This document discusses various bony and soft tissue anomalies of the craniocervical junction that can cause compression of the brainstem and spinal cord. It outlines different classification systems and measurement lines used to evaluate these anomalies on imaging. Common anomalies discussed include platybasia, basilar invagination, occipito-atlantal fusion, Arnold-Chiari malformation and syringomyelia. Clinical features and approaches to management are also summarized.

1. DR. ABHAY MANGE

2. 1. Foramen magnum
2. Adjacent surrounding occipital bone
(basiocciput)
3. First cervical vertebrae (atlas)
4. Second cervical vertebrae (axis)
 Anomalies may be defects of development and
not necessarily congenital and so may not
manifest at birth

3. I. Bony Anomalies
A. Major Anomalies
1. Platybasia
2. Occipitalization
3. Basilar Invagination
4. Dens Dysplasia
5. Atlanto- axial dis.
B. Minor Anomalies
1. Dysplasia of Atlas
2. Dysplasia of
occipital
condyles, clivus,
etc.
II. Soft Tissue anomalies
1. Arnold-Chiari Malformation
2. Syringomyelia/ Syringobulbia
3. Dandy walker syndrome

4. • Lines , angles and indexes
Chamberlain’s Line
McGregor’s Line
McRae’s Line
 Klaus Height Index
 Basal Angle
 Boogard’s angle

5. CHAMBERLAIN’S
LINE
(Palato-occipital line)
 joins posterior tip of hard
palate to posterior rim of
foramen magnum
 Normally tip of dens lies
3.6 mm below this line.
 In basilar invagination, the
odontoid process bisects
Chamberlain’s line
Clivus
Hard palate
Occiput

6. McRae’s LINE
(Foramen Magnum line)-
Joins anterior and posterior edges
of foramen magnum: sagittal
diameter of foramen magnum.
(Avg – 35mm)
Tip of dens must be below this
line
If effective sagittal space for
cervicomedullary junction is less
than 20 mm in a child older than 8
yrs, neurological deficit is usually
present

7. MCGREGOR’S LINE
(Basal line)-
Joins hard palate to
lowest point of occipital
bone
Tip of dens should not
exceed 5 mm above this
line
Basilar invagination Line
position may vary with
flexion and extension

8. WACKENHEIM’S LINE
( Clivus canal line)
Line drawn along clivus and
extrapolated into cervical
spinal canal.
Odontoid process should be
ventral or tangential to it.
Odontoid process transects
this line in basilar
invagination, atlantoaxial
dislocation and anterior
occipito atlantal dislocation
Clivus
Odontoid
process

9. FISHGOLD’S DIGASTRIC LINE
(Biventer line)-
measured on frontal projection ,Connects the digastric
grooves ( fossae for digastric muscles on undersurface of
skull just medial to mastoid process)
Line is normally 11mm (+/-4mm) above the atlanto-occipital
junction.
Upper limit of position for the odontoid tip
Oblique in unilateral condylar hypoplasia
FISHGOLD’S BIMASTOID LINE
Odontoid process should be less than 10 mm above this line

10. HEIGHT INDEX OF
KLAUS
Distance between tip
of dens and
tuberculum cruciate
line
Nl- 40-41mm
In basilar
invagination-
<30 mm

11. SPINOLAMELLAR LINE
down along the fused spinous
processes of C2 and C3
Normally should intersect
posterior arch of atlas
If atlas is fused, posterior arch is
anterior to the line; posterior
compression of spinal cord may
occur

12. Basal angle
–intersection line from nasion to centre of pitutary fossa
,another line in plan of clivus
N =115 -145
>145 in platybasia
BOOGARDS ANGLE
-angle betn line drawn basion and opsthion and line from
dorsum of sellae n basion
N=<135 IN BI >135
SCHMIDT-FISCHER ANGLE
Angle of axes of atlanto-occipital joints
Normally 124-127 degrees
Angle is wider in condylar hypoplasia

13. BA-BASAL
ANGLE

14. Congenital fusion of cervical vertebrae
Failure of normal segmentation of the cervical vertebrae/somite
between 3rd and 8th weeks of fetal development (rather than a
secondary fusion)
Maurice Klippel and Andre Feil – 1912
Incidence – 1 in 42,000 births ; more in females
Autosomal dominant inheritance – C2-C3 fusion. Autosomal
recessive – C5- C6 fusion
FEIL’S TRIAD :
1. Low posterior hair line
2. Short neck
3. Limitation of head and neck movements / decreased range of
motion in cervical spine

15. Feil’s classification
Type I – massive fusion of many cervical and upper
thoracic vertebrae with synostosis
Type II – fusion of only 1 or 2 vertebrae (with
hemivertebrae , scoliosis, occipito atlantoid fusion)
Type III – presence of lower thoracic and upper lumbar
spine anomalies with I/II
Type IV – sacral agenesis

16. Patients with upper cervical spine involvement
tend to present at an earlier age than those whose
with lower cervical spine involvement
Rotational loss and lateral bending is usually more
pronounced than loss of flexion and extension
because latter movements take place mostly
between occiput and atlas
Scoliosis – some patients congenital due to
involvement of thoracic spine , others scoliosis
compensatory to cervical scoliosis

17. Webbing of soft tissues on each side of the neck
(extending from mastoid process to acromion of
shoulders)- ‘pterygium colli’
Assocd torticollis due to contracture of
sternocleidomastoid muscle or bony abnormalities
Facial asymmetry
Sprengel deformity/ high scapula
Scoliosis and/or kyphosis

