Imaging in developmental malformations of the brain

Imaging in Developmental Malformations of the Brain

Presenter :Dr.Chakradhar

Over view1.Introduction2.Normal development of Brain3.Classification of malformations4.Imaging features of anomalies5.conclusion

Imaging in developmental Malformations of the brain

Introduction

Congenital anomalies of the brain Extremely complex Best studied by correlating with embryological

development.

Imaging in developmental Malformations of the brain

NORMAL BRAIN DEVELOPMENT

MYELINATIONDORSAL INDUCTIONFormation of neural

VENTRAL INDUCTIONFormation of vesicles

and SegmentationMYGRATION, andPROLIFERATION

a.Primary Neurulation

b.Secondary neurulation

Imaging in Developmental malformations of the brain

Stages of brain development

Three phases: Neurulation, Canalization, Retrogressive differentiation

Stage 1: Dorsal Induction: Formation and closure of the neural tube

Occurs at 3-5 weeks

Dorsal induction defects:

Neural tube defects -Anencephaly, -Cephalocele, - Chiari malformations and -Spinal dysraphic disorders

Stage 2: Ventral Induction: Formation of the brain segments and face

Occurs at 5-10 weeks of gestation

Stages of brain developmentImaging in Developmental malformations of the brain

Three vesiclesProsencephalon - cerebral hemispheres/thalamus, Mesencephalon- midbrain and Rombencephalon- cerebellum/brain stem

Ventral induction disorders:

Holoprosencephalies, Dandy Walker malformation, Cerebellar hypoplasia/dysplasia Joubert syndrome, Rhombencephalosynapsis, Septo -optic dysplasia, and Facial anomalies.

Stage 3: Migration and Differentiation Occurs at 2-5 months of gestation

Neuronal migration from germinal matrix to the surface resulting in Cortical organization

Migration Disorders:

Heterotopias, Agyria-pachygyria, Polymicrogyria, Lissencephaly, Schzencephaly, Corpus callosal agenesis, Lhermitte-Duclos disease

Differentiation and proliferation disorders:

Aqueductal stenosis, Arachnoid cyst, Megalencephaly, Micoencephaly, Neurocutaneous syndrome (phakomatoses)Congenital vascular malformation, andCongenital neoplasms

Stage 4: MyelinationBegins at 6 months of gestation, Matures by 3 years.

Progresses from Caudal to Cephalic, Dorsal to Ventral, and Central to Peripheral

Disorders of Myelination Dysmyelinating diseases, Leukodystrophies.

DISORDERS OF NEURAL TUBE FORMATION

DISORDERS OF SEGMENTATION

DISORDERS OF MYGRATION and

CORTICAL ORGANISATION

DISORDERS OF MYELINATION

a.Anencephaly

b.Cephaloceles

c.Chiari Malformations

a.Holoprosencephaly1.Alobar

2.Semilobar 3.Lobar

b.Corpus callosal agenesis

c.Dandy Walker malformations

a.Hetrotropias

b.Lissencephaly, Schizencephaly

Classification of congenital malformation of brain

a.Leukodystrophies

b.Dysmyelinating Disorders

Neural Tube Defects

Anencephaly Neural Tube Defects

complete or partial absence of the cerebral structures, cranial vault and skull base.

It results from failure of closure of the cephalic portion of the neural tube

CephalocelesHerniation of intra cranial structures through

congenital defects in Dura and skull

Cephaloceles

MeningoencephalocystoceleMeningoencephaloceleMeningocele

MeningesMeninges Meninges

Neural tissue Neural tissue

Ventricles

Neural Tube DefectsImaging in Developmental malformations of the brain

Neural Tube Defects

Encephalocele

Fronto Nasal Encephalocele Occipital Encephalocele

Neural Tube Defects

Herniation of brain and Meninges through a defect in the skull.It is typically covered by skin (closed defect) or a Thin layer of epithelium (open defect).

Fronoto Nasal, Naso Orbital Encephalocele

Nasal Glioma(D/d for encephaloele)

Neural Tube Defects

Type of Chiari malformation

Imaging features(core) Associated findings

Type 1 (Tonsillar Ectopia)

Elongated cerebellar tonsils with herniation into cervical canal

Syringohydromyelia(30-60%)

Type 2 (Arnold Chiari)

Herniation of vermis ,tonsils, medulla 1.Small and shallow posterior fossa2.Myelomeningocele (nearly 100%)3.Upward herniation of cerebellar hemispheres 4.Corpus callosal dysgenesis, heterotopias, polymicrogyria

Type 3 Type 2 + occiputal encephalocele

Type 4 Cerebellar Aplasia/Sever Hypoplasia

The chiari malformations

Neural Tube Defects

Chiari I Malformation

Neural Tube Defects

Level below the Foramen Magnum First Decade: 6mm Second /Third decade: 5mm Fourth-Eight Decade:4mm and Nienth Decade:3mm

Chiari II Malformation

Neural Tube Defects

Disorders of Diverticulation and Segmentation

Holoprosencephaly

Cerebellum and brain stem are relatively normal

Developing Forebrain (prosencephalon) fails to divide into hemispheres and lobes.

