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Congenital anomalies of brain radiology 2.pptx
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- 2. NORMAL BRAIN DEVELOPMENT VENTRALINDUCTION (Formation of vesicles and segmentation ) DORSAL INDUCTION (Formation of neural tube and dysjunction) CORTICOGENESIS (Histiogenesis &migration) MYELINATION Proliferation Migration Organization b. secondary neurulation a. Primary neurulation
- 3. DORSAL INDUCTION :Formation and closure of the neural tube . Occurs at 3-5 weeks NEURAL PLATE NEURAL FOLD NEURAL TUBE 3rd Wk - develops at cranial end of embryo as a thickening of ectoderm 4th week, the neural plate indents and thickens laterally. Neural fold bend upwards and meet in midline and fuse Dysjunction . NEURAL TUBE Primitive notochord – ventral Neural crest cells – collection of multipotent stem cells located at the side of the neural tube . Closure – begins in mid line– proceeds birectional in zipper like fashion. Ant neuropore – 25th wk, pst neuropore – 27th wk.
- 4. VENTRAL INDUCTION :Formation of brain segments and face. Occurs at 5-10 weeks of gestation Three vesicles: Prosencephalon – Telencephalon – Cerebrum - Diencephalon – Thalamus Mesencephalon – Mid brain Rombencephalon- Metencephalon – Pons and Cerebellum Myelencephalon – Medullaoblangata.
- 5. COTICOGENESIS: • Stem cellsarise around the primitive ventricular ependyma, forming the germinal matrix. • These neural stem cells (NSCs) are multipotent cells that generate the main CNS phenotypes neurons, astrocytes, and oligodendrocytes. • Development neuronal cells undergo proliferation, differentiation and histiogenesis. • Occurs at 8-21 weeks Neuronal migration from the germinal matrix to the surface resulting in cortical organization.
- 6. MYELINATION: Begins at6 months of gestation, matures by 3 years. Progress from - Caudal to cephalic - Dorsal to ventral - Central to peripheral
- 7. CONGENITAL BRAIN MALFORMATIONS Disordersof dorsal induction Disorders of ventral induction Disorders of corticogenesis Myelination Disorders Neural tube defects Chiari malformation Anencephaly Cranial dysraphism ( CEPHALOCELE) Holo- prosencephaly Dandywalker spectrum Corpus callosal agenesis Lissencephaly Heterotopias Polymicrogyria Schizencephaly FCD(I, III) Leukodystrophies Dysmyelination Microcephaly , Hemimegalencephaly Focal cortical dysplasia Proliferation Migration Organisation
- 8. Results inthe defects of closure Anencephaly Encephaloceles Chiari malformations Spinal dysraphism DISORDERS OF DORSAL INDUCTION
- 9. ANENCEPHALY: • Occurs whencephalic end of the neural tube fails to close - absence of cranial vault, cerebral hemispheres, diencephalic structures. Acrania- no skull + normal brain tissue Exencephaly : no skull + amorphous brain Anencephaly : No skull + No brain. Acrania -anencephaly sequence
- 10. ANTENATAL USG :detectableat 11ks ,100% accuracy at 14k • No brain tissue above the orbits. • Absent calvarium ( may found parts of occipital bone). • Exencephaly – small amount of neural tissue. • Low CRL • Frog eye or micky mouse appearance - coronal plane due to absent cranial bone and/or brain and bulging orbits. • Poly hydramnios- due to impaired swallowing
- 11. CEPHALOCELE • Refers tothe herniation of intracranial contents through the defect in the dura and calvarium. • Etiology multifactorial with the involvement of the genetic and environmental factors. • Encephaloceles are considered to be a spectrum of neural tube defects caused due to failure of neurulation, i.e., failure of the neural tube closure. • Can be a post neurulation event – most accepted
- 12. CEPHALOCELES Meningocele Meningo encephalocele Meningoencephalo cystocele Atretic cephalocele Gliocele CSF CSF Brain ( dysgenetic, nonfunctioning) CSF Brain Ventricles Dura,fibrous tissue, Degenerated brain tissue Glial lined pouch- CSF
- 13. CEPHALOCELES Based on locationof defect Occipital-m/c parietal Fronto Ethmoidal @ Sincipital Skull base Atretic cephalocele – midline scalp masses. Assosciated with folate deficiency , valproic use Assosciated with persistent falcine sinus. Frontonasal-m/c- patent fonticulus frontalis Nasoethmoidal –patent foramen caecum Nasoorbital - through maxilla and lacramial bone into inferomedial orbit Sphenopharyngeal - sphenoid body Sphenoethmoidal Transsphenoidal – cribriform plate
- 14. Nasoethmoidal and nasoorbitalencephalocele. Herniation of the brain content into the prenasal space through foramen cecum anterior to crista galli.
