Abnormal Skull Shape

Felice D’ArcoDiagnostic Imaging

Great Ormond Street Hospital For Children

A Radiological Approach to Craniosynostosis

felice.d’arco@gosh.nhs.uk

Summary Normal Cranial Development: Anatomy

& Genetic Imaging Technique: How to do 3D CT,

when to do MRI, why do NOT do Plain Film

Imaging Patterns of Craniosynosinostosis: Pre- and Post-surgical

Associated Complications Pitfalls

Normal Cranial Development

Anatomy & Genetic

Single-Suture Synostosis - Defective dural-mesenchymal signaling issues- Thought to Be Idiopathic BUT genetic causes are increasingly

being identified- Minimal Complications/Associated Brain Abnormalities

Multi-Suture Synostosis - Genetic Factors Single Gene or Chromosomal Abnormalities- Iatrogenic Factors teratogens, early post-natal shunting of

hydrocephalus, early craniofacial irradiation for tumor control- Metabolic Diseases Mucopolysaccharidoses, I-Cell disease

(extremely rare!!)

Delay in sutural fusion - Hypothyrodism- Cleido-cranial dysostosis (RUNX2 mutation)- Zelweger Syndrome (peroxisomal disorder )

Blaser et al. Pediatr Radiol 2015

f: Anterior Fontanelg: Posterior Fontanel

b : Coronal Suture c : Sagittal Suture

d : Lambdoid Suture

 sphenoidal

fontanelSquamosal Suture

Mastoidfontanel

Spheno-Squamosal Suture

a : Metopic suture

Basioccipital bone

Exoccipitals bones

Supraoccipital bone (derived from cartilage)

Interparietal bone (derived from membrane)

Mendosal Suture

Shapiro and Robinson, Embryogenesis of The Human

Occipital Bone Am J Roentgenol 1976

1) Basioccipital Bone2) / 3) Exoccipital Bones4) Supraoccipital5) Interparietal

Mendosal Suture (arrows)

OPISTHION

BASION

Genetic of Craniosynostosis

Suture form at the site of meeting bone fronts Interdigitating fingers of bone project into the

suture Multiple genes govern this process through

osteoblast differentiation, apoptosis, osteogenesis etc…

Some genes are suture specific (e.g. TWIST1 along the frontal and parietal edge) some are not.

Genes Involved in Syndromic Craniosynostosis : FGFR1-3, TWIST1, MSX2, RAB23

Some single-suture non-syndromic synostoses have been found to have genetic causes (Sagittal: WDR35, BBS9, BMP2; FREM1, Cr9p del: Metopic)

Phenotypic and Genetic Veriability

FGFR1-3

Pfeifer S.

Crouzon S.

Apert S.

from internet

Phenotypic and Genetic Veriability

MSX2Saethre-Chotzen

S.

One coronal + sagittal

Two coronal + sagittal

All the syndromic craniosynostosis may progress

to cloverleaf skull deformity

Imaging technique Clinical Observation: 93% concordance

with 3D CT Radiography: Not Longer Indicated CT low dose with 3D reformats MRI Brain Abnormalities (in complex

syndromic craniosynostoses) CTV and MRV sinovenous thrombosis

(in complex syndromic craniosynostoses)

3D CT Dx with mimics: Positional Plagiocephaly,

Fractures

Unsuspected additional sutural stenosis

Pre-operative planning

Very Low Dose 3D CT dose : 40.00 DLP mGy-cm Unenhanced head CT: 285.00 DLP Average dose reduction: 85%

How to Scan a 3D Head CT

Branson HM 2011

True Axial Plane (parallel to the hard palate) From the bottom of the chin to the top of the

head Helical scan: kV 80, mA 60, rotation 0.5 sec

(MAS of 30). Slice thickness: 0.625 mm, pitch 0.969:1, table speed: 19.37 mm/rotation

Scan on Bone Window (this is not a scan for the brain parenchyma)

3D reconstruction: different projections

Branson HM 2011

How to Report a 3D Head CT Look at the axial images for gross

ventriculomegaly, hemorrhages, calcifications, copper beaten skull (raised intracranial pressure?)

How to Report a 3D Head CT

Document Head Shape (brachycephaly, scaphocephaly, turricephaly)

Look for orbit and facial bone symmetry Individually look at each suture: ? Absence ?

Ridging ?Sclerosis ? Partial Fusion Skull Base and CVJ

Head Shape General Rule: The head grows where there is

space!