18. Musculoskeletal sys- cervical rib, congenital fusion of
ribs, abnormal costovertebral joints, syndactyly,
hypoplastic thumb, hypoplasia of pectoralis major,
hemiatrophy of upper or lower limbs, CTEV, sacral agenesis
Urinary tract abnormalities – agenesis of kidney,
horseshoe kidney, hydronephrosis, tubular ectasia, renal
ectopia, double collecting system
Cardiovascular- VSD, PDA, coarctation of aorta, patent
foramen ovale

19. Deafness (absence of auditory canal and microtia)
Synkinesia- involuntary paired movements of the hand (
mirror movements)
Neurologic deficit- facial nerve Palsy, rectus muscle palsy,
ptosis of eye, cleft palate, etc

20. Cervical spine routine x-ray followed by flexion/extension
lateral X-rays.
These may show flattening and widening of vertebrae,
hemivertebrae or block vertebrae, instability.
MRI with head flexed and extended will most accurately
access subluxation and cord compression along with cord
anomalies.
X-rays of the T-spine because of extension of synostoses
below the neck.

21. Failure of segmentation between the last occipital sclerotome
and the first spinal sclerotome – partial/complete
Anterior arch to clivus : posterior arch to occiput
Signs and symptoms only in second decade of life due to gradual
increasing ligament laxity and instability with aging
Onset of clinical symptoms can be sudden and precipitated by
relatively minor trauma – loss of movt b/w atlas and occiput
increases stress at atlanto axial joint => instability
Neurological symptoms due to Odontoid process projecting into
foramen magnum
Assocd – basilar invagination, occipital vertebra, Klippel Feil
Radiology: cervical spine x-ray (flexion – extension ), CT, MRI
Treatment – non-operative / surgery

22. OS ODONTOIDEUM
independent osseous structure lying cephalad to the
axis body in the location of the odontoid process.
Dystopic – fuses with the occipital bone and moves
with clivus
Orthotopic – lies in the position of normal dens and
moves with atlas and axis vertebrae
HYPOPLASIA/ AGENESIS OF DENS

23. CLASSIFICATION:
Type I A- normal odontoid with occipitalisation of atlas
Type I B- normal odontoid without occipitalisation
Type II- detachment of odontoid from body of axis or
agenesis of part or whole of dens
Diagnosis is radiological. Atlas-Dens interval of more than
5 mm in children and more than 3 mm in adults is
diagnostic

24. Infections(Grisel’s synd):associated with inflammation of
adjacent soft tissues of the neck
Traumatic atlantoaxial / occipitoatlantal dislocation
Degenerative(ligamentous disruption at CV junction)
Inflammatory (RA, ankylosing spondylitis):
Down’s syndrome :due to laxity of transverse ligament
Tumours ( chordoma, syringomyelia, NF )

25. The gap between the
occipital condyles and
the condylar surface of
the atlas is widened to
more than 5 mm.

26. Primary developmental defect
Deformation of the basiocciput – upward indentation or
invagination of base of skull into posterior fossa
Prolapse of the vertebral column upward into the skull at the
base
 BASILAR IMPRESSION –
Acquired form of basilar invagination secondary to softening of
skull Eg. Paget’s disease, OI, hyperparathyroidism, osteomalacia,
rickets
 PLATYBASIA –
 flattening of the skull - Abnormal obtuse basal angle formed by
clivus and floor of anterior fossa – if exceeds 1450

27. Clinical features due to compression of neural structures at
the cervicomedullary junction
Suboccipital headache due to irritation of 2nd cervical
nerve, lower cranial nerve symptoms, cerebellar symptoms(
nystagmus ), progressive quadriparesis
Often associated with other developmental bony anomalies

28. • Type 1- Cerebellomedullary malformation without
meningocoele with variable downward displacement
of cerebellar tonsils into spinal canal
• Type 2. Cerebello-medullary malformation with
meningocoele or meningomyelocoele along with
variable downward displacement of inferior vermis of
cerebellum, brainstem and IVth ventricle into cervical
canal

29. Progressive degenerative/ developmental disorder of the spinal cord,
characterized clinically by brachial amyotrophy, suspended dissociative
sensory loss, and pathologically by cavitation in the central region of the
spinal cord. 90% cases associated with ACM type I.
Types I: Syrinx with obstn of the foramen magnum
Type II: Syrinx without obstn of the foramen magnum
Type III: Syrinx with other diseases of the spinal cord
Type IV: Pure hydromyelia
Syringobulbia: the lower brainstem equivalent of syringomyelia,
usually co-exists

30. Minimally involved patients lead normal lives with only minor
restrictions.
Should avoid contact sports that place neck at risk.
For mechanical symptoms, cervical collar, analgesics, NSAIDS, or
careful traction can be used.
For neurologic compromise a thorough work-up to find the exact area
of irritation, then fusion of the appropriate segments posteriorly.
Decompression may be employed based on the site of the stenosis.
Dislocations and basilar invagination are treated by careful traction
followed by posterior fusion.
Neurologic deficits and persistent pain are indications for surgery

31. MANAGEMENT OF REDUCIBLE DEFORMITIES
Primary goal is stabilization
reducing the compression on brainstem and spinal
cord
MANAGEMENT OF IRREDUCIBLE DEFORMITIES
Decompression
VENTRAL AND DORSAL APPROACHES WITH
FIXATION IF NEEDED