- 15. Parietal encephalocele/gliocoele T1 T2T1+C Herniation of the brain content through the defect in the left parietal bone . large porencephalic cyst at the site of herniation. sagittal sinus ( has herniated into the sac
- 16. ARNOLD CHIARI MALFORMATIONS •Chiari malformations are a group of defects associated with congenital caudal displacement of the cerebellum and brainstem.
- 17. TYPE FINDINGS 0 Syrinxwithout cerebellar tonsillar, or brain stem descent 1 m/c. peg-like cerebellar tonsils displaced into the upper cervical canal through the foramen magnum 1.5 Variant of Chiari I malformation- caudal descent of cerebellar tonsils and brain stem 2 Displacement of the medulla,4th V, and cerebellar vermis through the foramen magnum + lumbosacral spinal myelomeningocele. 3 Chiari II +occipital and/or high cervical encephalocele 4 Severe cerebellar hypoplasia without displacement of the cerebellum through the foramen magnum ---- probably a variation of cerebellar hypoplasia 5 Absent cerebellum Herniation of the occipital lobe through the foramen magnum
- 18. Small posterior fossa Peg liketonsillar herniation + effaced premedullary CSF space Syringomyelia 30-70% +hydrocephalus in 10% of CM1 Chiari malformation 1.5 CM1+ brain stem caudal decent Chiari malformation type 0 Normal posterior foss anatomy + syringomyelia. Etiology: Underdeveloped occipital enchrondrium, small posterior fossa, downward herniated hind brain obstructed FM, lack of communication between cranial/spinal CSF compartments. CHIARI MALFORMATION TYPE I
- 19. Tonsillar and vermian herniation+medullary kinking Myelomeningocele Towering cerebellum+ Tectum beaking + hydrocephalus Callosal dysgenesis + masa intermedia CHIARI MALFORAMTION TYPE II Etiology: presence of open spinal dysraphism + CSF leakage+ lack of distension of embryonic vesicles during development + markedly small post fossa and complex malformations
- 20. Etiology- Abnormally increasedproliferation of progenitor cells together with failure of normal neurogenesis, apoptosis. CHIARI III MALFORMATION T2 Cephalocele - herniated dysplastic brain and CSF in continuity with a lateral ventricle T1A T2 Extension of the lateral ventricles into the cephalocele.
- 21. DISORDERS OF VENTRALINDUCTION
- 22. Fetal brain failsto bifurcate into two hemispheres. HOLO -Single ventricle involving the prosencephalon (Pros) of brain (encephaly). Holoprosencephaly – Degree of severity NORMAL LOBAR SEMILOBAR ALOBAR HOLOPROSENCEPHALY
- 23. • As ventralinduction is closely related to facial development, it is also associated with number of characteristic facial anomalies. • The distinction between 3 forms is primarily based on the presence or absence of a midline fissure separating the hemispheres. Aborted fetus with alobar holoprosencephaly with central proboscis , cyclops , and slit-like oral cavity .
- 24. HOLOPROSENCEPHALY ALOBAR SEMILOBAR LOBAR Absentseptum pellucidum Crescent shaped monoventricle Absent septum pellucidum Absent septum pellucidum Absent – IHF, 3rdV, falx Brain- gyric/ shallow sulcations Partially formed T, O horns. Fused BG, thalami Partially formed IHF,3rdV, falx Partially separated BG CC – body and genu absent Falx, IHF +--except antinferiorly Lt & 3rd v +, frontl hrn- dysplastic Thalami and BG are separated. CC – + / hypoplastic/ absent
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- 26. Telencephalon has 3major commisures Anterior commisure Corpus callosum Posterior commisure 8th fetal wk 11th fetal Wk 13-14 weeks – genu, rostrum and body 18-19 w - splenium,
- 27. Corpus callosal agenesis CompleteCorpus callosal agenesis Partial Corpus callosal agenesis Genu and body present and thickened Rostrum and splenium are absent Partial posterior agenesis:– Hc, splenium, +/- posterior body • Agenesis can be isolated or can be a part of congenital malformations – Chiari II, migration disorders, dandy walker malformation, holoprosencephaly.