- Metopic Synostosis: Trigonocephaly

- Sagittal Synostosis: Scaphocephaly

- Mono-coronal Synostosis: Ant Plagiogephaly

- Mono-Lambdoid Synostosi: Post Plagiocephaly

- Bi-coronal Synostosis: Brachycephaly

Specific Imaging Patterns in

Craniosynostoses

Lambdoid Synostosis ?

The left lambdoid suture is patent and anterior to the right The long axis of the left IAC is anterior to the right Ispilateral frontal bossing Absent mastoid “bump” Parallelogram configuration of the skull on axial view

Left LeftLeft

POSITIONAL PLAGIOCEPHALY

Positional Plagiocephaly Most common cause of abnormal skull

shape in infant (recommended protocol of back/side positioning during sleep to decrease infant cot death)

Kadom and Sze AJR:194, March 2010

Ispilateral frontal bossing

Parallelogram configuration of the skull on axial view

Lambdoid Synostosis

Controlateral Posterior Bossing and

trapezoid shapeAbsent Suture on the

Right Mastoid Bump and absent suture on the

right

L

Long axis of the left IAC

Positional Plagiocephaly

Right Lambdoid Synostosis

Lambdoid Synostosis Unilateral Lambdoid Synostosis is rare

5 % of isolated non-syndromal craniosynostosis

Bilateral Non-Syndromic is extremely rare marker of underlying Rhomboencephalosynapsis (suggest MRI)

Bilateral Syndromic Apert and Pfeiffer Syndromes

Blaser et al. Pediatr Radiol 2015

Sagittal Synostosis Most common craniosynostosis (40-60%) Scaphocephaly Familial cases with AD transmission (6) Males ++ (role of androgens in sutural

osteogenesis) Multiple Births / Uterine malformations +

+ (intrauterine head constraint)

Abnormal Skull Shape Pediatr Radiol 2008 38 (suppl 3):488-496

internet

9 y

?

Age of Fusion

Metopic Suture: 3 months – 2 years Lambdoid, Sagittal and Coronal : 40

years Squamosal: 40 to 70 years Fontanelle:

Posterior: 2-3 months Sphenoidal: 6 months Mastoid: 6-18 months Anterior: 1-3 years

Fused vs Narrowed Sutures

Sagittal Coronal

Mitchell et al. AJNR 32:1801– 05 2011

• Suture widths sagittal and coronal sutures at zero months of age were 5.0 and 2.5 mm, respectively

•From zero to 1 month of age, these suturesnarrowed significantly to 2.4 and 1.3 mm, respectively.

•From 1 to 12 months of age, sutures narrowed gradually.

Metopic Synostosis Was thought to be rare (10% of CS),

however recent studies suggest increasing incidence, making it the second most frequent CS

Normal closure 3 months – 2 years Can be diagnosed in utero

(trigonocephaly) 1/3 syndromomic: Jacobsen/11q23

selection, Cr 9p deletion Brain malformations are common and

should be excluded (microcephaly, holoprosencephaly, atrophy) Lee HQ et al. J Craniofac Surg 2012

1) Narrowed anterior cranial fossa width (trigonocephaly)2) Ethmoidal hypoplasia3) Hypotelorism 4) Upward deviation of the medial orbit rim (“quizzical” orbit)5) Bony ridge (can be normal!!!)

8 months

The Fact that the Metopic S is closed at 8 months is not enough for the diagnosis of Metopic CS

1) The earliest evidence of metopic suture closure was at 3 months, the age at which 33% of patients were closed.

2) At 5 months of age, 59% of sutures were closed.

3) At 7 months of age, 65% were closed.

4) At 9 months of age, 100% were closed.

5) Evidence of metopic suture fusion before 2 years of age should not be used as criteria for metopic synostosis surgery (clinical diagnosis).

6) Diagnosis is Clinical

Prenatal trigonocephaly due tometopic synostosis is seen in a 29-week fetus with trisomy 13 (Blaser 2008)

Prenatal trigonocephaly due in a 26-week fetus with valproate syndrome (Meizner 1993)

Genetic and Toxic causes of Metopic Synostosis

Coronal Synostosis Female +++

Brachycephaly + Complicated effect on craniofacial appearance

Associated Skull Base involvement and fronto-sphenoidal synostosis

Harlequin Deformity (superior elevation of the lesser wing of the sphenoid)

Unilateral Synostosis: some genes are implicated (e.g. FGFR3, TWIST1)

Bilateral Synostosis: Apert, Crouzon, Muenke, Pfeifer etc. Multisutural involvement frequent Progressive Pansynostosis (cloverleaf

deformity)

