craniovertebral juction 1 by dr mohammad mushtaq
TRANSCRIPT
CranioVertebral Junction
abnormalities
dDr Mohammad Mushtaq
Resident Neurosurgeon
Neurosurgery unit , ATH.
CV JUNCTION
Parts of CV Junction include:-
The Occiput
First Cervical Vertebra (Atlas)
Second Cervical Vertebra (Axis)
Their articulations and
Connecting ligaments
“The C-V junction is a transition site between mobile cranium and relatively rigid spinal column.
It is also the site of the medullo spinal junction”.
Embryology of the CV junction
4th occipital sclerotome, the proatlas and C1 cervical sclerotomegives rise to C1.
Apex of Dense… proatlas.
Body of Dense…C1 and C2 sclerotome.
AXIS develops from five primary and two secondary centers ossifications.
Embryology of the CV junction
The apical segment is not ossified until 3 years of age.
At 12 years it fuses with odontoid to form normal odontoid; failure leads to Os Terminale
Tip of dens
Body of dens
Dens
Anatomy of the CV junction
ATLANTO-AXIAL JOINT:
Normal range of cervical motion is 900 on each side, range of rotation of atlas on axis being 25-530
Rotation of >560 on one side or a R-L diff >80
implies hyper mobility
Rotation of <280 implies hypo mobility
Ligamentous structures of CV junction
Anterior atlanto ocipital membrane
Alar ligament
Apical dense ligament
Tectoral membrane
Cruciate ligament
Posterior atlanto-occipital membrane
CV Junction
Anatomy of the CV junction
Occipital condyles
Atlantoaxial joint
Tectorial Membrane
Lateral mass of atlas
Transverse lig
Cruciate Ligament vertical band
Apical Lig
Alar Lig
Radiological criteria for assessing CVJ instability
predental space in childs upto 8years greater than 5mm,adults greater than 3mm
open mouth view x.ray or coronal ct.........lat masses C1 displacement 6mm
vertical translation b/w clivus and odontoid 2mm,disruption of ligamentous structure
X-ray
X-ray
Lines and Angles
The important lines are
Chamberlain’s line
Wackenheim’s clivus canal line
Mc Gregor’s line (basal line)
McRae,s line
Basal angle
Bull,s angle
Chamberlain’s line
Chamberlain‘s line (Palato-occipital Line)
Joins posterior tip of hard palate to posterior tip of Foramen Magnum (opisthion)Tip of dens below this line ±3 mm >7mm or >1/2 of odontoid def basilar Invagination
Mc Gregor’s line
McGregor’s Line
Line drawn from posterior
tip of Hard palate to lowest part of Occiput
Odontoid tip >4.5mm above = Basilar Invagination
Wackenheim’s Line
Wackenheim's Line drawn along (Clivus canal) line clivus into cervical spinal
canalOdontoid is ventral and tangential to this line
McRae’s Line
McRae's (Foramen Joins anterior and Magnum) line posterior edges of
Foramen magnum
* Tip of odontoid is below this line.** When sagittal diameter of canal <20mm, neurological symptoms
occur – Foramen Magnum Stenosis
Fish gold bimastoid line. a line drawn b/w tips of mastoids. normal odontoid is 2mm above it.
Fish Gold diagastric line. A line drawn b/w the two diagastricnotches. normal distance of atlanto occipital joint should be 10 mm.
Welcher’s Basal Angle
BASAL ANGLE Angle between two lines
drawn from
Nasion to tuberculum sella
Tuberculum sellae to the basion along plane of the clivus
Normal – 1240 - 142
> 1450 = platybasia
< 1300 is seen in achondroplasiaaaasdaaaaaaaaa
Platybasia – refers only to an abnormally obtuse basal angle, may be
asymptomatic, and is not a measure of basilar invagination.
BULL’S ANGLE
Line representing prolongation of hard palate and line joining the midpoints of the ant & post arches of C1.
Normal : <100
Basilar invagination - >130
Lymphatic drainage
Occipitoatlantoaxial joint drain through retropharyngeal gland to deep cervical lymph channels.
Paeds. nasopharyngeal infections cause
inflammatory reaction of CVJ.
C1-2 sublaxation
Refferd as GRISEL SYNDROME
Signs and sympyoms
Myelopathy different degrees of extremities weakness
Brainstem symptoms
Cranial nerves deficit loss of gagreflex,nystagmus,hearing loss
Vascular compromise syncope,vertigo,episodichemiparesis,transient loss of vision,altered conscious level
Restricted neck movement
Neck and occipital pain
Disorders of the CV junction
Congenital bony malformations
Basilar invagination
Anomalies of atlas
Odontoid abnormality
Atlanto-axial instability
Others
Disorders of the CV junction
ACQUIRED MALFORMATIONS
Trauma
Arthritides
Infection
Degeneration
Tumours
Basilar invigination….The upward displacement of upper cervical spine including odontoid through the foramen magnum into posterior fossa.