- 28. Viking helmet ormouse head apperance. Mid and posterior body parts not seen. Dilated occipital horns (colpocephaly) and widely placed lateral Ventricle – racing car sign
- 29. POSTERIOR FOSSA CYTSICMALFORMATIONS DANDY WALKER SPECTRUM Dandy -walker malformation Inf Vermian hypoplasia Blake’s pouch cyst Mega cisterna magna
- 30. • The tegmentovermianangle is an important measurable parameter in the assessment of posterior fossa abnormalities in the fetus. line 1: along the dorsal surface of the brainstem parallel to the tegmentum line 2: along the ventral surface of the vermis • Tegmento- vermian angle <- 18 degree. • Fastigium –declive line – extends from fastigium of 4th V to the declive- Approx 50% of vermis should lie below this line.
- 31. DW malformation Inferiorvermian hypoplasia Blakepouch cyst Posterior fossa - large. Vermis hypoplasia + upward &superior rotation, elev torcula & tentorium Posterior fossa -Normal Cystic dilatation of 4V T-V angle >45 degrees Hydrocephalus – yes Megacisterna magna Vermis hypoplasia Fastigium – upward rotation 4V- enlarged T-V angle -18-45 deg Hydrocephalus - yes Vermis – normal (+mass effect) 4V- enlarged T-V angle – normal Hydrocephalus - yes Posterior fossa – N/ Large Posterior fossa -Normal Vermis – normal 4V- normal Hydrocephalus -no T-V angle – normal
- 32. Blake's pouch cyst,sometimes called persistent Blake's pouch, is a cystic structure of the posterior fossa representing an outpouching of the fourth ventricle into the area of the cisterna magna.
- 33. Retrocerebellar arachnoid cyst. Imagingfeatures: • Vermis – normal (+mass effect) • 4th ventricle- normal • T-V angle – normal • Posterior fossa – normal • Hydrocephalus – no • Normal fastigium • +/- scalloping of occipital bone
- 34. CONGENITAL BRAIN MALFORMATIONS Disordersof dorsal induction Disorders of ventral induction Disorders of corticogenesis Myelination Disorders Neural tube defects Chiari malformation Anencephaly Cranial dysraphism ( CEPHALOCELE) Holo- prosencephaly Dandywalker spectrum Corpus callosal agenesis Lissencephaly Heterotopias Polymicrogyria Schizencephaly FCD(I, III) Leukodystrophies Dysmyelination Microcephaly , Hemimegalencephaly Focal cortical dysplasia Proliferation Migration Organisation
- 35. PROLIFERATION MIGRATION CORTICALORGANIZATION • 2nd & 4th M of GA. •Both neuronal & glial cells develop from the neuroblast precursors in the ventricular and subventricular zones. Too many too few Abnormal neurons • 3rd to 5th M GA. •Neurons migrate along the fascicles formed by radial glial cell processes, from germinal zones peripherally to the cortex. •Inside – out pattern ( early migrating cells are located deep in the cortex). Under migration Overmigration Ectopic migration •Starts at 22 Wk continues until 2 years •Vertical and horizontal organization of neurons within cortex. •Neurons differentiate into several cell types, establish connectivity with other neurons. •Lobulation , operculization, sulcation and gyration and myelination Gyral formation and cortical organization CORTICAL DEVELOPMENT
- 36. CEREBRAL CORTEX: Normal neocortex: -6 layered neocortex present in over 90% brain - olfactory paleocortex & hippocampal archicortex composed of 3 layers - Normal cortex is approx 3mm in thickness Thinner at depth of sulcus (*) Thicker at crown of gyrus ( ) T1W image – Normal Gyri
- 37. Decreased proliferation Increasedproliferation Abnormal proliferation Microcephaly Macrocephaly Cortical tubers FCD ( IIB) Hemimegalencephaly PRIMARY- defect in brain development SECONDARY- resulting from an insult that affects fetal, neonatal, or infantile brain growth. Ischemia, infection, maternal diabetes, and trauma are the m/c causes NEUROPROLIFERATIVE ERRORS
- 38. MICROCEPHALIES: • Decreased cellproliferation or increased apoptosis. • Microcephaly ( small head) – head circumference >3SD below the mean for age and sex. • Craniofacial ratio is decreased (usually <- 1.5:1). Three types : Microcephaly with simplified gyral pattern(mild) Microlissencephaly (severe) Microcephaly with extensive poly microgyria.
