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DR. SUMIT KAMBLE
DEPT. OF NEUROLOGY
ANATOMY OF CVJ (ARTICULAR)
Occiput & atlas
Upper surfaces of C1 lateral masses is cup-like or
concave which fit into the ball & socket configuration
with occipital condyle.( flexion 10*, extension 25*).
Atlas & axis – 4 synovial joints
2 median –front & back of dens (Pivot variety)
2 lateral –b/w opposing articular facets (Plane variety)
Each joint has its own capsule & synovial cavity.
Rotation is upto 90* & approx ½ occurs at the A-A
ANATOMY OF CVJ(LIGAMENTOUS)
Principal stabilizing ligaments of C1 -
-Transverse atlantal ligament
Secondary stabilizing ligaments of CVJ are more elastic &
weaker than the primary ligaments.
-Anterior & posterior A-O membranes
Structures related are –
Caudal brainstem (Medulla)
Rostral part of spinal cord
Lower cranial (9,10,11 ,12) & upper cervical
nerves (C1,C2, and C3 nerves with both rami).
In cerebellum, only the tonsils, biventral lobules
& the lower part of the vermis (nodule, uvula &
Classification of CV Anomalies
I. Bony Anomalies
A. Major Anomalies
2. Occipitalization of
3. Basilar Invagination
4. Dens Dysplasia
5. Atlanto- axial
B. Minor Anomalies
1. Dysplasia of Atlas
2. Dysplasia of
II. Soft Tissue anomalies
1. Arnold-Chiari Malformation
2. Syringomyelia/ Syringobulbia
Classification of CV Anomalies
Malformation of occipital sclerotomes
Clivus segmentation anomalies
Assimilation of atlas
Malformation of atlas
Assimilation of atlas
Aplasia of atlas arches.
Malformation of axis.
Irregular Atlantoaxial segmentations.
Segmentations failure of c2-c3
Developmental and acquired
At foraman magnum- stenosis
Sec.basilar invagination- OI, Pagets ds, osteomalacia,
1. down syndrome
2. Ehlers danlos syndrome
5. Infection –TB
6. Tumors- Mets, chordom,osteoblastoma, NF
Spontaneous rotatory subluxation- Grisel syndrome
A. Cervical symptoms and signs- pain suboccipital region
radiating vertex, stiffness in 85%
B. Myelopathic Features- long tract involvement and
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
-Open mouth view for dens
Stress X-Rays (neutral, flexion, extention)
CT Scan and 3D reconstruction
MRI conventional and dynamic
Myelogram & Ventriculogram
Craniometry of the CVJ uses a series of lines, planes &
angles to define the normal anatomic relationships of the
These measurements can be taken on plain X rays,3D CT or
No single measurement is helpful.
disadvantage --anatomic structures and planes vary within
a normal range.
Lines and angles used in radiologic diagnosis of C.V
Parameter Normal range limits
B. BASILAR INVAGINATION
C. ATLANTO-AXIAL DISLOCATION *
• Basal angle < 150 degree
• Boogard’s angle < 136 degree
• Bull’s angle < 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.
• Atlanto-odontoid space upto 3 mm in adults
upto 5 mm in children
From tip of hard palate to posterior
tip of Foramen Magnum
It helps to recognise basilar
invagination which is said to be
present if the tip of the dens is >3
mm above this line
Mc Gregor’s line (basal line)
Line drawn from posterior
tip of Hard palate to lowest
part of Occiput
Odontoid tip >5mm above =
Position changed with
flexion and extension so not
Should be used when lowest
part of occipital bone is not
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
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
Welcher’s Basal Angle
Nasion to tuberculum sella
Tuberculum sellae to the basion
along plane of the clivus
Normal – 1240 - 142
> 1400 = platybasia
< 1300 is seen in achondroplasia
prolongation of hard
palate and line joining
the midpoints of the ant
& post arches of C1.
Normal : <100
Basilar invagination -
Boogard ‘s Angle
1st line between Dorsum sellae to Basion & Mc
Average - 1220
Atlantooccipital joint Axis Angle
(Schmidt – Fischer angle)
Range between 124- 127.
Wider in occipital condyle hypoplasia.
FISHGOLD’S DIGASTRIC LINE( Biventer line)
Connects the digastric grooves ( fossae for digastric
muscles on undersurface of skull just medial to mastoid
Tip of the odontoid process and atlanto-occipital joint
normally project 11 mm and 12 mm below this line
Basilar invagination is present when atlanto-occipital
joint projects at or above this line.
FISHGOLD’S BIMASTOID LINE
Line connecting tip of mastoid process.
