The document discusses the anatomy, classification, and imaging of cervical vertebral anomalies. It describes the following key points: 1. The cervical vertebrae have complex articulations and ligaments that allow flexion, extension, and rotation. Common anomalies involve bony fusions or ligamentous laxity. 2. Anomalies are classified as congenital bony anomalies, soft tissue anomalies like Chiari malformation, or developmental/acquired issues. Atlantoaxial instability and basilar invagination are frequently discussed anomalies. 3. Imaging plays an important role in evaluation. Measurements like Chamberlain's line and Atlanto-dens interval on radiographs help characterize anomalies and risk of cord compression.

1. DR. SUMIT KAMBLE
SENIOR RESIDENT
DEPT. OF NEUROLOGY
GMC, KOTA

2. ANATOMY OF CVJ (ARTICULAR)
Occiput & atlas
⚫ Upper surfaces of C1 lateral masses is cup-like or
concavewhich fit into the ball & socketconfiguration
with occipital condyle.( flexion 10*, extension 25*).
Atlas & axis – 4 synovial joints
⚫2 median –front & back of dens (Pivotvariety)
⚫2 lateral –b/w opposing articular facets (Planevariety)
⚫Each joint has itsowncapsule & synovial cavity.
⚫Rotation is upto 90* & approx ½ occursat the A-A
joint.

3. ANATOMY OF CVJ(LIGAMENTOUS)
Principal stabilizing ligaments of C1 -
⚫-Transverse atlantal ligament
⚫-Alar ligaments
Secondary stabilizing ligaments of CVJ are moreelastic &
weaker than the primary ligaments.
⚫-Apical ligament
⚫-Anterior & posteriorA-O membranes
⚫-Tectorial membrane
⚫-Ligamentum flavum
⚫-Capsular ligaments

5. NEURAL
Structures related are –
⚫Caudal brainstem (Medulla)
⚫Fourth ventricle
⚫Rostral partof spinal cord
⚫Lower cranial (9,10,11 ,12) & uppercervical
nerves (C1,C2, and C3 nerveswith both rami).
⚫In cerebellum, only the tonsils, biventral lobules
& the lower partof thevermis (nodule, uvula &
pyramid)

6. Classification of CV Anomalies
I. Bony Anomalies
A. MajorAnomalies
1. Platybasia
2.Occipitalizationof
atlas
3. Basilar Invagination
4. Dens Dysplasia
5.Atlanto- axial
dislocation
B. MinorAnomalies
1. Dysplasiaof Atlas
2. Dysplasia of
occipital condyles,
clivus, etc.
I. Soft Tissue anomalies
1. Arnold-Chiari Malformation
2. Syringomyelia/ Syringobulbia

7. Classification of CV Anomalies
Congenital-
⚫Malformationof occipital sclerotomes
Clivus segmentationanomalies
Condylar hypoplasia
Assimilationof atlas
⚫ Malformationof atlas
Assimilation of atlas
Atlantoaxial fusion.
Aplasiaof atlas arches.
⚫Malformationof axis.
Irregular Atlantoaxial segmentations.
Dens dysplasia
⚫Segmentations failureof c2-c3

8. 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, chordom,osteoblastoma, NF
⚫Spontaneous rotatorysubluxation- Grisel syndrome

9. Clinical features
A. Cervical symptomsand 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 symptomof post. column involvement.
F. Cerebellar symptoms/signs- Nystagmus, Ataxia,
intention tremor, dysarthria
G. Featuresof Raised ICT- usually seen in Pateints Having
basilar impresssionand/orACM

10. INVESTIGATIONS
⚫ X Rays
-Antero-posteriorview
-Lateral view
-Open mouth view fordens
⚫ Stress X-Rays (neutral, flexion, extention)
⚫ CT Scan and 3D reconstruction
⚫ MRI conventional and dynamic
⚫ Myelogram & Ventriculogram
⚫ Angiography

11. CRANIOMETRY:
⚫Craniometryof the CVJ uses a series of lines, planes &
angles todefine the normal anatomic relationshipsof the
CVJ.
⚫These measurementscan be taken on plain X rays,3D CT or
on MRI.
⚫No single measurement is helpful.
⚫disadvantage --anatomicstructuresand planesvarywithin
a normal range.