- 39. craniofacial disproportion ,slopingforehead, thin dysplastic corpus callosum . simplified gyral pattern with too few gyri and shallow-appearing sulci. T1W T2 Simplified gyri and abnormally shallow sulci are the hallmarks of MSG. The cortex is normal or thinned, not thickened. The gyri are also reduced in number and demonstrate a "simplified" pattern Microcephaly with simplified gyral pattern
- 40. No sulcation inthe cerebrum, a hypoplastic cerebellum, and a small brain stem with Dandy-Walker syndrome. shows agyria of cortex. Smooth surface, shallow sylvian fissure. T1W T1 Severe microcephaly and abnormal sulcation. The brain is extremely small, and the sulcation pattern appears greatly simplified or almost completely smooth. The cortex is thickened, usually measuring more than 3 mm, MICROLLISSENCEPHALY
- 41. Focal cortical dysplasia FCD– I with abnormal cortical lamination FCD –II with dysmorphic neurons and balloon cells FCD-III: type – I with additional lesion in same lobe A. alterations in radial cortical migration B. alterations in tangential cortical migration C. alterations in radial & tangential cortical migration A.Only with dysmorphic neurons B.Dysmorphic neurons & balloon cells A.Hippocampal sclerosis B. Tumors C. Vascular malformations D. Lesions acquired in early childhood • Localized regions of non neoplastic malformed gray matter. • common cause of medically refractory epilepsy in both children and adults. Surgical resection is an increasingly important treatment option.
- 42. IMAGING FEATURES: • Loclalizedarea of increased cortical thickness. • Blurring of white matter-grey matter junction with abnormal architecture of subcortical layer • T2/FLAIR signal hyperintensity of white matter with or without the transmantle sign • T2/FLAIR signal hyperintensity of grey matter • Abnormal sulcal or gyral pattern • Segmental and/or lobar hypoplasia/atrophy TRANSMANTEL MR SIGN : High T2/FLAIR signal extending from the ventricle to the cortex
- 43. IMAGING FEATURES: • Large,dysplastic-appearing hemisphere • Thick cortex + focal subcortical masses of dysplastic GM • Falx inserts off midline. • Ipsilateral ventricle large. • Focal mass of heterotopic GM can mimic neoplasm. • WM abnormally myelinated(T2 hyperintensity). • Blurred grey -white matter junctions • Enlarged and dysplastic hamartomatous overgrowth of part or all of the cerebral hemisphere • Associated with syndromes such as epidermal nevus syndrome, proteus syndrome, unilateral hypomelanosis of Ito, NF -I, Klippel-Trenaunay syndrome,TS. HEMIMEGALENCEPHALY
- 44. DISORGDERS OF MIGRATION Ectopicmigration Over migration Under migration Classic lissencephaly (type I) Cobble stone lissencephaly (type I) Heterotopia Subependymal Subcortical Band heterotopia
- 45. • Migrational disturbance •Cluster of normal neurons (grey matter in abnormal locatiosn due to impaired migration. Heterotopic grey matter is isointense with the cerebral cortex in all MR sequences. Categorization: Based primarily on location and morphology. The pattern of distribution may help to define the underlying genetic cause. 1) PERIVENTRICULAR NODULAR HETEROTOPIAS: GM nodules lining the ventricular walls, varying in number, location, size and shape. May be assc with other brain or systemic malformations. m/c is ventriculomegaly f/b agenesis of the corpus callosum and cortical dysplasia DD: Tuberous sclerosis- subependymal nodules( not isointense to GM, may calcify and /or enhance) HETEROTOPIAS
- 46. Subcortical Heterotopias : •Large, focal, mass-like collections of neurons are found in the deep cerebral white matter anywhere from the ependyma to the cortex. • Diffuse reduction in size of the hemisphere, underlying distorted ventricles. • Diminished and abnormal white matter. • Thinned overlying cortex with shallow sulci. • Distorted basal ganglia. • Follow GM on all sequences, do not demonstrate edema, and do not enhance. T1 , T2 show mass of heterotopic GM , thin overlying cortex , deformed underlying ventricle mimicking neoplasm.
