Thorsang Chayovan and Chaiyapongse TangsittitumJune 01, 2016

Normal brain development

Dorsal induction

(neural tube formation & dysjunction)

Ventral induction

(vesicle formation & cleavage)

Cortico-genesis

(histogenesis & migration)

Proliferation

Migration

Organization

Myelination

2.66: 1000 births Mechanism: genetic, intrauterine

environment

60% unknown cause

20% inherited disease

10% chromosome

10% environment Most common: anencephaly, spina bifida

Congenital brain malformations

Disorders of dorsal induction

Neural tube defects

Anencepahly

Cranial dysraphism

(cephalocele)

Chiarimalformation

Disorders of ventral induction

holo-prosencephaly

Alobar

Semilobar

Lobar

Septo-optic dysplasia

Dandy Walker spectrum

Corpus callosumagenesis

Disorders of

Cortico-genesis

Proliferation

Migration

Organization

Myelination

Disorders

Hypo-myelination

Dys--myelination

Result in defects of closure

Anencephaly

Encephaloceles

Chiari malformations

Spinal dysraphism

Absence of the cranial vault, cerebral hemispheres, and diencephalic structures.

1: 1000 births

Acrania: no skull + normal brain tissue

Excencephaly: no skull + amorphous brain

Anencephaly: no skull + no brain

Acrania anencephaly sequence

Antenatal USG(detectable at 11 wks, 100% accuracy at 14 wks)

No brain tissue above orbits

Absent calvarium(may found parts of occipital bone and mid brain)

Exencephaly: have small amount of neural tissue

Low CRL

"frog eye" or "mickey mouse" appearance

Polyhydramnios

Defect in skull and dura with extracranialextension of intracranial structures

Most common in midline Causes: several

Failure of neurulation

Herniation after neurulation

Failure induction of bone

Failure of basilar ossification center to unite

Cephaloceles

Meningo-cele

CSF

Meningo-encephalocele

CSF

BRAIN(dysgentic &

nonfunctioning)

Meningo-encephalo-cystocele

CSF

BRAIN

VENTRICLES

Atreticcephalocele

Fibro-fatty tissue

Gliocele

CSF

Glial tissue

Pathological classification

(based on the contents of the sac)

Cephaloceles

Occipital ParietalFronto-

ethmoidalTrans-

sphenoidalNasal

Anatomical classification

(based on the location of the defect)

3 subtype Frontonasal: between frontal and nasal bones

Frontal bone displace superiorly Nasoethmoidal: between nasal bone and nasal

cartilage Nasal cartilage, nasal septum nd wthmoid bone

displace posteroinferiorly Nasoorbital: in bony canal at medial wall of orbit

between maxilla and lacrimal/ethmoid bone Frontal process of maxilla displace anteromedially Lacrimal and lamina papyracea displace posterolaterlly

Cephalocele connect with intracranial cavity via a strand of connective tissue

Defect from persistent of midline neural crest cell that prevent normal induction or ectoderm and mesoderm

Parietal: poor prognosis; associated with porencephaly, interhemispheric cyst, callosalagenesis, venous anomaly Small, hairless midline mass near the vertex

Occipital: good prognosis, low associated brain anomaly Small mass just above external occipital

protuberance, enter the calvarium via a defect and penetrate the dura below the torcular and terminate at falx or tentorium

Hindbrain anomaly which cerebellum descends into cervical canal

Congenital tosillar ectopia Elongated, peg-like, cerebellar tonsil and

displaced inferiorly through the foramen magnum into upper cervical spinal canal

Normal vermis, 4th ventricle and medulla

Association

Cord(20-40%): hydromyelia/ syringomyelia

Bone(25%): atlantooccipital assimilation, platybasia, basilar invagination, fused cervical vertebrae(Klippel-Feil)

