craniovertebral juction 1 by dr mohammad mushtaq

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

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

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


X-rays in neutral position will miss AAS in 48%.

Controlled flexion views always to be done

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.


CT SCAN


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

craniovertebral juction 1 by dr mohammad mushtaq

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