Craniosynostosis Chiari Dandy walker malformation

CRANIOSYNOSTOSIS,
CHIARI MALFORMATIONS,
DANDY WALKER CONTINIUM,
CVJ ANOMALIES
DR MYTHILI K R

CRANIOSYNOSTOSIS
• a/k/a Craniostenosis, Sutural synostosis and Cranial dysostosis
• Can be non-syndromic (70-75% of cases) or syndromic
• The calvaria normally expands during infancy and early childhood to
accommodate the growing brain.
• This mostly occurs at narrow seams of undifferentiated mesenchyme—the
cranial sutures—that lie between adjacent bones.
• Normal sutures permit skull growth perpendicular to their long axis.

• As long as the brain grows rapidly, the calvaria expands.
• As brain growth slows, the sutures close.
Normal order of closure:
Metopic suture
Coronal suture
Lambdoid suture
Sagittal suture

• Craniosynostosis occurs when osseous obliteration of one or more
sutures occurs prematurely.
• Skull distortion occurs from a combination of
• (1) Restriction of skull growth perpendicular to the prematurely
fused suture and
• (2) Compensatory overgrowth at the non fused sutures.
• Can be associated with neurological or vascular compromise.
• Severe deformities can be cosmetically disfiguring and socially
stigmatizing

ROLE OF IMAGING IN CRANIOSYNOSTOSIS:
• Recognition of craniosynostoses,
• Identification of coexisting brain anomalies,
• Preoperative treatment planning, and
• Postoperative follow up.

NONSYNDROMIC CRANIOSYNOSTOSIS
• Sagittal suture (60%) > Coronal (22%) > Metopic (15%) sutures.
• Lambdoid suture involvement is rare.
• Between 85-90% of these involve only a single suture, whereas 5-15% are
multi suture synostoses.

CLASSIFICATION:
Based on shape of the skull
• Scaphocephaly or dolichocephaly
(long and narrow),
• Brachycephaly (broad and flattened),
• Trigonocephaly (triangular at the
front),
• Plagiocephaly (skewed).

SEVERE DEFORMITIES MAY LEAD TO
• Hydrocephalus,
• Elevated intracranial pressure,
• Compromised cerebral blood flow, and
• Airway obstruction.

SCAPHOCEPHALY (DOLICHOCEPHALY)
• Caused by sagittal suture synostosis.
• Demonstrate an elongated skull with
decreased transverse and increased AP
measurements.
• Forehead bossing is common.
• In severe cases, the sagittal suture is
elevated, and the elongated ridge of bone
resembles the keel of a ship.

BRACHYCEPHALY
• Caused by bicoronal or bilambdoid synostosis.
• In such cases, the skull appears widened in
the transverse dimension while shortened
from front to back.
• Craniofacial deformities such as bilateral
"harlequin" orbits—peculiar bony deformities
seen as elevation/elongation of the
superolateral orbit walls—are common.

TRIGONOCEPHALY
• Caused by synostosis of the metopic
suture.
• The forehead appears wedge-shaped
or triangular.
• Hypotelorism is common.

PLAGIOCEPHALY:
• Calvaria is very asymmetric.
• Unilateral single or asymmetric multiple sutural
fusions can produce this appearance.
• In unilateral coronal synostosis, the hemicalvaria
is shortened and pointed; it may be associated
with a unilateral "harlequin" eye.
• If the lambdoid suture is fused, the skull assumes
a more trapezoid appearance with occipital
flattening and posterior ear displacement.

TURRICEPHALY:
• "Towering" skull is a more
extreme deformity caused
by bicoronal or bilambdoid
synostosis.

KLEEBLATTSCHÄDEL:
• Also known as "cloverleaf" skull.
• Bicoronal and bilambdoid synostoses cause an unusual pattern of bulging
temporal bones, towering skull, and shallow orbits.

OXYCEPHALY :
The coronal, sagittal, and lambdoid sutures are
all fused in oxycephaly.

SYNDROMIC CRANIOSYNOSTOSES
• Account for just 25-30% of all cranial synostoses.
• Apert Syndrome
• Crouzon syndrome
• Saethre - Chotzen Syndrome
• Waardenburg Syndrome
• Greig Syndrome
• Pfieffer syndrome
• Carpenter syndrome

APERT SYNDROME
• Also known as acrocephalosyndactyly type
1.
• Craniosynostosis with hypertelorism,
midface hypoplasia, and cervical spine
anomalies is common.
• Severe symmetric hand and foot syndactyly
is present in most patients.
• Bilateral coronal synostosis is the most
common calvarial anomaly.
• Intracranial anomalies are Hydrocephalus,
callosal dysgenesis, and abnormalities of the
septi pellucidi

CROUZON SYNDROME
• Acrocephalosyndactyly type2, also known as
Apert-Crouzon or Crouzon syndrome, shows
many of the same features seen in Apert
syndrome.
• Affected individuals more commonly have
multiple suture calvaria involvement.
• Hypertelorism and exophthalmos are
prominent features.
• Both types 1 and 2 acrocephalosyndactyly
are associated with FGFR2 mutations.

