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
ANATOMY OF CVJ(LIGAMENTOUS)
Principal stabilizing ligaments of C1 -
⚫-Transverse atlantal ligament
Secondary stabilizing ligaments of CVJ are moreelastic &
weaker than the primary ligaments.
⚫-Anterior & posteriorA-O membranes
Structures related are –
⚫Caudal brainstem (Medulla)
⚫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 &
Classification of CV Anomalies
I. Bony Anomalies
3. Basilar Invagination
4. Dens Dysplasia
1. Dysplasiaof Atlas
2. Dysplasia of
I. Soft Tissue anomalies
1. Arnold-Chiari Malformation
2. Syringomyelia/ Syringobulbia
A. Cervical symptomsand 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 symptomof post. column involvement.
F. Cerebellar symptoms/signs- Nystagmus, Ataxia,
intention tremor, dysarthria
G. Featuresof Raised ICT- usually seen in Pateints Having
⚫Craniometryof the CVJ uses a series of lines, planes &
angles todefine the normal anatomic relationshipsof the
⚫These measurementscan be taken on plain X rays,3D CT or
⚫No single measurement is helpful.
⚫disadvantage --anatomicstructuresand planesvarywithin
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
• 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
• Chamberlain’s line
• Mcgregor’s line
• Mcrae line
• Atlanto-odontoid space upto 3 mm inadults
upto 5 mm inchildren
⚫ From tipof hard palate toposterior
tipof Foramen Magnum
⚫ It helps to recognise basilar
invaginationwhich is said to be
present if the tipof thedens is >3
mm abovethis line
Mc Gregor’s line (basal line)
⚫ Line drawn from posterior
tip of Hard palate to lowest
⚫ 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
⚫ Linedrawnalong clivus into
cervical spinal canal
⚫ Odontoid is ventral and tangential
⚫ If not –suggestAAD or BI
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
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
Atlantooccipital joint Axis Angle
(Schmidt – Fischer angle)
⚫Range between 124- 127.
⚫Wider in occipital condyle hypoplasia.
FISHGOLD’S DIGASTRIC LINE( Biventerline)
Connects the digastric grooves ( fossae for digastric
muscleson undersurface of skull just medial to mastoid
Tipof theodontoid process and atlanto-occipital joint
normally project 11 mm and 12 mm below this line
Basilar invagination is presentwhen atlanto-occipital
joint projects at orabove this line.
Occipitalization of atlas/assimilation
⚫50% of all cvj anomaly in india.
⚫Failureof segmentation btw last
occipital and first spinal
⚫ Gradual orsudden onset by trauma
⚫No movement btw OA –leads
increases stress at AA joint –get
⚫Associated –with basilar
invagination, occipital vertebra, KF
⚫ Incidence - 1.4 to 2.5 per 1000 children. Itaffects both sexes
⚫ Neurological symptoms usuallyoccur in third and fourth
decades and vary depending on the area of spinal cord
⚫ Clinical Findings
⚫ Low hairlines
⚫ Short necks
⚫ Restricted neck movement.
⚫ Dull, aching pain in the posteriorocciput 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 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
⚫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.
⚫BI isassociated with high incidence of vertebral artery
Topographic typesof BI :
⚫Anterior BI : hypoplasiaof the basilarprocess of the
⚫BI of theoccipital condyles (Paramedian BI)–Condylar
⚫BI in the lateral condylararea.
⚫Posterior BI: posterior margin of the FM is invaginated.
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.
⚫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
⚫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
⚫GREENBERG’S CLASSIFICATION :
Incompetence of theodontoid process –
Traumatic -# of odontoid
Tumor –1o/ 2o
Adults (RA &
Incompetence of theTAL –
Inflammatory –Children (pharynx nasopharynx)
WADIA CLASSIFICATION :
⚫Group I: AAD with occipitalizationof atlas & fusion of C2
⚫Group II: odontoid incompetence due to its
maldevelopment with no occipitalizationof atlas.
⚫Group III: odontoid dislocation but no maldevelopment of
dens oroccipitalizationof atlas.
Non-traumatic conditions associated with increase in
⚫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
⚫Morquiosyndrome -Secondary toodontoid 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 antarch of C1 to
theant surfaceof odontoid
⚫ AADI 3-6 mm trans lig. damage
⚫ AADI >6mm alar lig. damagealso
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
⚫ 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 anydegree
Fielding and Hawkinsclassification:
⚫Type I- is simple rotatorydisplacement with an intact
⚫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
⚫Type IV-injuries involve the posteriordisplacement of C1
⚫Both Type III and IV are highly unstable injuries.
⚫Type I injuries (stablesubluxations) –Collar.
⚫Type II injuries may be potentiallyunstable.
⚫Type III and IV rotatorydisplacements thatare
unstableare treated surgicallywith a reduction and C1-
⚫Techniques of fusion vary from sublaminar wiring
techniques like Brooks or Gallie, Halifax clamp, or
transarticularscrew of Magerl.
⚫Type 1 (Os odontoideum)
⚫ Type 2 (Ossiculum terminale)
failure of fusion of apical
segmentwith 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
ageof 8, later -ossified,or may
remain separate as Os-
⚫Independent osseous structure
lying cephalad to theaxis body in
the location of the odontoid
⚫Anterior arch of the atlas is
rounded and hypertrophic but the
posteriorarch is hypoplastic.
⚫Cruciate ligament incompetence
and A-A instabilityare common
Persistent ossiculum terminale: Bergman ossicle
⚫Failureof fusion of the
terminal ossicle to the
normally by 12 yearsof 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 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
⚫ Violationof the Chamberlain
line and widening of
atlantooccipital joint axis
Posterior Arch Anomalies
⚫ Posteriorrachischisis > aplasias and hypoplasia
⚫ Total orpartial aplasiaof the posterioratlasarch.
⚫ Isolated, is usuallyasymptomatic, but may beassociated
with anteriorAA subluxation.
⚫ Simulating Jefferson fracture.
Klippel- Feil Syndrome
⚫ Decreased rangeof motion in the
cervical spine m/c
⚫ Short, webbed neck
⚫ Low hairline.
1- Massive fusionof cervical and upper
2 –Fusion of 2 cervical vertebra
,hemivertebra, scoliosis, OA fusion
3 Lower thoracicand upper lumber
4 Sacral agenesis
⚫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.
⚫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
⚫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
⚫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
⚫Type III -herniation of cerebellum intoa high cervical
⚫Type IV -cerebellar agenesis.
type III and IV -exceedingly rareand incompatible with life .
⚫ Chiari type I malformation.
⚫ (white line) down to the level of C1 posterior arch.
⚫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
⚫In patients with a CMI,syrinx with scoliosis, the initial
treatment is posteriorcervicomedullary decompression.
⚫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
⚫<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 .
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.
⚫ 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
⚫ Anteriordecompression with orwithout fusion
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/#.
⚫ Textbook of contemporary neurosurgery vol 1 By Vincent A
⚫ 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