Craniovertebral junction anomaly

1. Craniovertebral junction
Anomalies

2. Definition
• The craniovertebral junction is a collective term that refers to the
occiput ,atlas ,axis and supporting ligaments
• It is a transition zone between a mobile cranium and spinal column
• It encloses the soft tissue structures of cervicomedullary junction i.e
medulla ,spinal cord ,and lower cranial nerve

3. Classification
BONY ABNORMALITY
A. Major Anomalies 1.Platybasia
2.Occipitalization
3.Basilar invagination
4.Dense Dysplasia
5.Atlanto-axial disease
B.Minor Anomalies
1.Dysplasia of Atlas
2.Dysplasia of Condyles,clivus
SOFT TISSUE ANOMALIES
1.Arnold Chiari Syndrome
2.Syringomyelia/Syringobulbia

4. Arnold-Chiari malformation
• Congenital anomalies at the base of the brain
-extension of a tongue of cerebellar tissue posterior to the medulla and cord that extends into the
cervical spinal canal
- caudal displacement of the medulla and the inferior part of the fourth ventricle into the cervical
canal
Type I Herniation of cerebellar Tonsils
Type II Herniation of cerebellar Vermis
Type III Occipital encephalocele
Type IV Lack of cerebellar development

5. Type I
• The most common type, is simply abnormal cerebellar tonsillar herniation
through the foramen magnum (5 mm or more in young adults)
• Classic CM-I is a congenital mesodermal malformation resulting in a
hypoplastic posterior fossa, compressing neural tissue and forcing the
cerebellar tonsils down through the foramen magnum.
• Patients with classic CM-I have a small posterior cranial fossa with
constriction increasing below the Twining line, which extends from the
anterior tuberculum sellae to the internal occipital protuberance.

6. • Patients with achondroplasia can also have a stenosed foramen
magnum and small posterior fossa, but the posterior fossa
constriction is more generalized than in classic CM-I, suggesting an
additional pathogenic mechanism in achondroplasia.
• Crouzon syndrome , Apert syndrome, nonsyndromic craniosynostosis,
achondroplasia, acromegaly, and Paget disease are other causes of a
small posterior fossa.

9. Clinical Presentation
• Female Male -3:1
• The symptoms are those of
• (1) increased intracranial pressure, mainly headache,
• (2) progressive cerebellar ataxia,
• (3) progressive spastic quadriparesis,
• (4) downbeating nystagmus,
• (5) the syndrome of cervical syringomyelia (segmental amyotrophy and sensory loss in the hands
and arms, with or without pain .
• Or the patient may show a combination of disorders of the lower cranial nerves, cerebellum,
medulla, and spinal cord (sensory and motor tract disorders), usually in conjunction with
headache that is mainly occipital.
• This combination of symptoms is easily mistaken for multiple sclerosis or a tumor at the foramen
magnum. The symptoms are usually chronic but may have an acute onset after sustained or
forceful extension of the neck, as, for example, after a long session of dental work, hairdressing in
women, or chiropractic manipulation

10. Chiari-type malformation and
developmental syringomyelia.
T 2-weighted MRI of the low-lying
cerebellar tonsils below the
foramen magnum and behind the
upper cervical cord and
the syrinx cavity in the upper cord.

11. Treatment
• If clinical progression is slight or uncertain, it is probably best to do nothing.
• If disability by way of spasticity, ataxia, pain in the shoulders or arms, or lower cranial-
nerve disease is increasing, upper cervical laminectomy and enlargement of the
foramen magnum are indicated.
• Patients that have headache are operated upon
-if pain has been progressive
-if it is consistently and markedly worsened by cough or similar Valsalva actions
-if there is fainting
• The basic operation is suboccipital and C-1 decompression various forms of shunting may
be added if there is syringomyelia (the shunt is to the adjacent subarachnoid space) or
hydrocephalus.

12. Type II Chiari
• In type II Chiari malformation (with meningomyelocele),
• Progressive hydrocephalus.
• Cerebellar signs
• Lower cranial-nerve abnormalities-laryngeal ,stridor, fasciculations of
the tongue, sternomastoid paralysis (causing head lag when the child
is pulled from lying to sitting), facial weakness, deafness, bilateral
abducens palsies-may be present in varying combinations

13. Basilar Impression
• Caudal settling of the foramen magnum onto the cervical spine,
generally with encroachment of the odontoid process into the
foramen magnum, often resulting in brainstem and/or upper cervical
spinal cord compression.
• Congenital basilar impression may be associated with conditions such
as achondroplasia, occipital dysplasia, Down syndrome, Hurler
syndrome, Klippel-Feil anomaly, and cleidocranial dysplasia.

14. • Some instances of basilar impression are familial. The skeletal
anomaly is often accompanied by anomalies of the neuraxis, including
Chiari I or II malformation and syringomyelia
• Basilar impression can cause compression of the brainstem , the
cerebellum, or (rarely) the vertebral artery, leading to vertebrobasilar
ischemia.
• It is often asymptomatic, particularly when mild and unaccompanied
by other anomalies.

15. Magnetic resonance
image of patient with
basilar impression,
showing brainstem
angulation.

16. Klippel-Feil Anomaly
• Patients with the Klippel-Feil anomaly (congenital synostosis of the
cervical vertebrae) typically have short necks, low hairlines, and
limitation of cervical motion.
• The diagnosis is confirmed by radiographic demonstration of
spontaneously fused cervical vertebrae.
• The condition is congenital, caused by failure of normal segmentation
of the cervical vertebrae between the third and eighth weeks of fetal
development.