Odontoid process should be less than 10 mm above this line-
HEIGHT INDEX OF KLAUS
Distance between tip of dens
and tuberculum cruciate
line( line drawn from
tuberculum sella to internal
In basilar invagination <30
margin of the
(posterior margin of
5. posterior pole of
6. anterior arch of
7. posterior arch of
8. odontoid process
Refers only to an abnormally obtuse basal angle, may
be asymptomatic, and is not a measure of basilar
>140 basal angle.
Occipitalization of atlas/assimilation
50% of all cvj anomaly in india.
Failure of segmentation btw last
occipital and first spinal
Gradual or sudden onset by trauma
No movement btw OA –leads
increases stress at AA joint –get
Associated –with basilar
invagination, occipital vertebra, KF
Coronal polytomogram demonstrates complete fusion of the lateral
C-i masses (1) to the occipital condyles (0).
Incidence - 1.4 to 2.5 per 1000 children. It affects both sexes
Neurological symptoms usually occur in third and fourth
decades and vary depending on the area of spinal cord
Restricted neck movement.
Dull, aching pain in the posterior occiput and the neck
Episodic neck stiffness
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
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.
SECONDARY BASILAR INVAGINATION
2. Hurler's syndrome
4. Hajdu-Cheney Syndrome.
5. Paget's disease.
6. Cleidocranial dysostosis
7. Osteogenesis Imperfecta
BI is associated with high incidence of vertebral artery
Topographic types of BI :
Anterior BI : hypoplasia of the basilar process of the
BI of the occipital condyles (Paramedian BI)–Condylar
BI in the lateral condylararea.
Posterior BI: posterior margin of the FM is invaginated.
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.
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
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
GREENBERG’S CLASSIFICATION :
Incompetence of the odontoid process –
Traumatic -# of odontoid
Tumor –1o/ 2o
Incompetence of the TAL –
Inflammatory –Children (pharynx nasopharynx) Adults (RA &
WADIA CLASSIFICATION :
Group I: AAD with occipitalization of atlas & fusion of C2
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.
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
Morquio syndrome -Secondary to odontoid hypoplasiaor
Other arthridities (Psoriasis, Lupus)
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
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
Normal : 17-29 mm at C1
PADI <14mm : predicts
RISK FACTORS FOR CORD
COMPRESSION IN AAS-
AADI > 9 mm
PADI < 14 mm
especially if associated
with AAS of any degree
ATLANTO-AXIAL SUBLUXATION (AAS)
Fielding and Hawkins classification:
Type I- is simple rotatory displacement with an intact
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
Type IV-injuries involve the posterior displacement of C1
Both Type III and IV are highly unstable injuries.
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-
Techniques of fusion vary from sublaminar wiring
techniques like Brooks or Gallie, Halifax clamp, or
transarticular screw of Magerl.
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
Type 4 – Agenesis of odontoid
Type 5 –Total agenesis of
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 Os-
Independent osseous structure
lying cephalad to the axis body in
the location of the odontoid
Anterior arch of the atlas is
rounded and hypertrophic but the
posterior arch is hypoplastic.
Cruciate ligament incompetence
and A-A instability are common
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
Stable when isolated and
of relatively little clinical
Odontoid process is
usually normal in height.
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
Violation of the Chamberlain
line and widening of
atlantooccipital joint axis
Hypoplasia of the basiocciput
may be mild or severe,
depending on the number of
occipital sclerotomes affected.
Clivus-canal angle is typically
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.
Anterior +posterior arch rachischisisis =“split atlas”.
Usually asymptomatic but wide clefts with only a
fibrous covering may lead to atlas instability
Klippel- Feil Syndrome
Decreased range of motion in the
cervical spine m/c
Short, webbed neck
1- Massive fusion of cervical and upper
2 –Fusion of 2 cervical vertebra
,hemivertebra, scoliosis, OA fusion
3-Lower thoracic and upper lumber
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.
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
Due to the hypermobility occurring at the open segments,
can lead to either frank instability or osteoarthritis.
Mechanical symptoms due to joint irritation.
Neurologic symptoms due to root irritation or spinal cord
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
Type III -herniation of cerebellum into a high cervical
Type IV -cerebellar agenesis.
type III and IV -exceedingly rare and incompatible with life .
Chiari type I malformation.
(white line) down to the level of C1 posterior arch.
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
In patients with a CMI,syrinx with scoliosis, the initial
treatment is posterior cervicomedullary decompression.
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
<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.
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.
Bed rest, cervical traction, evacuation of retropharyngeal abscess
& prolonged external immobilization along with ATT.
Indications of Surgery :
Gross bony destruction with instability
Major neurological deficits
Unstable spine following conservative Tx
Anterior decompression with or without fusion
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/#.
Textbook of contemporary neurosurgery vol 1 By Vincent A
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
India, Vol. 50, No. 4, Dec, 2002, pp. 386-397 Review Article