 mm and 12 mm below this line
respectively.
• Basilar invagination is present when atlanto-occipital joint
projects at or above this line.

32. Fishgold’s bimastoid line
• Line connecting tip of mastoid process.
• Odontoid process should be less than 10 mm above this line -BI

33. Height index of klaus
• Distance between tip of
dens and tuberculum
cruciate line( line drawn
from tuberculum sella to
internal occipital
protruberence)
• 40-41mm normal
• In basilar invagination <30
mm

36. Cervical spine-open mouth(dens) view

37. Platybasia
• Refers only to an abnormally obtuse basal angle, may be
asymptomatic, and is not a measure of basilar invagination.
• >140 basal angle.

38. Occipitalization of atlas/assimilation
• 50% of all CVJ anomaly in
India.
• Failure of segmentation btw
last occipital and first spinal
sclerotome.
• Gradual or sudden onset by
trauma
• No movement btw OA –leads
increases stress at AA joint –
get instability
• Associated –with basilar
invagination, occipital
vertebra, KF syndrome

39. Coronal polytomogram complete fusion of
the lateral
C1 masses (1) to the occipital condyles (0).

40. • Incidence - 1.4 to 2.5 per 1000 children. It affects both
sexes equally.
• Neurological symptoms usually occur in third and
fourth decades and vary depending on the area of
spinal cord impingement.
• Clinical Findings-
1. Low hairlines
2. Torticollis
3. Short necks
4. Restricted neck movement.
5. Dull, aching pain in the posterior occiput and the neck
6. Episodic neck stiffness

41. TOPOGRAPHIC FORMS (WACKENHEIM)
Type I: Occipitalization (subtotal) with BI.
Type II: Occipitalization(subtotal) with BI & fusion of 2nd & 3rd cervical
vertebrae.
Type III: occipitalization (Total or subtotal) with BI & maldevelopment
of the transverse ligament,may be associated with various
malformations like C2-C3 fusion,hemivertebra, dens aplasia, tertiary
condyle, etc
Symptoms are due to-absence of a free atlas- TL fails to develop which
causes posterior displacement of axis & compression of the spinal
cord

42. BASILAR INVAGINATION
• Basilar invagination implies that the 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 : primary invagination, which is developmental
and more common, and secondary invagination, which is
acquired.
• Primary invagination can be associated with
occipitoatlantal fusion, hypoplasia of the atlas, a bifid
posterior arch of the atlas, odontoid anomalies.

43. SECONDARY BASILAR INVAGINATION
• 1. Hyperparathyroidism
• 2. Hurler's syndrome
• 3. Rickets/OM/Scurvy
• 4. Hajdu-Cheney Syndrome.
• 5. Paget's disease.
• 6. Cleidocranial dysostosis
• 7. Osteogenesis Imperfecta

44. • BI is associated with high incidence of vertebral artery
anomalies.
Topographic types of BI
• Anterior BI : hypoplasia of the 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.
• Generalised BI

45. SIGNS / SYMPTOMS
• Usually occur in 2nd or 3rd decade.
• Short neck(78%),torticollis (68%)
• Associated ACM & syringomyelia(25 to 35%).
• Motor & sensory disturbances (85%).
• Lower cranial nerves involvement
• Headache & pain in the nape of neck (greater occipital N)
• Raised ICP due to posterior encroachment which causes
blockage of aqueduct of sylvius.
• Compression of cerebellum & vestibular apparatus leading
to vertical or lateral nystagmus(65%) .
• Vertebral artery insufficiency s/s.

47. Atlantoaxial Instability
• Atlantoaxial instability (AAI) is characterized by excessive
movement at the junction between the atlas (C1) and axis
(C2) as a result of either a bony or ligamentous
abnormality.
• Neurologic symptoms can occur when the spinal cord or
adjacent nerve roots are involved
Incidence of AAD –
• 57% of all CVJ anomalies.
• 8.3% of all causes of cervical compression

48. GREENBERG’S CLASSIFICATION
• Incompetence of the odontoid process –
1. Congenital
2. Traumatic -# of odontoid
3. Infections
4. Tumor –pri/sec
• Incompetence of the TAL –
1. Congenital
2. Traumatic
3. Inflammatory –Children (pharynx,nasopharynx) Adults (RA &
ankylosing spondylitis)

49. WADIA CLASSIFICATION
• Group I: AAD with occipitalization of atlas & fusion of C2 & C3.
• Group II: odontoid incompetence due to its maldevelopment with no
occipitalization of atlas.
• Group III: odontoid dislocation but no maldevelopment of dens or
occipitalization of atlas.