- 47. Due to DCX-1mutation - results in a thick assymteric band ( laminar band ) of GM heterotopia. Located any where in WM from germinal zone to subcortical region. Clinical : Almost always in female patients Imaging: • looks like "double cortex“ • Thin, gyriform cortex • Normal-appearing WM under cortex • Smooth inner band of GM • Normal-appearing periventricular WM BAND HETEROTOPIA:
- 48. • Means "smoothbrain." • Malformations due to widespread abnormal transmantle migration include agyria, pachygyria, and band heterotopia. All are part of the lissencephaly spectrum. Types: • Classic type I lissencephaly • Type 2 lissencephaly-Cobblestone Lissencephaly • Lissencephaly with cerebellar hypoplasia. • Variant LIS (vLIS) • Subcortical band heterotopia LISSENCEPHALY
- 49. Type I (classic): Arrested neuronal migration Mutations- Multiple gene -LIS1, DCX1. MRI shows: Complete or partial lack of gyration • Agyria( Thick cortex with absent gyri) • Pachygyria( Broad flat gyri with shallow sulci) • Thick cortex (12-20mm) • Cell arrest In radial columns Shallow, underdeveloped sylvian fissure- figure of 8 appearance to the brain.
- 50. Cobblestone lissencephaly: Large defectsof the glial limiting membrane lead to abnormal migrating neurons to the subarchnoid space. Difficult to distinguish from polymicrogyria. Uneven, nodular, pebbly brain. Occurs as a part of congenital muscular dystrophy syndromes( CMD). • Lack of normal sulcation • Multinodular surface to the cortex (cobblestone), most pronounced anteriorly. • Abnormal signal intensity of the subcortical white matter that can be related to edema or hypomyelination.
- 51. T2 Cobblestone lissencephaly associatedwith muscle eye-brain disease. Enlarged, fused collicular plate , Small pons with "kinked“ appearance to the midbrain, and the thin upwardly arched CC. Frontal predominant cobblestone lissencephaly Cobblestone appearance of thickened frontal gyri. Delayed myelination , cobblestone cortex , & cerebellar cysts
- 52. ORGANIZATION/ POSTMIGRATIONAL DISORDERS Polymicrogyria SchizencephalyFCD ( type I and III) Post migrational microcephaly
- 53. POLYMICROGYRIA Neurons reach thecortex but organize abnormally Can be genetic or from intrauterine insult ( infection/ ischemia) IMAGING: • Irregular cortex with numerous small convolutions and shallow or obliterated sulci. • The appearance is that of tiny miniature gyri piled on top of other disorganized gyri • M/C- bilateral perisylvian areas(60-70%). • Cortex may appear normal or often thickened
- 54. SCHIZENCEPHALY • A cerebralcleft lined by polymicrogyric or heterotopic gray matter extending from ventricular ependymal surafce to the pial surface. - Type I: Closed lip - Walls of cleft apposed, no interposing CSF - Type II: Open lip -Walls of cleft separated by CSF. • COL4A1 mutation ,Destructive vascular lesions (MCA occlusion) and infections (e.g., TORCH) occurring before 28 fetal weeks are considered likely etiologies • Associated with range of other macroscopic abnormalities involving the septi pellucidi, corpus callosum, optic chiasm, and hippocampus.
- 55. Open lip schizencephaly Closedlip schizencephaly Look for a dimple in the ventricular wall if suspecting – closed lip
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