Normal brain Alobar Holoprosencephaly

semilobar Holoprosencephaly Lobar Holoprosencephaly

Types of Holoprosencephaly

Alobar Holoposencephaly

• Single cresent shaped ventricle • No Separation of the cerebral hemispheres• Fused thalami and basal ganglia• Absence of septum pellucidum, corpus callosum, falx cerebri, and interhemispheric fissure

Semilobar holoprosencephaly

• Interhemispheric fissure is formed posteriorly•Rudimentary occipital and temporal horns•Thalami and basal ganglia are partially separated•Septum pellucidum is absent• callosal splenium may be formed

Lobar holoprosencephaly

• Ventral portions of the frontal lobes remains fused• Rudimentary frontal horns are formed • Septum Pellucidum is absent• Thalami and basal ganglia well separated

Septo optic Dysplasia (de Morsier syndrome)

• Milder form of lobar holoprosencephaly• Hypoplastic optic nerves, optic chiasma, • Absent septum pellucidum•Squared frontal horns

Associated hypoplasia of Hypothalamic-Pituitary axis seen in 2/3rd cases

Imaging in Developmental malformations of the brainDisorders of Diverticulation and Segmentation

Corpus Callosum Agenesis

Corpus callosal development starts at 12 weeks , and completes by 20 weeks

Formation is from anterior to posterior direction, Starts with Genu- Body-Splenium. The rostrum is last to develop

Corpus Callosum Agenesis

Complete agenesis Partial agenesis

Complete callosal agenesis

•Entire corpus callosum, cingulate gyrus and sulcus are absent•Widely separated, parallel and non-converging lateral ventricles.• Colpocephaly (dilated occipital horns) •Frontal horns are small and pointed

Complete corpus callosal agenesiscolpocephaly

Disorders of Diverticulation and Segemtation

Partial callosal agenesis

•Splenium and rostrum absent• Genu and body present

Associated anomalies•Migration disorders (heterotopias, lissencephaly, schizencephaly)• Chiari II malformation• Dandy-Walker malformation• Holoprosencephaly• Corpus callosal lipoma

Disorders of Diverticulation and Segmentation of Posterior fossa

Dandy walker spectrum

Dandy Walker syndrome

Dandy Walker variant

Mega Cysterna Magna

Imaging in Developmental malformations of the brainDisorders of Diverticulation and Segmentation of Posterior fossa

Joubert’s Syndrome (Congenital Vermian Hypoplasia)

• Vermian dysgenesis•Enlarged superior cerebellar peduncles and • High riding fourth ventricle.

Associated anomalies• Occipital encephalocele (30%),• Callosal dysgenesis,• Cortical dysplasia,• Hypothalamic hamartoma, and• Ocular, hepatic & renal diseases.

Disorders of Diverticulation and Segmentation of Posterior fossa

Classified into two groups:

Pontocerebellar hypoplasia (PCH).• Combined hypoplasia of both the cerebellum and the pons•These are primarily genetic disorders

• Hypoplastic Brain stem and cerebellum that is close to the tentorium• Cerebellar hemisphares are wing like, appear to float in posterior fossa.

Differentials of pontocerebellar hypoplasia

CDG syndromes-(disialotransferrin) will be elevated in CDGDandy-Walker syndrome - Normal PonsDandy-Walker variant -Normal Pons

Disorders of Migration

Ectopic Migration

Cobble stone-Lissencephaly(type 2)

Over Migration

Classic Lissencephaly (type1)

Under Migration

Migration Disorders

Band Heterotropia

Subcortical

Subependymal

Heterotrpia

Lissencephaly (Agyria-Pachygyria):

Refers to “smooth brain” with absent or poor sulcation.

Types: Complete (agyria) Incomplete (pachygyria).

• Thickened cortex with flat broad gyri•Smooth gray-white matter Interface• Colpocephaly Oblique and shallow • Sylvian fissures- figure eight

Type I (classical) Lissencephaly

Associated with Miller-Dieker syndrome

Type II(Cobblestone) Lissencephaly

• Thickened cortex • Polymicrogyric appearance. • Hypomyelination of underlying white matter

Associated with Fukuyama congenital muscular dystrophy,Walker-Warburg syndrome and muscle-eye-brain syndrome

Two types: Nodular type(common), Band/laminar type (uncommon)

HeterotopiasPresence of normal neurons at abnormal sites

Best appreciated on medium tau inversion recovery sequences

Nodular type:

• A layer of neurons interposed between the ventricle and cortex•Overlying cortex has pachygyria or polymicrogyria

Band or laminar type

Disorders of Cortical organisation

Non lissencephalic Cortical Dysplasia

Disorders of Cortical organisationImaging in Developmental malformations of the brain

Polymicrogyria

• Thickened cortex •Irregular, bumpy gyral pattern• Irregular gray-white matter junction• Underlying white matter signal changes

Pachygyria

•Thickened and flattened cortex• Blurred gray-white matter Junction• Underlying white matter signal changes

Schizencephaly

Cleft lined by Heterotopic gray matter extends from the ventricular (ependyma) to the periphery (pial surface) of the brain, traversing through the white matter.

Two types: Closed lip (type I) Open lip (type II)

Closed lip (type I) schizencephaly

Openlip (type2) schizencephaly

Porencephalic cyst resembles schizencephaly but CSF space is lined by gliotic white matter, in contrast to gray matter as in Schizencephaly

Porencephalic cyst

Anomalies Associated with Schizencephaly : Heterotopias, Septo-optic dysplasia,Absence of septum pellucidum Callosal dysgenesis

Hemimegalencephaly Hamartomatous overgrowth of a part or all of one

cerebral hemisphere

Associated with :• Epidermal nevus syndrome, • Klippel-Trenaunay–Weber syndrome, • Neurofibromatosis type 1

• Linear Nevus Sebaceous Syndrome(LNSS)

Conclusion• Variety of congenital anomalies of brain of

brain coexist • Clinical Presentation of various anomalies is

more or less same• Imaging plays an important role in diagnosing

Thank you

Imaging in developmental malformations of the brain

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