50. Non-traumatic conditions associated with
increase in
the atlantoaxial 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)

51. Anterior Atlanto-Dental Interval (AADI)
• AAS is + when >3 mm in adults & >5mm in children
• Measured from posteroinferior margin of ant arch of C1 to the
ant surface of odontoid
• AADI 3-6 mm trans lig. damage
• AADI >6mm alar lig. damage also

52. Posterior Atlanto-Dental Interval (PADI)
• Distance b/w posterior
surface of odontoid &
anterior margin of post ring
of C1
• Considered better method
as it directly measures the
spinal canal
• Normal : 17-29 mm at C1
• PADI <14mm : predicts cord
compression

53. • RISK FACTORS FOR
CORD COMPRESSION
IN-
1. AAS-AADI > 9 mm
2. PADI < 14 mm
3. Basilar Invagination,
especially if associated
with AAS of any
degree

55. ATLANTO-AXIAL SUBLUXATION (AAS)

56. 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.
• Both Type III and IV are highly unstable injuries.

57. TREATMENT
• Type I injuries (stable subluxations) –Collar.
• Type II injuries may be potentially unstable.
• Type III and IV rotatory displacements that are
unstable are treated surgically with a reduction and
C1-2 fusion.
• Techniques of fusion vary from sublaminar wiring
techniques like Brooks or Gallie, Halifax clamp, or
transarticular screw of Magerl.

59. DENS DYSPLASIA
• Type 1 (Os
odontoideum) separate
odontoid process
• Type 2 (Ossiculum
terminale) failure of
fusion of apical
segment with its base
• Type 3 – Agenesis of
odontoid base & apical
segment lies separately.
• Type 4 – Agenesis of
odontoid apical segment
• Type 5 – Total agenesis
of odontoid process.

60. OS ODONTOIDEUM
• At birth odontoid base is separate
from the body of axis by a cartilage
which persists until the age of 8,
later -ossified,or may remain
separate as Osodontoidium.
• Independent osseous structure
lying cephalad to the axis body in
the location of the odontoid
process.
• Anterior arch of the atlas is
rounded and hypertrophic but the
posterior arch is hypoplastic.
• Cruciate ligament incompetence
and A-A instability are common

61. Persistent ossiculum terminale: Bergman
ossicle
• Failure of fusion of the
terminal ossicle to the
remainder of the odontoid
normally by 12 years of age.
• Confused with a type 1
odontoid fracture.
• Stable when isolated and of
relatively little clinical
significance.
• Odontoid process is usually
normal in height.

62. Condylar Hypoplasia
• Occipital condyles are
underdeveloped and have a
flattened -- and widening of the
AO joint axis angle --leading to
BI.
• Lateral masses of the atlas may
be fused to the hypoplastic
condyles, further accentuating
the BI.
• Limits movements at the A-O
joint.
• Violation of the Chamberlain line
and widening of atlantooccipital
joint axis angle

63. Basiocciput Hypoplasia
• Hypoplasia of the basiocciput
may be mild or severe,
depending on the number of
occipital sclerotomes affected.
• Lead-basilar invagination.
• Clivus-canal angle is typically
decreased

64. Posterior Arch Anomalies
• Posterior rachischisis > aplasias and hypoplasia
• Total or partial aplasia of the posterior atlas arch.
• Isolated, is usually asymptomatic, but may be
associated with anterior AA subluxation.
• Simulating Jefferson fracture.

65. SPLIT ATLAS
• Anterior +posterior arch rachischisisis =“split atlas”.
• Usually asymptomatic but wide clefts with only a
fibrous covering may lead to atlas instability

66. Klippel- Feil Syndrome
• Triad
1. Decreased range of motion in
the cervical spine m/c
2. Short, webbed neck
3. Low hairline.
• Type
1- Massive fusion of cervical and
upper thoracic vertebra
2 –Fusion of 2 cervical vertebra
,hemivertebra, scoliosis, OA fusion
3-Lower thoracic and upper lumber
spine anomaly.
4-Sacral agenesis

67. ASSOCIATED CONDITIONS
• Scoliosis- 60%.
• Genito-urinary- 65%. m/c is absence of kidney.
• Sprengel's deformity- 35%
• Cardio-pulmonary-5-15%, m/c V.S.D.
• Deafness-30%, all types, MC mixed.
• Sykinesis-Mirror motions 20%.
• Cranio-cervical abnormalities- (25%)- Includes C1-C2 hypermobility
and instability, BI, Chiari I malformation, diastematomyelia, &
syringomyelia.