12. 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
• Boogard’s angle
• Bull’s angle
< 150 degree
< 136 degree
< 13 degree
< onethird of odontoidabove this line
< 5 mm
odontoid lies below this
> 35 mm
> 22mm.
• Chamberlain’s line
• Mcgregor’s line
• Mcrae line
• Klausheightindex
• Atlanto-temporo
mandibular index
• Atlanto-odontoid space upto 3 mm inadults
upto 5 mm inchildren

13. Chamberlain’s line
⚫ From tipof hard palate toposterior
tipof Foramen Magnum
(opisthion).
⚫ It helps to recognise basilar
invaginationwhich is said to be
present if the tipof thedens is >3
mm abovethis line

14. Mc Gregor’s line (basal line)
⚫ Line drawn from posterior
tip of Hard palate to lowest
partof 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.

15. Wackenheim’s clivus canal line
⚫ Linedrawnalong clivus into
cervical spinal canal
⚫ Odontoid is ventral and tangential
tothis line
⚫ If not –suggestAAD or BI

16. Mc rae’s line ( foramen magnum line)
⚫ Joinsanteriorand posterioredges of Foramen magnum
⚫Tipof odontoid is below this line.
⚫When sagittal diameterof canal <20mm, in patientof >8
yrof age neurological symptoms occur – Foramen
Magnum Stenosis

17. Welcher’s Basal Angle
⚫Nasion to tuberculum sella
⚫Tuberculum sellae to the basion
along planeof theclivus
⚫Normal – 1240 - 142
⚫> 1400 = platybasia
⚫< 1300 is seen in achondroplasia

18. Bulls angle
⚫Line representing
prolongation of hard
palateand line joining
the midpointsof theant
& post arches of C1.
⚫Normal : <100
⚫Basilar invagination -
>130

19. Boogard ‘s Angle
⚫1s
t
line between Dorsum sellae to Basion & Mc
Rae’s line.
⚫Average - 1220
⚫> 1350
⚫Basillar impression

20. Atlantooccipital joint Axis Angle
(Schmidt – Fischer angle)
⚫Range between 124- 127.
⚫Wider in occipital condyle hypoplasia.
O
C2
AA JT
AO JT
C1 C1

21. FISHGOLD’S DIGASTRIC LINE( Biventerline)
Connects the digastric grooves ( fossae for digastric
muscleson undersurface of skull just medial to mastoid
process)
 Tipof theodontoid process and atlanto-occipital joint
normally project 11 mm and 12 mm below this line
respectively.
 Basilar invagination is presentwhen atlanto-occipital
joint projects at orabove this line.

22. FISHGOLD’S BIMASTOID LINE
⚫Lineconnecting tipof mastoid process.
⚫Odontoid process should be less than 10 mm above this line-
BI

23. HEIGHT INDEX OF KLAUS
⚫Distance between tipof dens
and tuberculum cruciate
line( line drawn from
tuberculum sella to internal
occipital protruberence)
⚫40-41mm normal
⚫In basilar invagination <30
mm

24. 1.nasion
2.tuberculum sella
3.basion (anterior
margin of the
foramen magnum)
4.opisthion
(posterior margin of
the foramen
magnum)
5.posteriorpole of
the hard
palate
6.anteriorarchof
theatlas
7. posteriorarchof
theatlas
8. odontoid process

28. Platybasia
⚫Refersonly toan abnormallyobtuse basal angle, may
be asymptomatic, and is not a measure of basilar
invagination.
⚫>140 basal angle.

29. Occipitalization of atlas/assimilation
⚫50% of all cvj anomaly in india.
⚫Failureof segmentation btw last
occipital and first spinal
sclerotome.
⚫ Gradual orsudden onset by trauma
⚫No movement btw OA –leads
increases stress at AA joint –get
instability
⚫Associated –with basilar
invagination, occipital vertebra, KF
syndrome

30. fusionof the lateral
Coronal polytomogramdemonstratescomplete
C-i masses (1) totheoccipital condyles (0).