SAETHRE - CHOTZEN SYNDROME
• Also known as acrocephalosyndactyly type 3.
• A specific mutation in TWIST1 has been associated with this
disorder.
• Craniosynostosis – typically coronal.
• Duplicated distal phalanges, cone-shaped hallux epiphysis,
and syndactyly of the second and third digits are characteristic
findings in the extremities.

WAARDENBURG SYNDROME
• Also known as acrocephalosyndactyly type 4.
• Characterized by pigmentation abnormalities and
sensorineural hearing loss.
• At least six genes are involved in WS, including SOX10;
• Central myelin deficiency with cerebral and cerebellar
hypoplasia is seen
• Peripheral demyelinating neuropathy can result in
Hirschsprung disease.

GREIG SYNDROME
• Trigonocephaly with metopic or sagittal synostosis is a distinctive
presenting feature of GCPS.
• Pre- and postaxial polydactyly and cutaneous syndactyly of hands and
feet are common.
• Corpus callosal dysgenesis and mild cerebral ventriculomegaly are
recognized associations.

PFIEFFER SYNDROME
• Pfeiffer syndrome is formally known as acrocephalosyndactyly type 5.
• Multiple sutures are typically affected, and severe deformities such as
a "cloverleaf" skull are common

CARPENTER SYNDROME
• Carpenter syndrome is an autosomal-
recessive acrocephalopolysyndactyly.
• Craniosynostosis is a consistent and
severe component.
• As the name implies, both polydactyly
and syndactyly are often present.

THE DANDY-WALKER CONTINUUM (DWC)
spectrum of anomalies
1. Dandy-Walker malformation (DWM),
2. Vermian hypoplasia (VH),
3. Blake pouch cyst (BPC), and
4. Mega cisterna magna (MCM).

• Two measurements are important in
distinguishing these entities:
• (1) The Tegmento-vermian angle (the
angle formed by lines along the anterior
surface of the vermis and the dorsal
surface of the brainstem, normally < 18°)
and
• (2) The Fastigium-declive line (a line
drawn from the Fastigium— the dorsal
"point“ of the 4th ventricle on sagittal
images and the dorsal most point of the
vermis.

DANDY-WALKER MALFORMATION (DWM)
• Is a generalized disorder of mesenchymal development that affects both
the cerebellum and overlying meninges.

The most striking gross findings in DWM are
• (1) An enlarged posterior fossa
• (2) Upward displacement of the tentorium
and accompanying venous sinuses (Torcular
lambdoid inversion)
• (3) Cystic dilatation of the fourth ventricle.
• (4) Vermian abnormalities range from
complete absence to varying degrees of
hypoplasia.
• In DWM, the 4th ventricle choroid plexus is
absent.

VERMIAN HYPOPLASIA (VH)
Is part of the DWC spectrum.
• Superior rotation of the vermis,
• Increased tegmento-vermian angle (18-
45°), and
• Variable cerebellar hypoplasia
(diminished vermian volume below the
fastigium- declive line).
• The overall posterior fossa volume is
normal.

BLAKE POUCH CYST (BPC)
• It is an ependyma-lined protrusion of the fourth
ventricle through the foramen of Magendie into
the retrovermian cistern.
• The fourth ventricle choroid plexus is present but
displaced into the superior cyst wall.
• The tegmento-vermian angle is increased, but
the vermis is normal in size and configuration.
• The fourth ventricle has a "key hole" appearance.

MEGA CISTERNA MAGNA (MCM)
Is an enlarged retrocerebellar CSF collection (> 10
mm).
• There is no mass effect on the cerebellar
hemispheres or vermis.
• The vermis is normal as is the tegmento-vermian
angle (< 18°).
• Cerebellar veins and elements of the falx cerebelli
can be seen crossing through the MCS.

ARACHNOID CYST
• Not truly in the Dandy-Walker Continuum
• Cerebellopontine angle > Retro vermian
• No communication with 4th ventricle
• No crossing veins or falx cerebelli
• Causes mass effect

Associated Abnormalities
• Other CNS abnormalities are present in 70% of DWM.
• The most common finding is callosal agenesis or dysgenesis.
• A dorsal interhemispheric cyst may be present.
• Gray matter abnormalities (e.g., heterotopias, clefts, and pachy- and
polymicrogyria) are common associated abnormalities.