17. • Patients may have cervical ribs, predisposing them to thoracic outlet
syndrome.
• Neck pain is common. Hearing loss is the most common cranial nerve
symptom.
• Klippel-Feil syndrome is the anomaly most likely to cause mirror
movements, particularly of the hands.
• Patients with mirror movements can have abnormal clefts or division
of the spinal cord near the Cervicomedullary junction, which can be
detected by MRI or CT myelography .

18. Patient with Klippel-Feil syndrome, showing
short neck.

19. Occipitalization of the Atlas
• Occipitalization or assimilation of the Atlas refers to congenital partial
or complete fusion of the atlas to the occiput
• The anterior arch of the atlas may fuse to the lower end of the clivus,
or the posterior arch of the atlas may fuse to the occiput.
• The anomaly is often asymptomatic until early adult life but may
become symptomatic sooner after trauma.

20. • Unilateral occipitalization of the atlas is one cause of torticollis in
young children.
• The loss of movement between the occiput and atlas increases the
stresses at the atlantoaxial joint, predisposing it to gradual
degeneration or traumatic dislocation.
• Patients with occipitalization of the atlas may have associated
anomalies such as the Klippel-Feil anomaly, basilar impression, or
Chiari malformation

21. Occipitalization of the atlas.
Radiograph shows fusion of lamina of atlas to
occiput (open arrow).
Lamina contains circular arcuate foramina
(arrow) through which vertebral arteries
pass.
Spinous process of atlas (curved arrow) has
fused with C2, making this a partial
incorporation of C1 into the skull base

22. Atlantoaxial Subluxation
• congenital or acquired conditions can disrupt the integrity of the
atlantoaxial joint, leading to its dislocation
• In horizontal subluxation, C1 usually moves anteriorly to C2
• Patients with horizontal atlantoaxial joint subluxation are likely to
compress their spinal cords if the diameter of the spinal canal at the
level of the dens is less than 14 mm.

24. • The movement can be assessed by measuring the separation
between the dens and the anterior arch of C1 on flexion, extension,
and neutral radiographs; in adults, the separation should not exceed
3.5 mm(ADI-atlantodental interval).
• PADI-Posterior atlantodental interval, which is measured between the
posterior border of the dens and the anterior surface of the posterior
arch of C1 (Less than 14 mm)
• Treatment-surgical fusion of C1 and C2

25. SYRINGOMYELIA AND SYRINGOBULBIA
• Hydromyelia is an abnormal dilation of the central spinal canal with excess
CSF contained within the ependymal lining.
• When fluid dissects into the surrounding white matter forming a cystic
cavity or syrinx, the term syringomyelia is applied.
• A syrinx, then, is a cavity in the spinal cord (syringomyelia) or brainstem
(syringobulbia)
• Hydromyelia and syringomyelia often coexist, and use the terms
interchangeably.

26. CLINICAL FEATURE
• LMN signs at the level of the lesion (usually in the arms or lower cranial
nerves)
• Dissociated suspended sensory loss (impaired pain and temperature
sensation but preserved light touch, vibration, and position sense in a cape
or hemicape distribution on the arms and upper trunk)
• Spinal long-tract dysfunction below the level of the lesion.
• Clinical features vary with the size, location, and shape of the cavity; the
rapidity of its evolution; and any associated neurological conditions.
• Symptoms are more related to the pace of evolution of the syrinx than to
its absolute size.

27. • Pain is a prominent symptom in most patients with syringomyelia.
Common complaints include neck ache, headache, back pain,
radicular pain, and areas of segmental dysesthesia
• Painful dysesthesias are most likely to occur at or adjacent to the
caudal extent of the syrinx cavity.
• Some patients have trophic changes corresponding to segmental loss
of pain sensation.
• Syringomyelia can cause neuropathic monoarthritis (Charcot joint),
most commonly in a shoulder or elbow.

28. • Most syringes are in the cervical spinal cord.
• Those developing from hydromyelia are usually associated with Chiari
I or II malformations, communicating hydrocephalus, or abnormalities
at the craniovertebral junction.
• Hydromyelia and larger syringes may be noted as asymptomatic
abnormalities on MRI scans obtained to study the cranial problems.

29. • When the syrinx enlarges as an asymmetrical localized paracentral
outpouching from the Hdromyelia .
• Patients with eccentric cavities have some combination of long-tract
and segmental signs, depending on the location of the cavity and any
associated cord pathology such as tumor, ischemia, or contusion.
• A syrinx associated with a spinal cord tumor or trauma can occur at
any level of the spinal cord

30. Investigation
• CT or MRI can demonstrate a syrinx, MRI is more sensitive for
complete evaluation of the cord and surrounding soft tissues.
• CT myelography can be useful in discerning syringomyelia, which will
commonly fill with contrast on delayed images because of
communication with the CSF through the central canal of the spinal
cord.

31. Magnetic resonance image
demonstrates a large
syringomyelic cavity in the
cervical cord.

32. Treatment
Surgical therapy
- various combinations of suboccipital craniectomy, upper cervical
laminectomy, and/or dural grafting.
-The goal is adequate restoration of normal CSF flow and pressure
across the craniocervical junction.

33. • Thank you