Complex malformation involving skull, dura, brain, spine, and spinal cord

Unknown etiology Multiple abnormalities

Skull and dura

Hindbrain, cerebellum, and midbrain

CSF space

Cerebral hemisphere

Spine and spinal cord

Skull and dura Lacunar skull: scooping-out appearance

Scalloping and thinning of the inner calvarial table

Small and shallow posterior fossa with low-lying transverse sinuses and torcular herophili

Large foramen magnum(gapping)

Concave posterior aspect of petrous temporal bones

Short, concave clivus

Dysplastic falx cerebri and dural fold

Heart-shaped incisura

Skull and dura(cont)

Thinned, hypoplastic, or denestrated falx

Irregular serrated interhemispheric fissure

Hindbrain, cerebellum and midbrain

Downward medulla and cerebellum into upper cervical canal

Medullary kink or spur(70%)

Ectopic choroid plexus from 4th ventricle

Towering cerebellum(upward herniation)

Cerebellum wrap around the brainstem

Pointed or beaked tectal plate

CSF space(90%)

Small, elongated, caudally displaced 4th ventricle

Large 3rd ventricle and prominent massa intermedia

Normal to enlarged lateral ventricle

Colpocephaly

Serrated or scalloped margins of lateral ventricles

Frontal horns point anteroinferiorly

Aqueductal stenosis

Small cisterna magna

Cerebral hemisphere

Sulcation and gyration disorder e.g. polymicrogyria, heterotopia, stenogyria, corpus callosal dysgenesis

Spine and spinal cord

Myelomeningocele(all cases)

Syringohydromyelia

Diastimatomyelia

Lipomyelomeningocele(uncommon)

Small posterior fossa Caudally displaced brainstem Low occipital or upper cervical bony defect

with herniation of posterior fossa content

Severe cerebellar hypoplasia without displacement of the cerebellum through the foramen magnum

Chiari V malformation

Absent cerebellum

Herniation of the occipital lobe through the foramen magnum

Chiari 0 malformation

Syrinx

No cerebellar tonsil or brain stem descent

Anterior commissure, hippocampalcommissure, corpus callosum(largest)

Development: anterior commissure→hippocampal commissure→ corpus callosum

Genu→ body → splenium→ rostrum(last) If anomaly occurs in which part, the part

formed later will absent(except in destructive causes and holoprocencephaly)

Primary agenesis: never forms Secondary dysgenesis: forms normally and

subsequently destroyed

Often associated with anomalies of cerebrum and cerebellum

Chiari II: most common

Dandy-Walker malformation

Anomalies of neuronal migration and organization

Encephalocele

Midline facial anomaly

Aicardi syndrome

Fetal alcohol syndrome

Genetic association

Apert syndrome

CRASH syndrome

DiGeorge syndrome

Williams syndrome

Fragile X syndrome

Morning glory syndrome

CT

Axial: parallel lateral ventricle(racing car sign)

Coronal: anterior horns resemble viking helmet, moose head or texas longhorn

Colpocephaly(axial: teardrop configuration)

Pointed frontal horns

± midline cyst or lipoma

MRI T1w Sagittal

Gyri radiate out from 3rd ventricle

Everted cingulate gyrus, absent cingulate sulcus Coronal

Longhorn-shaped anterior horns

Elongated foramina of Monro

Keyhole temporal horn and vertical hippocampi

Ventriculomegaly(type I interhemispheric cyst varient)

MRI T2w Colpocephaly Probst bundle: hypointense like internal

capsule and anterior commissureMRA ACAs “meander”, no CC genu or curve around ± azygous ACA

US Coronal

Absent corpus callosum

Trident lateral ventricle

Wide lateral ventricle, colpocephaly

Sagittal

Radially arranged gyri pointed to 3rd ventricle

Type I: interhemispheric cyst as a diverticulum of ventricular system

Type 2: not connect with ventricular system

Fused 2 hemisphere

Holoprocencephaly

Septo-optic dysplasia

Midline hemisphere fusion Failure of normal prosencephalic cleavage 1:13000 live births Materal DM, rubella, toxoplasmosis, syphillis,

fetal alcohol syndrome, trisomy(13, 15, 17, 18), triploidy

4 forms Alobar Semilobar Lobar Syntelencephaly

Finding alobar semilobar lobar

Craniofacial anomaly

severe variable absent of mild

Ventricles monoventricle rudimentary occipital horn

squared-off frontal horns

Septum pellucidum

absent absent absent

Falx cerebri absent partial well-formed

Interhemisphericfissure

absent partial present(some anterior fusion)