31. ⚫ Incidence - 1.4 to 2.5 per 1000 children. Itaffects both sexes
equally.
⚫ Neurological symptoms usuallyoccur in third and fourth
decades and vary depending on the area of spinal cord
impingement.
⚫ Clinical Findings
⚫ Low hairlines
⚫ Torticollis
⚫ Short necks
⚫ Restricted neck movement.
⚫ Dull, aching pain in the posteriorocciput and the neck
⚫ Episodic neck stiffness

33. 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 orsubtotal) with BI &
maldevelopment of the transverse ligament. may be
associated with various malformations like C2-C3 fusion,
hemivertebra, dens aplasia, tertiarycondyle, etc
⚫Symptomsaredue to-absence of a freeatlas- TL fails to
develop which causes posterior displacement of axis &
compression of the spinal cord

34. BASILAR INVAGINATION
⚫Basilar invagination implies that the floor of the skull
is indented by the upper cervical spine, & hence the tip
of odontoidis 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 occipito
atlantal fusion, hypoplasia of the atlas, a bifid
posterior arch of the atlas, odontoid anomalies.

35. 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

36. ⚫BI isassociated with high incidence of vertebral artery
anomalies.
Topographic typesof BI :
⚫Anterior BI : hypoplasiaof the basilarprocess of the
occipital bone.
⚫BI of theoccipital condyles (Paramedian BI)–Condylar
hypoplasia
⚫BI in the lateral condylararea.
⚫Posterior BI: posterior margin of the FM is invaginated.
⚫Unilateral BI.
⚫Generalised BI

37. SIGNS / SYMPTOMS
Usuallyoccur in 2nd or 3rd decade.
⚫ Short neck(78%),torticollis (68%)
⚫ Associated ACM & syringomyelia(25 to 35%).
⚫ Motor & sensorydisturbances (85%).
⚫ Lowercranial nerves involvement
⚫ Headache & pain in the napeof neck (greateroccipital N)
⚫ Raised ICP due to posteriorencroachmentwhich causes
blockageof aqueductof sylvius.
⚫ Compression of cerebellum & vestibularapparatus leading to
vertical or lateral nystagmus(65%) .
⚫ Vertebral artery insufficiencys/s.

39. Atlantoaxial Instability
⚫Atlantoaxial instability (AAI) is characterized byexcessive
movement at the junction between the atlas (C1) and axis
(C2) as a result of eithera bony or ligamentous
abnormality.
⚫Neurologic symptomscan occurwhen the spinal cord or
adjacent nerve roots are involved.
Incidence of AAD –
⚫57% of all CVJ anomalies.
⚫8.3% of all causesof cervical compression

40. ⚫GREENBERG’S CLASSIFICATION :
Incompetence of theodontoid process –
Congenital
Traumatic -# of odontoid
Infections
Tumor –1o/ 2o
Adults (RA &
Incompetence of theTAL –
Congenital
Traumatic
Inflammatory –Children (pharynx nasopharynx)
ankylosing spondylitis)

41. WADIA CLASSIFICATION :
⚫Group I: AAD with occipitalizationof atlas & fusion of C2
& C3.
⚫Group II: odontoid incompetence due to its
maldevelopment with no occipitalizationof atlas.
⚫Group III: odontoid dislocation but no maldevelopment of
dens oroccipitalizationof atlas.

42. Non-traumatic conditions associated with increase in
theatlantoaxial distance:
⚫Down syndrome -Due to laxityof the transverse ligament
⚫Grisel syndrome –Atlantoaxial subluxation associated with
inflammation of adjacent soft tissues of the neck
⚫Rheumatoid arthritis-From laxityof the ligamentsand
destruction of thearticularcartilage
⚫Osteogenesis imperfecta
⚫Neurofibromatosis
⚫Morquiosyndrome -Secondary toodontoid hypoplasiaor
aplasia
⚫Other arthridities (Psoriasis, Lupus)

43. Anterior Atlanto-Dental Interval (AADI)
⚫ AAS is + when >3 mm in adults & >5mm in children
⚫ Measured from posteroinferior margin of antarch of C1 to
theant surfaceof odontoid
⚫ AADI 3-6 mm  trans lig. damage
⚫ AADI >6mm  alar lig. damagealso

44. PosteriorAtlanto-Dental Interval (PADI) :
⚫ Distance b/w posterior
surface of odontoid &
anterior marginof 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