CRANIOVERTEBRAL
JUNCTION ANOMALIES
DR. KITTU
JUNIOR RESIDENT
DEPARTMENT OF RADIODIAGNOSIS
GOVT. STANLEY MEDICAL COLLEGE

The craniovertebral junction has a unique and complex anatomy .
• The occiput
• The first cervical vertebra or atlas
• The second cervical vertebra or axis
BONES

1. ATLANTO-OCCIPITAL JOINT
• Synovial joint formed between
occipital condyles and paired
superior articular surfaces on
the lateral masses of the atlas.
• ROM : flexion and extension
which allows the head to nod up
and down
2.ATLANTO AXIAL JOINT
• Complex of 3 synovial joints : paired
lateral atlantoaxial joint between the
lateral masses of C1 and C2, median
atlantoaxial joint between odontoid
process and posterior surface of the
anterior arch of atlas
• ROM : flexion, extension, axial rotation
and allows the head to move side to
side
• More dependent on ligaments for
stability and thus more prone for
instability in events of ligament
disruption.
JOINTS

1.ALAR LIGAMENTS
• Paired
• Arises from the posterior surface
of the dens and attaches the axis
to the skull base
2.TRANSVERSE LIGAMENT
• Arches behind the odontoid
process and attaches to the
medial surface of the lateral
masses of the atlas.
• Fixes the odontoid process firmly
to the posterior surface of the
anterior arch of the atlas
LIGAMENTS

3. CRUCIFOM LIGAMENT
Composed of transverse and vertical parts
Forms a cross behind the odontoid process
4. TECTORIAL MEMBRANE
Upward extension of the posterior
longitudinal ligament and runs posterior
to the cruciform ligament.
5. APICAL LIGAMENT
Extends from tip of the odontoid process
to the basion
6. LIGAMENTUM NUCHAE
Cephalic extension of the supraspinous ligament
Extends from spinous process of the C7 vertebra to inion of the occipital bone
7. ANTERIOR AND POSTERIOR ATLANTO – OCCIPITAL MEMBRANES

• Series of lines, angles and planes drawn to define the normal relationships
of the craniovertebral junction
Can be done in any imaging modality
• Some important angles include
1. Basal angle
2. Bull’s angle
3. Height index of Klaus
4. Boogard’s line and angle
• Some important lines include
1. Chamberlain’s line
2. Wackenheim’s clivus canal
line
3. Mc Gregor’s line(Basal line)
4. Mc Rae’s line(Foramen
magnum line)

Mc RAE’S LINE
• Line drawn between basion (anterior
margin of the foramen magnum) and
opisthion(posterior margin of the
foramen magnum)
• The inferior margin of the occipital
bone should lie at or below this line
• If the inferior margin of the occipital
bone lies above this line, it indicates
basilar impression

Mc GREGOR’S LINE
• Line drawn from the
posterosuperior margin of the
hard palate to the most inferior
surface of the occipital bone
• The tip of the odontoid process
should not lie above this line
>8mm in males and >10mm in
females
• Abnormally high odontoid process
indicative of basilar impression

CHAMBERLAIN’S LINE
• On lateral projection of skull base, a
line drawn from the posterior
margin of the hard palate to the
posterior margin of the foramen
magnum
• Tip of the odontoid process should
be within 3mm of this line
• >7mm above this line indicative of
basilar impression

DIGASTRIC LINE
• Line drawn between digastric grooves
on each side medial to the base of the
mastoid process
• The vertical distance from this line to
the odontoid apex and atlanto occipital
joint is measured
• The odontoid apex should not lie above
this line.

WELCKER’S BASILAR ANGLE
• In lateral projection of skull base, three
points are marked
1. Nasion (fronto nasal junction)
2. Center of the sella turcica(midpoint
between the clinoid processes)
3. Basion(anterior margin of the
foramen magnum)
• The normal angle varies between 123 to
152 degrees
• In platybasia, this angle becomes more
obtuse(>152 degree)

BOOGARD’S LINE AND ANGLE
BOOGARD’S LINE
• A line is drawn between nasion and opisthion
BOOGARD’S ANGLE
• A line is drawn connecting basion and
opisthion
• A second line is drawn from the dorsum
sellae to the basion along the plane of the
clivus
• In basilar impression, the basion will be
above the Boogard’s line and the angle will
be >135 degree

HEIGHT INDEX OF KLAUS
• A line is drawn from the tuberculum
sellae to the internal occipital
protuberance.
• The distance between this line and the
tip of the odontoid process is measured.
• It normally ranges between 30 – 40 mm
• Values < 30mm indicate basilar
impression.

