Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
CNS Malformations Ben Bly 2013 I am posting Eric Adelman’s slides which were much better than mine. Cavum Septum Pellucidum Normal finding Arachnoid Cysts • Pocket of fluid within arachnoid • Walls are arachnoid membrane • Occur close to cisterns, often near sylvian fissure – Do not communicate with CSF spaces – Present in 0.5% at autopsy Arachnoid Cysts • Clinical Findings – Asymptomatic – Global disturbances • Headache, signs/symptoms of increased ICP, enlarged HC, seizures, developmental delay – Focal neurologic symptoms related to location • Treatment – If symptomatic: surgical decompression, shunt Arachnoid cyst Porencephaly • Porencephalic cysts = cavity within brain parenchyma – Injury during development • Infarct / trauma – Or faulty induction and neuronal migration • Smooth walls, radially oriented gyri • May be in distribution of a cerebral artery • May or may not communicate with ventricle • May require shunting if enlarging or progressive RITE 2008: question 318 Porencephaly Hydranencephaly • Complete or near complete destruction of cerebral hemispheres with extreme dilation of ventricles • Catastrophic injury to brain < 28 weeks gestation • Multiple possible causes: in utero carotid occlusion, CMV or toxoplasma infection • Unlike anencephaly, cranium is intact Mega Cisterna Magna aka Retrocerebellar Arachnoid Pouch, Blake’s Cyst • Enlarged cisterna magna • Communicates with subarachnoid spaces • Posterior fossa = normal size • Unlike arachnoid cysts: – No mass effect on 4th ventricle Mega Cisterna Magna • ?Normal Variant • Often an incidental finding Dandy Walker Malformation Core features: • Absence (partial or complete) of the cerebellar vermis • Cyst like dialation of the 4th ventricle Commonly present: – Cerebellar hemispheres underdeveloped, displaced superiorly – Hydrocephalus RITE 2008 question 317 Dandy Walker Malformation Dandy-Walker Malformation Dandy Walker Malformation Clinical Findings • Usually evident in infancy • Apnea, hypo/hypertonia, motor delays, nystagmus, titubation, hydrocephalus • Sudden unexpected death, without herniation (vascular compromise from local ICP increases?) • Treatment • Cysto-/Ventriculo- peritoneal shunt • Many associated syndromes Walker-Warburg Syndrome • Dandy-Walker plus ocular Abnormalities – On 9q31, likely AR Other features: • Hydrocephalus • Lissencephaly Craniorachischisis Neural tube closure defects • Neural plate is converted into a closed neural tube during 3-4th weeks of development Neural tube closure defect • Craniorachischisis: – Most severe type of NTD in which brain and spinal cord are exposed to amniotic fluid and undergo degeneration – May have well developed forebrain and optic nerves Myelomeningocele Neural Tube Closure Defects • Myelomeningocele: – 95% associated with Chiari II malformations, hydrocephalus may occur – Malformations in spinal cord above the defect are common Anencephaly • Absence of both cerebral hemispheres • Failure of neural tube to close anteriorly • Infants are stillborn or die shortly after birth RITE 2010 question 319 Neural Tube Closure Defects • Anencephaly: – Absent or hypoplastic calvarium, “bat wing” deformity of sphenoid bone, only minimal cranial nerves II-V are present, pons/cerebellum/midbrain are grossly absent, aplasia of descending tracts – May be associated with visceral anomalies including a large thymus and hypoplastic lungs Anencephaly Encephaloceles • Herniation of intracranial contents through a skull defect • Fluctuant balloony mass covered by a membrane or normal skin, may pulsate • Occipital 75%, Frontal 25% • Seen with other malformations and in syndromes Encephalocele Neural tube closure defects • Encephalocele: – In anterior version, herniation occurs through frontoethmoidal junction and appears as hypertelorism or bulging tissue – May expand into nasal cavity (30%), pharynx, or orbit – Seen in 90% of patients with Meckel-Gruber syndrome • MG Syndrome –AR, lethal renal dysplasia, CNS malformations, polydactyly, pulmonary hypoplasia, hepatic developmental problems Defective prosencephalization Forebrain develops between 25-30 days gestation from a midline vesicle that is generated from the closed anterior neuropore. Holoprosencephaly Holoprosencephalic children Hypoteloric Proboscis RITE 2010: question 310 Holoprosencephalic cat Holoprosencephaly • Defective clevage • No division of prosencephalon (forebrain) – No interhemispheric fissure – Telencephalon = single lobe – No olfactory bulbs or tracts – Absence of midline structures Holoprosencephaly Craniofacial dysplasia • Cyclopia (single median eye) • Ethmocephaly: nose replaced by a proboscis located