68. • 20% of patients may show facial asymmetry, torticollis and
neck webbing (pterygium colli).
• Ptosis of the eye, Duane's eye contracture, lateral rectus
palsy, facial nerve palsy and cleft palate.
• Upper extremity abnormalities, ie. syndactyly , hypoplastic
thumb, supernumary digits and hypoplasia of the upper
extremity.
SYMPTOMS:
1. Due to the hypermobility occurring at the open segments,
can lead to either frank instability or osteoarthritis.
2. Mechanical symptoms due to joint irritation.
3. Neurologic symptoms due to root irritation or spinal cord
compression

69. Arnold-Chiari Malformation
• Type 1- m/c -caudal displacement of peglike cerebellar tonsils
below the level of the foramen magnum, -congenital tonsillar
herniation, tonsillar ectopia, or tonsillar descent.
• Syringomyelia in 50 to 70%.
• Type II -less common and more severe, almost invariably
associated with myelomeningocele. Symptomatic in infancy or
early childhood. -caudal displacement of lower brainstem
(vermis, medulla, pons, 4th ventricle) through the foramen
magnum.
• Type III -herniation of cerebellum into a high cervical
myelomeningocele.
• Type IV -cerebellar agenesis.
Type III and IV -exceedingly rare and incompatible with life .

71. TREATMENT
• No role for prophylactic treatment in an asymptomatic patient with
an incidental CMI.
• All symptomatic patients require surgical treatment.
• In patients with CMI and hydrocephalus, the primary treatment must
be shunting the ventricular system.
• In presence of symptomatic ventral compression from BI or
retroflexion of the odontoid, the treatment is ventral decompression.
• In patients with a CMI, syrinx with scoliosis, the initial treatment is
posterior cervicomedullary decompression.

72. OUTCOMES
• Patients presenting with pain (mainly headache and neck
pain) & weakness without associated atrophy –best results.
• Cranial nerve dysfunction –moderate recovery
• Sensory recovery poor.
• Presence of central cord syndrome due to a syrinx indicative
of poor recovery.
• Three factors most prognostic of poor outcome are atrophy,
ataxia, and scoliosis.
• Brain stem and cerebellar syndromes -good recovery

73. TUBERCULOUS AAD
• <1% of all cases of spinal TB.
• Local pain, restriction of neck movements & acute tenderness
of upper C-spine –Cardinal features.
• Compression of CMJ could be due to granulation tissue, cold
abscess or bony instability & displacement.
• Waxing & waning picture .
• Ligaments are extensively infiltrated .
• Hyperaemic decalcification occurs.

74. 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.

75. TREATMENT:
• Bed rest, cervical traction, evacuation of retropharyngeal
abscess & prolonged external immobilization along with ATT.
Indications of Surgery :
1. Gross bony destruction with instability
2. Major neurological deficits
3. Unstable spine following conservative Tx
Surgery :
1. Posterior fusion
2. Anterior decompression with or without fusion

76. RHEUMATOID ARTHRITIS & CVJ
• 20% of RA have AAD .
• Osteophyte formation (stabilizing effect) does not occur
secondary to deficient osteogenesis(characteristic of RA).
• Loss of tensile strength & stretching of TL due to destructive
inflammatory changes as well as secondary degenerative
changes in tissues from vasculitis--AAD.
• Granulation tissue in the synovial joints.
• Odontoid process –osteoporosis, angulation/#

79. REFERENCES
• Textbook of contemporary neurosurgery vol 1 By Vincent A
Thamburaj
• Apley’s Textbook of Orthopaedics
• A Textbook of Neuroanatomy GARTNER and Rhoton
• Youmans textbook of neurosurgury
• Texbook of neurosurgery –rengachary and shetty .
• Management of Congenital Atlanto-Axial Dislocation
Neurology
• IOSR Journal of dental and medical sciences volume 14,dec
2015
• Uptodate.com
• Radiopedia.org

80. Thank you

82. Indian scenario

84. World scenario