ATLANTODENTAL INTERVAL
Distance between the anterior arch of
atlas and the odontoid process
• Normal values
1. Adults <3mm
2. Children < 5mm

BASION DENS INTERVAL
• Measured between the basion and
the tip of the odontoid process
• It is the distance from the most
inferior portion of the basion to the
closest point of the superior aspect
of the dens in the median
(midsagittal) plane
• Normal values
▪Radiograph <12mm
▪CT < 8.5mm

BASION AXIAL INTERVAL
• Distance between the basion and a line
drawn upward along the posterior
cortex of the axis
• Normally should be less than 12mm

POWERS RATIO
• Measurement of the relationship of the foramen
magnum to the atlas used in the diagnosis of atlanto
occipital dissociation injuries.
• Four points are marked :
• A – Basion
• B – Posterior spinolaminar line of the atlas
• C – Opisthion
• D – Anterior arch of atlas
• Two lines are drawn from A to B and C to D and distances
are measured
• Normally the ratio AB/CD should be less than 1
• Values > 1 indicate anterior atlanto occipital dissociation
injuries

PLATYBASIA:
• It is defined as abnormal flattening of the skull
base.
• Congenital : Down’s syndrome,
achondroplasia, cleidocranial dysostosis,
osteogenesis imperfecta, Chiari
malformations
• Acquired : Paget’s disease, rickets,
Osteomalacia, fibrous dysplasia, hypo and
hyperparathyroidism

BASILAR INVAGINATION
1. Congenital upward displacement of vertebral elements into a
normal foramen magnum with normal bone.
2. Causes stenosis of the foramen magnum and compression of the
medulla leading to neurological symptoms, obstructive
hydrocephalus or syringomyelia
3. Causes : Osteogenesis imperfecta, Klippel – Feil syndrome,
achondroplasia, chiari malformations, cleidocranial dysostosis

BASILAR IMPRESSION
1. It refers to secondary or acquired
form of basilar invagination due to
softening of the bones.
2. It is seen in conditions such as
rickets, osteomalacia, osteogenesis
imperfecta, Paget’s disease,
skeletal dysplasia, rheumatoid
arthritis and skull base infections

NORMAL VARIANTS
CONDYLUS TERTIUS
• Also called the third occipital condyle
• It is an ossified remnant at the caudal end of
the basiocciput
• Occurs due to failure of fusion of the fourth
occipital sclerotome.
• Radiologically differentiated from a fracture
by its well corticated margin and a typical
embryological location.

POSTERIOR RACHISCHISIS
• Absence of the posterior arch of
the atlas
• Majority occur in midline but
rarely can also occur in
posterolateral aspect
• The defect can be unilateral or
bilateral
• Bilateral posterior rachischisis
can mimic Jefferson’s fracture

ANTERIOR RACHISCHISIS
• Defect in the anterior arch of the
atlas
• Rare compared to posterior
rachischisis
• When associated with posterior
rachischisis, it is called as ‘split atlas’

PERSISTENT OSSICULUM TERMINALE
• The secondary ossification centre of the
odontoid process called as ‘terminal
ossicle’ normally fuses with the rest of
the odontoid process by 12 years of age.
• Persistence of the terminal ossicle
beyond 12 years of age is termed as
persisitent ossiculum terminale
• Differentiated from type 1 odontoid
fracture by its well corticated margins
and typical location

PONTICULUS POSTICUS
• Osseous roof along superior C1 arch covers C1 vertebral artery foramen
• Vertebral artery passes through osseous tunnel
• May be partial or complete
• Unilateral or bilateral

ASSIMILATION ANOMALIES
• C1 assimilation ("Occipitalized C1"): Segmentation failure
• Fibrous or osseous union between 1st spinal sclerotome and
4th occipital sclerotome

OS ODONTOIDEUM
• Rounded, corticated Os margins
• Dystopic or orthotopic Os position
• Orthotopic: Normal position with a
wide gap between C2 and Os
odontoideum
• Dystopic: Displaced
• Atlantoaxial instability more common
than with persistent ossiculum terminale.

SYNDROMIC CRANIOSYNOSTOSES
• Apert Syndrome
• Crouzon syndrome
• Saethre - Chotzen Syndrome
• Waardenburg Syndrome
• Greig Syndrome
• Pfieffer syndrome
• Carpenter syndrome

Craniosynostosis Chiari Dandy walker malformation

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