Basal ganglia, thalami

fused partially separated

separated

2 major findings

Hypoplasia of optic nerve

Hypoplasia or absent septum pellucidum

2/3 have hypothalamic-pituitary dysfunction

Growth retardation

Presentation: nystagmus, diminish visual acuity, hypotelorism

Imaging

Hypoplasia or complete absence of septum pellucidum→ box-like frontal horns

Hypoplasia of optic nerve(50%) ± optic canal

Bulbous dilatation of anterior recess of 3rd

ventricle(from hypoplasia of optic chiasm and hypothalamus)

Lissencephaly (agyria) Pachygyria Heterotopia Polymicrogyria Schizencephaly

Migration disorders

Under-migration

Classic lissencephaly

(type I)

Over-migration

Cobble stone lissencephaly

(type II)

Ectopic migration

Heterotopia

Subependymal

Subcortical

Band heterotopia

Category Types

Classic (or Type 1) lissencephaly

•LIS1: lissencephaly due to PAFAH1B1 mutation

• type 1 isolated lissencephaly• Miller-Dieker syndrome

•XLIS: lissencephaly due to doublecortin(DCX) mutation•lissencephaly, type 1, isolated

Cobblestone (or Type 2) lissencephaly•Walker-Warburg syndrome•Fukuyama syndrome•Muscle-eye-brain disease

Other types

•LIS2: Norman-Robert syndrome (RELN mutation)•LIS3: TUBA1A•LISX2: ARX•Microlissencephaly

Complete—Agyria Incomplete—Pachygyria-agyria

Type I: Classic Agyria/pachygyria Thick inner band GM Cell sparse WM zone ↓T1↑T2 Thin outer layer GM Shallow sylvian fissure;

hourglass cerebrum CC/SP agenesis/hypoplasia LIS1: parietal/occipital XLIS(DCX):

subfrontal/temporal

Classic lissencephaly

Premature brains (up to 26 wks)

Smooth

Mimic lissencephaly

Microcephaly with simplified gyral pattern

Brain ≥ 3 standard deviations below normal

Pachygyria

More localized, often multifocal, and usually asymmetric

Indistinct GM-WM junction

Arrested neuronal migration with ectopic gray-matter nodules or band-like areas

Periventricular germinal zone to cortex Often asymptomatic but can be seizure focus Must distinguish from tumor Temporal and occipital horns Congenital Acquired e.g. maternal trauma, infection,

toxin

Multiple small nodules/bands

Periventricular germinal zone to cortex

Match gray-matter signal

Lack enhancement Lack calcification Margin maybe indistinct Mass-like; mimic tumor

Subependymalheterotopia

Double cortex

Thick deep to thin >> seizure risk

90% in girls

Thin and dysplastic overlying cortex

Associated anomalies

Zellweger syndrome

▪ Peroxisomal disorder

▪ Abnormal migration, hypomyelination, band heterotopia

Agenesis CC

Chiari 2 malformations

Dandy-Walker spectrum

Organization disorders

Superficial cortex

Focal cortical dysplasia

without Balloon cells

Whole cortex

Polymicrogyria Schizencephaly

Cortical dysplasia Irregular cortex with numerous small

convolutions and shallow or obliterated sulci Late migration and organization: Unequal

distribution of final migrating neurons (at GA 20-24 wks)

Derangement of six layered lamination of cortex

2 patterns by degree of myelination: <12 months: thin, small, fine undulating cortex

with normal thickness (2-3 mm)

>18 months: thick, bumpy cortex (5-8 mm), hypomyelination, cortical infolding

Irregular, indistinct outer and inner cortical surfaces

Shallow/flat sulci Small, isolated, unilateral to bilateral Predilection for perisylvian regions

