Patterns of Congenital Malformation

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Introduction:

·         When dealing with malformations, it is very important to have the mentality that almost no two malformed CNS are the same. However, they may be separated into several major categories and pattern as listed here. Categories of developmental disturbances  

·         It is often useful to break down the pattern of pathologic changes into small components when analysing a malformed case. Pattern of congenital malformations and structural abnormalities in the CNS

·         Every malformed CNS should therefore be treated as an individual case. It is very important to document clearly the malformation with word and photographs.

·         In many cases, it is very important to distinguish the primary events from the secondary events; with the same token, it is also important to distinguish malformation from disruption.

Categories of developmental disturbances  Head

• Agenesis or aplasia (e.g., agenesis of the corpus callosum)

• Hypoplasia

• Hyperplasia or hypertrophy (e.g., hemimegaencephaly)

• Failure to fuse (e.g., anencephaly)

• Failure to divide (e.g., holoprocenphaly) or canalize (e.g., imperforate anus)

• Failure to undergo apoptosis (e.g., migration disorders)

• Failure to arrange into normal architecture (e.g., lissencephaly)

• Persistence of temporary structures (e.g., thyroglossal duct)

• Multiplication of parts, producing supernumerary structures (e.g., digits) or accessory organs (e.g., spleen)

• Heterotopia or ectopia (e.g., glioneuronal heterotopia)

• Hamartoma

• Congenital neoplasm

Pattern of congenital malformations and structural abnormalities in the CNS

Cerebral hemisphere  Head

• Germinal matrix

• Premature exhaustion of germinal matrix

• Periventricular heterotopia

• Neural tube defect

• Craniorachischisis

• Anencephaly and exencephaly

• Iniencephaly

• Cranioectomesodermal hypoplasia

• Rudimentary meningocele/meningomyelocele

• Abnormalities with features suggestive of a neurotube defect

• Encephalocele (occipital, parietal, basal, frontoethmoidal)

• Nasal cerebral heterotopias (nasal glioma, sequestered encephalocele)

• Rudimentary meningocele/meningomyelocele

• Disruption (such as amnion rupture sequence)

• Defects of the mediobasal prosencephalon

• Aprosencephaly

• Atelencephaly

• Holoprosencephalon (alobar, semilobar, lobar)

• Arhinencephaly (isolated absence of the olfactory bulb and tract)

• Abnormal gyral pattern without proved histologic abnormalities

• Histologically abnormal cortex and subcortical white matter with or without macroscopic abnormalities

• With abnormal macroscopic gyral pattern (e.g., polymicrogyria or pachygyria)

• With normal macroscopic gyral pattern (e.g., cortical dysplasia)

• Disorganized cortex combined with abnormal cortical vascular structure

• Heterotopia in white matter

• Leptomeningeal heterotopia

• Cerebral mantle defects

• Porencephaly

• Schizencephaly

• Hydrancephaly

• Agenesis of corpus callosum

• Hydrocephalus

• Hydrocephalus ex vacuo

• Hydrocephalus associated with identifiable malformation or structural defects

• Obstruction/agenesis of the aqueduct and/or 4th ventricle

• Chiari malformations

• Dandy-Walker syndrome

Cerebellum  Head

• Aplasia or hypoplasia

• Vermian agenesis and hypoplasia

• Rhombencephalosynapsis

• Rhombencephaloschisis

• Dandy-Walker syndrome

• Tectocerebellar dysraphia

• Joubert syndrome

• Walker-Warburg syndrome

• Other syndromes (e.g., oro-facial-digital syndrome II and IV, COACH)

• Abnormal architecture

• "Cerebellar polymicrogyria"

• Heterotaxia

• Heterotopia

• Dysplasia

• Atresia of the 4th ventricle

• Abnormalities of cerebellar nuclei

• Herniation of cerebellar content

• Chiari malformations

Brain stem  Head

• Abnormal positions of nuclei and structures (eg. Miller-Dieker syndrome, Chiari II malformation)

Spinal cord  Head

• Neural tube defects

• Spina bifida

• Meningocele

• Rudimentary meningocele/meningomyelocele

• Myeloschisis

• Meningomyelocele

• Myelocystocele

• Chiari II malformation

• Split cord malformations

• Hydromyelia

• Syringomyelia

• Sacrococcygeal regions

• Caudal regression syndrome

• Persistence neuroenteric canal and neuroenteric cyst

• Tethered cord syndrome

• Fatty masses associated with neurospinal dysraphism (Lipomyelomeningocele, leptomyelolipoma)

• Blood vessels

• Abnormal cortical blood vessels with or without disorganized cortex

• Persistence of the primitive vascular rete

• Aneurysmal dilatation of the great vein of Galen

• Arteriovenous malformation

NeuroLearn NeuroHelp Malformations  For Comment: KarMing-Fung@ouhsc.edu