Pathogenesis
1. Emberyological dysgenesis,genetics, maldevelopment of craniovertebral transition region.
2. Secondary abnormally alignment of fascet joints of atlas and axis leading to progressive slippage of atlas over axis which results in odondoid tip inviginationsuperoir and posterior into cranio cervical cord.
Associated conditions
Down syndrom
Klippel feil syndrom
Acm
Syringomyelia
Rheumatoid arthritis
Post trauma
Paget disease
Classification
Type1. the odontoid tip inviginates into foramen magnum indented into brainstem. atlanto odontoid distance increases. odentoid tip is above CL,McR,wccl.
volume of posterior fossa and Cl angle z normal.
Type2. odontoid tip,ant arch of C1 and clivus migrate superiorly in unison, results in small post fossa causing ACM. odontoid tip is only above CL not wccl,McR.
Type A.
Based on mechanical instability.just like type1 but normal horizontal poition of fascet joint changes into oblique position.which leads progressive slippage.
Type B.
there is congenital dysgenesis , and atlantoaxialjoints were normal or entirely fused.
Treatment
Type1.
85% can be reduced with traction
Transoral decompression and posterior fusion
Its superior to include craniovertebral realignment procedure.
Type2.
only 15% reduced with traction.foramen magnum decompression is appropriate
BASILAR INVAGINATION : CT
Sag & Coronal view
BASILAR INVAGINATION
BASILAR INVAGINATION
KINEMATIC MRI IN BI
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior
type
Anterior Atlanto-Dental Interval (AADI) :
AAS is present when it is >3mm 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
AADI >9mm surgical stabilization
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
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
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
X-rays in neutral position will miss AAS in 48%.
Controlled flexion views always to be done
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
ATLANTO-AXIAL SUBLUXATION (AAS) : anterior type
AAS with cord compression
RISK FACTORS FOR CORD COMPRESSION IN AAS
AADI > 9 mm
PADI < 14 mm
Basilar Invagination, especially if associated with AAS of any degree
Sub axial canal diameter < 14 mm
ATLANTO-AXIAL SUBLUXATION (AAS) : rare
types
Posterior AAS – rare, associated with deficient odontoid process.
Rotatory AAS -
ATLANTO-AXIAL ROTATORY SUBLUXATION
Less common cause of Torticollis in children. Subluxation usually occurs within normal range of rotation of A-A joint.
Fielding types:
Type I :TAL ..intact, facet injury... bilateral (AD less than 3mm)
Type II : TAL.. Injured, facet injury... unilateral (AD 3.1 to 5mm)
Type III : TAL.. Injured, facet injury.... bilateral >5mm AD
Type IV : Incompetence of odotoid with posterior dispacement
DIAGNOSIS:
X-Ray : asymmetry of lateral masses on open mouth odontoid view. Lateral mass that has rotated forwards appear wider and closer to midline.
ATLANTO-AXIAL ROTATORY SUBLUXATION
CT SCAN
ATLANTO-AXIAL ROTATORY SUBLUXATION
Dynamic CT:
Specific Anomalies – Occiput anomalies
Condylus Tertius (IIIrdoccipital condyle) :
when proatlas persists or fails to migrate, an ossified remnant is seen at distal end of clivus
May form pseudo joint with odontoid or ant arch of C1 and limit mobility of CVJ
Increased prevalence of Os Odontoideum seen
ATLAS ASSIMILATION
Represents most cephalic ‘blocked vertebra’
0.25% of population
Usually occurs in association with other anomalies such as BI and Klippel Feil syndrome.
Associated with segmentation failures b/w C2-3 : atlanto-axial subluxation in 50%.
Atlas assimilation with CVJ anomaly
ATLAS ASSIMILATION
classic triad consists of low posterior hairline, short neck and limitation of
neck movements.
KLIPPEL-FEIL SYNDROME :
KLIPPEL-FEIL SYNDROME
Fused vertebrae (usually C2-3 and C5-6 interfaces)
Hemivertebrae
Atlas occipitalization
Spina bifida occulta
Scoliosis
Urogenital, otologicalanomalies, Chiari, syndactyly, Sprengel’setc.
Atlas rachischisis: posterior >> anterior Both together – ‘split atlas’
ODONTOID ABNORMALITIES
Persistent Ossiculum Terminale :
Also called Bergman Ossicle.
Results from failure of fusion of the terminal ossicle to the rest of odontoid
Normally fusion occurs by 12 yrs of age
Stable anomaly when isolated with normal height of dens
Persistent Ossiculum Terminale
May mimic type I odontoid # (avulsion of terminal ossicle) :
difficult to differentiate at times.
Treatment protocol of cv junction
THANK YOU