Thickened cortex with nodular surfaces and irregular gray-white matter interfaces

Polymicrogyria

Split brain Clefts in cerebral hemispheres-

ventricle/subarachnoid space lined by gray matter

Causes Destructive vascular lesions (e.g., MCA occlusion) Infections (e.g. TORCH) before 28 fetal wks

Up to half are bilateral Location: Frontal/parietal Associated with absent septi pellucidi (70%),

dysgenesis of CC and heterotopia

Type I = closed lips

Absent CSF cavity

Type II = open lips

Clefts filled with CSF

Communication of extraaxial fluid-ventricle at cleft site

• Cerebral clefts lined with gray matter extending from cortex to ventricle

• CSF within clefts

Schizencephaly

Dandy Walker spectrum

Dandy Walker malformation

Dandy Walker variant

Persistent Blake’s pouch

Mega cisternamagna

DWM DWV Persistent Blake’s pouch

Mega cisternamagna

Anterior membranous area anomaly Posterior membranous area anomaly

Retro-cerebellar cyst

Large posterior fossa High-inserting venous

confluence Large posterior fossa

cyst extending dorsally from fourth ventricle

Vermianaplasia/hypoplasia

+-Hydrocephalus 80%

More common Smaller

retrocerebellar cyst Milder vermian

agenesis Normal-sized

posterior fossa Normal brainstem

DDx for normal-sized posterior fossawith cystic collection

Retrocerebellar arachnoid cyst Giant cisterna magna Dandy-Walker variant

Ependyma-lined protrusion of fourth ventricle through foramen of Magendieinto retrovermiancistern

Displaced fourth ventricle choroid plexus

Increased tegmentovermianangle

Normal-sized vermisand configuration

http://roentgenrayreader.blogspot.com/2010/04/tegmento-vermian-angle.html

Large posterior fossa Normal fourth

ventricle, vermis, and supratentorialbrain

Mildest DWS

DWM DWV PersistentBlake’s pouch

Mega cisternamagna

Vermis Hypo-plasticRotated upwards

Hypo-plastic No or mild hypoplasia

No or mild hypoplasia

4th ventricle Markedly dilated Dilated Dilated Normal

Posterior fossa Expanded Normal size Normal size Expanded

hydrocephalus 75 % of cases 25% of cases Present No

Destructive lesions

Hydranencephaly Porencephaly

Formed brain tissue destruction

CSF cavity communicates with ventricular system

Etiology: probably acquired

Vascular/infectious in utero

Destruction of cerebral hemisphere

Extreme form of porencephaly

Caused by bilateral ICA occlusion

Replaced by CSF-filled sacs Preserved thalami, brainstem, posterior

fossa (posterior circulation) Must differentiate from hydrocephalus

Fluid-filled cranial vault above tentorium No supratentorial cortical tissue

Osborn's Brain: Imaging, Pathology, and Anatomy Diagnostic Neuroradiology: A Text/Atlas Anne G.

Osborn Grainger & Allison's Diagnostic Radiology Pediatric Neuroimaging A. James Barkovich MD

and Charles Raybaud MD Diagnostic Imaging: Pediatric Neuroradiology

A Barkovich http://www.slideshare.net/hytham_nafady/congenital

-brain-malformations/35 http://roentgenrayreader.blogspot.com/2010/04/teg

mento-vermian-angle.html

Which one is primary neurulationabnormality?

Chiari I

Chiari II

Holoprocencephaly

Hydranencephaly

Syntelencephaly

Chiari, false?

Meningoencephalocele almost always associated with Chiari II

Myelomeningocele associated with Chiari I

Syringohydromyelia associated with Chiari II

Chiari III = Chiari II+exernal brain herniation into cephalocele

Chiari I, sagittal spine is necessary

Dandy-Walker malformation, false?

Torcular and transverse sinus >> superior displacement

Cystic dilatation of fourth ventricle

Small posterior fossa