Blaser et al. Pediatr Radiol 2008

Unilateral Coronal Synostosis

- Harlequin Orbit

-Retrusion of the lateral/upper margin of the orbit

- Nasal tilting

- Crooked Aspect of the Normal Coronal Suture

by Khamykc-Blackout

Combined Unilateral Coronal and Lambdoid

Synostosis

- Harlequin Orbit

- Masotid Bump

- Angled Skull Base

Blaser et al. Pediatr Radiol 2015

Non-syndromic Bilateral Coronal

Synostosis

- The other sutures are normal

- Harlequin less accentuated

because of patent fronto-sphenoidal

- Brachycephaly

- Normal skull base

-Exorbitism (shallow orbits)

6 months

Syndromic Craniosynostosis TRIAD: Bicoronal Synostosis + FGFR mutations +

Associated Extremity Malformations

Often other synostoses are associated (++ skull base) Occasionally progression to pansynostosis and cloverleaf skull deformity

APERT: FGFR2 mut + hands/feet syndactyly + bilateral coronal craniosynostosis + involvement of posterior fossa sutures

CROUZON: FGFR2/3 mut + ear malformations + short humerus/femur + hypoplastic maxilla + bilateral coronal craniosynostosis + involvement of posterior fossa sutures

PFEIFER: FGFR1/2 mut + broad first digit of hands and feet +dental problems + hearing loss + bilateral coronal craniosynostosis + involvement of posterior fossa sutures

Known association with brain abnormalities (MRI brain!)

4 day-old, Apert Syndrome

7 y, Crouzon Syndrome with pansynostosis

Wikipaedia

Indian J Radiol Imaging. 2011 Jan-Mar; 21(1): 49–56.

Radiol Bras. 2014 May-Jun; 47(3): 189–190.

Cloverleaf deformity (Kleeblattschadel)

Other Patterns Z-Pattern: craniosynostosis involving the left coronal,

sagittal, and right lambdoid sutures . (Schmelzer and Fearon 2007)

Mercedes-Benz Pattern: Bilateral lambdoid and sagittal sinostosis. (Rhodes, Kolar and Fearon 2010)

Post-operative Imaging of Craniosynostosis

1) Calvarial Vault Remodeling : traditional surgery, old children (> 6 months)

Can be endoscopic in children < 6 months

Post-operative Imaging of Craniosynostosis

2) Spring-mediated cranial reshaping

Complications Hydrocephalus: Rare in unilateral

synostosis, 40% in syndromic synostosis* Pathogenesis: hypoplastic PF and venous

outlet occlusion with consequent ICP (CTV, MRV)

Chiari I and Syringomyelia

*Childs Nerv Syst (2005) 21: 902–912

Pediatr Radiol 2008, 38:S488-496

Crouzon syndrome: bilateral jugular vein stenosis andprofuse extracranial venous collaterals

Complications: Post-Operative

Hemorrhage CSF leaks Sinovenous damage Thrombosis Restenosis (15-89% but only few cases

require reoperation for ICP)

Associated Brain Abnormalities Metopic Synostosis: Microcephaly,

Holoprosencephaly, Atrophy (Faro 2006) Bilateral Lambdoid Synostosis:

Rhombencephalosynapsis (de Mattos 2014)

Rhombencephalosynapsis in a child with Gómez-López-Hernández syndrome and bilateral Lambdoid synostosis (De Mattos Pediatr Neurol 2014)

Skull fracture vs. accessory sutures: how can we tellthe difference?

Emerg Radiol (2010) 17:413–418

Accessory Sutures in Parietal and Occipital Bones (multiple ossification centers)

Accessory Suture: incomplete union of two ossification centers

Parietal Bone: 2 ossification centers (accessory intraparietal or subsagittal suture)

Occipital bone: 6 ossification centers (mendosal suture, midline occipital fissure)

Emerg Radiol (2010) 17:413–418

Accessory Intraparietal or Subsagittal Suture

Midline occipital Fissure and Mendosal Sutures

Radiographic differentiation of skull fractureand accessory suture

FRACTURE: -sharp, non-sclerotic edges-widening of the fracture as it approaches the suture-associated sutural diastasis-high impact fractures can cross the suture- often unilateral

ACCESSORY SUTURE: -zigzag pattern, sclerotic borders-no changes in the adjacent suture-they join the suture-often bilateral

fracture

suture

Emerg Radiol (2010) 17:413–418

Conclusion Knowledge of normal anatomy and

embriology is critical in the radiological evaluation of craniosynostosis and DDX between accessory sutures and fractures

Low dose CT with 3D reformats is the Gold Standard

In case of multiple craniosynostosis (bicoronal +++) suggest syndromic condition and MRI/CTV for associated complications