45. RISK FACTORS FOR CORD
COMPRESSION IN AAS-
⚫AADI > 9 mm
⚫PADI < 14 mm
⚫Basilar Invagination,
especially if associated
with AAS of anydegree

47. ATLANTO-AXIAL SUBLUXATION (AAS)

48. Fielding and Hawkinsclassification:
⚫Type I- is simple rotatorydisplacement with an intact
transverse ligament.
⚫Type II- injuries involve anteriordisplacement of C1 on C2
of 3-5 mm with one lateral mass serving as a pivot point
and adeficiency of the transverse ligament.
⚫Type III -injuries involve greater than 5 mm of anterior
displacement.
⚫Type IV-injuries involve the posteriordisplacement of C1
on C2.
⚫Both Type III and IV are highly unstable injuries.

49. TREATMENT-
⚫Type I injuries (stablesubluxations) –Collar.
⚫Type II injuries may be potentiallyunstable.
⚫Type III and IV rotatorydisplacements thatare
unstableare treated surgicallywith a reduction and C1-
2 fusion.
⚫Techniques of fusion vary from sublaminar wiring
techniques like Brooks or Gallie, Halifax clamp, or
transarticularscrew of Magerl.

50. DENS DYSPLASIA
⚫Type 1 (Os odontoideum)
separateodontoid process
⚫ Type 2 (Ossiculum terminale)
failure of fusion of apical
segmentwith 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.

51. OS ODONTOIDEUM
⚫At birth odontoid base is separate
from the body of axis by a
cartilage which persists until the
ageof 8, later -ossified,or may
remain separate as Os-
odontoidium.
⚫Independent osseous structure
lying cephalad to theaxis body in
the location of the odontoid
process.
⚫Anterior arch of the atlas is
rounded and hypertrophic but the
posteriorarch is hypoplastic.
⚫Cruciate ligament incompetence
and A-A instabilityare common

52. Persistent ossiculum terminale: Bergman ossicle
⚫Failureof fusion of the
terminal ossicle to the
remainderof theodontoid-
normally by 12 yearsof age.
⚫Confused with a type 1
odontoid fracture.
⚫Stable when isolated and
of relatively little clinical
significance.
⚫Odontoid process is
usually normal in height.

53. Condylar Hypoplasia:
⚫ Occipital condyles are
underdeveloped and havea
flattened -- and widening of
the AO jointaxis angle --
leading to BI.
⚫ Lateral masses of the atlas
may be fused to the
hypoplastic condyles, further
accentuating the BI.
⚫ Limits movementsat the A-O
joint.
⚫ Violationof the Chamberlain
line and widening of
atlantooccipital joint axis
angle

54. Basiocciput Hypoplasia:
⚫Hypoplasiaof the basiocciput
may be mild or severe,
depending on the numberof
occipital sclerotomes affected.
⚫Lead-basilar invagination.
⚫Clivus-canal angle is typically
decreased

55. Posterior Arch Anomalies
⚫ Posteriorrachischisis > aplasias and hypoplasia
⚫ Total orpartial aplasiaof the posterioratlasarch.
⚫ Isolated, is usuallyasymptomatic, but may beassociated
with anteriorAA subluxation.
⚫ Simulating Jefferson fracture.

56. SPLIT ATLAS
⚫Anterior +posteriorarch rachischisisis =“splitatlas”.
⚫Usuallyasymptomatic butwideclefts with only a
fibrouscovering may lead toatlas instability

57. Klippel- Feil Syndrome
Triad
⚫ Decreased rangeof motion in the
cervical spine m/c
⚫ Short, webbed neck
⚫ Low hairline.
Type
1- Massive fusionof cervical and upper
thoracicvertebra
2 –Fusion of 2 cervical vertebra
,hemivertebra, scoliosis, OA fusion
3 Lower thoracicand upper lumber
spineanomaly.
4 Sacral agenesis

58. 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
hypermobilityand instability, BI, Chiari I malformation,
diastematomyelia, & syringomyelia.