above hypoteloric eyes • Cebocephaly: hypotelorism and a nose with a single nostril • Premaxillary agenesis: hypotelorism, flat nose, midline cleft lip Holoprosencephaly • Failure of prosencephalon to cleave into symmetric cerebral hemispheres • Variable severity • Alobar • Semilobar • Lobar Semilobar Holoprosencephaly • Some differentiation of hemispheres, posteriorly • Diencephalon/Forebrain still fused in midline Semilobar Holoprosencephaly Lobar Holoprosencephaly • Hemispheres separated (interhemispheric fissure present) • Absent septum pellucidum • Fused thalami • Diffuse pachygyria • Interdigitation of frontal gyri Lobar Holoprosencephaly Agenesis of the Corpus Callosum Agenesis of the Corpus Callosum • Corpus Callosum forms front to back; myelinates back to front • If CC is partially absent, most likely posterior portion • Anterior part alone can be absent in holoprosencephaly, frontal schizencephaly, frontal porencephalic cysts • Thin CC: insult after completely formed (like PVL) Agenesis of the Corpus Callosum Agenesis of the Corpus Callosum RITE 2008: question 254; RITE 2009 question 269 Schizencephaly • Clefts in the cerebral hemispheres • Flawed development of cortical mantle during cell migration in first trimester • Genetic vs. acquired Schizencephaly • Most clefts near sylvian fissures • Clefts extend from surface of cortex into a ventricle • Neighboring gyral pattern abnormal • Lips are formed by dysplastic gray matter – (Porencephalic cyst lined by white matter) Schizencephaly • Open Lip: Lips of cleft are separated by CSF • Closed Lip: Lips of cleft are in contact Closed Lip Schizencephaly Closed Lip Schizencephaly Open Lip Schizencephaly Schizencephaly Clinical Findings • Often presents with seizures • Can be focal or generalized; infantile spasms • Hemiplegia Hemimegalencephaly • Brain volume increased from errors in neuroepithelial proliferation • Histology: increase in number of cells (neurons and glia) and cell size • Association of hemimegalencephaly with neuro-cutaneous disorders – Linear sebaceous nevus syndrome and hypomelanosis of Ito Hemimegalencephaly • Macrocephaly at birth • May have accelerated head growth in first few months of life • Present with seizures, developmental delay, hemiparesis, hemihypertrophy • Seizures sometimes require hemispherectomy or callosotomy Hemimegalencephaly Joubert Syndrome • Molar Tooth Sign • Complete agenesis of cerebellar vermis • 4th ventricle enlarged (batwing shape) • Other cerebral malformations, especially occipital encephaloceles Joubert Syndrome Chiari Malformation Chiari Malformations Chiari I Extension of cerebellar tonsils (sometimes posterior vermis) into upper cervical canal • Associated with syrinx Chiari II Displacement of cerebellar vermis (? medulla) in upper cervical canal • Associated with lumbar myelomeningocele Chiari III Occipital encephalocele Chiari IV Absence of cerebellum Chiari I with Syrinx Chiari III Lissencephaly • Disorder of neuronal migration • Abnormal migration of post-mitotic neurons from the ventricular zone to form the cortical plate • Smooth cerebral surface: absence of gyri, abnormally thick cortex, abnormal lamination Lissencephaly Defects of cellular migration Miller-Dieker syndrome – Lissencephaly – Microcephaly – Characteristic facies • Upturned nares, micrognathia, high forehead, thin upper lip, low set ears – Deletion on chromosome 17 X-linked defects of cellular migration (DCX mutation) Boys • Lissencephaly Girls • Subcortical band heterotopia – Gray matter in the wrong places RITE 2009: question 257 Polymicrogyria • Too many small abnormal gyri • Convolutions may not have sulci, or sulci might be bridged by fusion of overlying molecular layer which may give smooth appearance on surface • Gray-white interface not distinct Polymicrogyria Clinical findings depend on extent of abnormality • Diffuse: severe developmental delay and hypertonia • Focal deficits if focal • Seizures common Heterotopias • Collections of normal-appearing neurons in an abnormal location • Proposed mechanisms • Damage to radial glial fibers • Premature transformation of radial glia into astrocytes • Radial glial surface molecule deficiency • Isolated/multiple/diffuse • Usually no cause apparent Heterotopias • Periventricular Nodular Heterotopias – X-linked dominant (females only, lethal in males) – Filamin A, aka Filamin 1 – Failure of neuronal migration at an early stage from ventricular zone – Filamin A anchors membrane proteins to actin cytoskeleton Mobius syndrome Facial diplegia, bilateral abducens palsy, often involvement of other lower cranial nerves – Pathogenesis: selective ischemia of midline and paramedian zones of developing brainstem