59. ⚫20% of patients mayshow facial asymmetry, torticollis and
neck webbing (pterygiumcolli).
⚫Ptosis of theeye, Duane'seye contracture, lateral rectus
palsy, facial nerve palsyand cleft palate.
⚫Upperextremityabnormalities, ie. syndactyly, hypoplastic
thumb, supernumarydigitsand hypoplasiaof the upper
extremity.
SYMPTOMS:
⚫Due to the hypermobilityoccurring at theopen segments,
can lead toeither frank instabilityorosteoarthritis.
⚫Mechanical symptomsdue to joint irritation.
⚫Neurologic symptomsdue to root irritation or spinal cord
compression

60. Arnold-Chiari Malformation
⚫Type 1- m/c -caudal displacement of peglikecerebellar 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
orearlychildhood. -caudal displacement of lower brainstem
(vermis, medulla, pons, 4th ventricle) through the foramen
magnum.
⚫Type III -herniation of cerebellum intoa high cervical
myelomeningocele.
⚫Type IV -cerebellar agenesis.
type III and IV -exceedingly rareand incompatible with life .

61. ⚫ Chiari type I malformation.
⚫ (white line) down to the level of C1 posterior arch.

62. TREATMENT:
⚫No role forprophylactic treatment in an asymptomatic
patientwith an incidental CMI.
⚫All symptomatic patients requiresurgical treatment.
⚫In patients with CMI and hydrocephalus, the primary
treatment must be shunting theventricularsystem.
⚫In presenceof symptomaticventral 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 posteriorcervicomedullary decompression.

63. OUTCOMES:
⚫Patients presenting with pain (mainly headache and neck
pain) & weakness withoutassociated atrophy –best results.
⚫Cranial nervedysfunction –moderate recovery
⚫Sensory recovery poor.
⚫Presence of central cord syndrome due toa syrinx-
indicativeof poor recovery
.
⚫Three factors most prognostic of pooroutcome are atrophy,
ataxia, and scoliosis.
⚫Brain stem and cerebellar syndromes -good recovery

64. TUBERCULOUS AAD
⚫<1% of all cases of spinal TB.
⚫Local pain, restriction of neck movements & acute
tenderness of upper C-spine –Cardinal features.
⚫Compressionof CMJ could bedue togranulation tissue,
cold abscess or bony instability & displacement.
⚫Waxing & waning picture .
⚫Ligaments areextensively infiltrated .
⚫Hyperaemicdecalcification occurs.

65. Radiological findings in 3 stages–
⚫Stage I: Retropharyngeal abscess with ligamentous laxity +,
bonyarchitecture of C1-C2 preserved.
⚫Stage II: Ligamentous disruptionwith AAD, minimal bone
destruction & retropharyngeal mass +
⚫Stage III: marked destruction of bone, complete
obliteration of anteriorarch of C1 & complete loss of
odontoid process, marked AAD & O-A instability.

66. TREATMENT:
⚫ Bed rest, cervical traction, evacuation of retropharyngeal abscess
& prolonged external immobilizationalong with ATT.
Indicationsof Surgery :
⚫ Gross bonydestruction with instability
⚫ Major neurological deficits
⚫ Unstablespine following conservativeTx
Surgery :
⚫ Posteriorfusion
⚫ Anteriordecompression with orwithout fusion

67. RHEUMATOID ARTHRITIS & CVJ
⚫20% of RA have AAD.
⚫Osteophyte formation (stabilizing effect) does not occur
secondary todeficient osteogenesis(characteristic of RA).
⚫Loss of tensile strength & stretching of TL due to
destructive inflammatorychanges as well as secondary
degenerativechanges in tissues from vasculitis--AAD.
⚫Granulation tissue in thesynovial joints.
⚫Odontoid process –osteoporosis, angulation/#.

69. REFFERENCES-
⚫ Textbook of contemporary neurosurgery vol 1 By Vincent A
Thamburaj
⚫ Apley’s Textbook of Orthopaedics
⚫ A Textbook of Neuroanatomy GARTNER and Rhoton
⚫ Youmanstextbook of neurosurgury
⚫ Texbook of neurosurgery –rengacharyand shetty.
⚫ Managementof Congenital Atlanto-Axial Dislocation Neurology
India, Vol. 50, No. 4, Dec, 2002, pp. 386-397 Review Article
⚫ Uptodate.com
⚫ Radiopedia.org