Ultrasound Evaluation of the Ultrasound Evaluation of the Central Nervous System Central Nervous System ••CNSCNS malformations are the second most Mani Montazemi, RDMS frequent category of congenital anomaly, Director of Ultrasound Education & Quality Assurancee after congenital heart disease Baylor College of Medicine Division of Maternal-Fetal Medicine ••PoorPoor timing of the examination, rather than Department of Obstetrics and Gynecology Texas Children’s Hospital, Pavilion for Women poor sensitivity, can be an important factor Houston Texas & in failing to detect a CNS abnormality Clinical Instructor Thomas Jefferson University Hospital Radiology Department Fetal Head Philadelphia, Pennsylvania Fetal Head Central Nervous System Brain Development 9 -13 weeks Rhombencephalon 5th Menstrual Week •Gives rise to hindbrain •4th ventricle Arises from the posterior surface of the embryonic ectoderm Mesencephalon •Gives rise to midbrain A small groove is found along •Aqueduct the midline of the embryo and the edges of this groove fold over to form a neuro tube that Prosencephalon gives rise to the fetal spinal •Gives rise to forebrain rd cord and brain •Lateral & 3 ventricles Fetal Head Fetal Head Ventricular view Neural Tube Defects ••LateralLateral ventricles ••ChoroidChoroid plexus Group of malformations: Thalamic view • Anencephaly ••MidlineMidline falx •Anencephaly ••CavumCavum septiseptipellucidi pellucidi ••CephalocelesCephaloceles ••ThalamiThalami ••SpinaSpina bifida Cerebellar view ••CerebellumCerebellum ••CisternaCisterna magna Fetal Head Fetal Head 1 Anencephaly Anencephaly ••LethalLethal abnormality • Defect is covered by a membrane known as ••AbsenceAbsence of the brain & •Defect is covered by a membrane known as lack of the cranial vault cerebrovasculosa ––NoNo soft tissue above ••OftenOften contiguous with cervical spine defect orbits ••TheThe prevalence of anencephaly in the United States in 2001 was 9.40 per 100,000 live births National Center for Health Statistics Fetal Head Fetal Head Anencephaly Anencephaly ••FetalFetal face from the orbits to the ••BulgingBulging eyes chin is usually normal ••LargeLarge tongue ••FrontalFrontal bone is defective above the ••VeryVery short neck orbits ••ParietalParietal bones & occipital bone are absent Fetal Head Fetal Head Anencephaly Anencephaly ••ElevatedElevated MSAFP ––LeakageLeakage thru open neural tube ••PolyhydramniosPolyhydramnios after 25 wks ––FailureFailure to swallow ––ExcessiveExcessive micturition ––FailureFailure of reabsorption of CSF Preterm labor and delivery Routine 2nd ultrasound 96% MSAFP 78% Fetal Head Kooper et al, Prenat Diagn. 2007 Jan;27(1):29-33 Fetal Head 2 Early Recognition of Anencephaly Anencephaly ••MoreMore common ––inin girls than boys ––inin whites than blacks ––inin Irish compared to other ethnic groups ––inin mothers at the younger and older extremes of age ••AssociatedAssociated malformations ––SpinaSpina bifida “crown-chin to crown-rump length ratio” ––CleftCleft lip or palate SepulvedaW, Sebire NJ, FungTY, Pipi E, Nicolaidas KH – Clubfoot Am J Obstet Gynecol. 1997, 176(4):852 –Clubfoot Fetal Head Fetal Head Cephalocele Cephalocele ••ProtrusionProtrusion of intracranial contents through a ••HerniatedHerniated bony defect of the skull ––BrainBrain tissue & CSF ––85% 85% • Size - variable •Size -variable ••EncephaloceleEncephalocele ––MeningesMeninges & CSF ––15% 15% ••CranialCranial meningocele Fetal Head Fetal Head Cephalocele Cephalocele ••75%75% Occipital ••OtherOther CNS anomalies common ––WesternWestern hemisphere ––AbsentAbsent cavum septiseptipellucidi pellucidi ••13%13% Frontal ––AnomalousAnomalous corpus callosum ––AsianAsian population ––DorsalDorsal interhemisphericinterhemisphericcysts cysts ••12%12% Parietal ––ChiarimalformationsChiari malformations ––DandyDandy Walker malformation ––CerebellarcorticalCerebellar cortical dysplasia Fetal Head Fetal Head 3 Occipital meningocele with an Cephalocele associated Dandy-Walker cyst Fetal Head Fetal Head Cephalocele Cephalocele Usually occurs as an isolated lesion, but may be a part of a syndrome ••Meckel-GruberMeckel-Gruber syndrome ––Cepahalocele+Cepahalocele + B/L polycystic Kid + post-axial polydpolydactylyactyly ••Walker-WarburgWalker-Warburg syndrome ––Lissencephaly+Lissencephaly + cerebellarcerebellarhypoplasia+ hypoplasia + Dandy-Walker ccystyst + occular abnormalities ••AmnioticAmniotic band Syndrome ––CanCan involve any part of skull Fetal Head Fetal Head Structural Midline Defects NTD – Cranial Signs ••HighHigh incidence of associated anomalies ••LemonLemon sign: head deformity ––StructuralStructural & chromosomal ••BananaBanana sign: cerebellar deformity ••KaryotypingshouldKaryotyping should be offered ••VentriculomegalyVentriculomegaly Fetal Head Fetal Head 4 Spina Bifida or Spinal Dysraphism ••AA defect that can occur Splayed dorsal ossification centers anywhere along the spinal axis ••LowerLower spine more common than higher ••SpinalSpinal cord and nerve roots exposed Fetal Head Fetal Head Remember Spina Bifida There are several forms of spina bifida ••OssificationOssification occurs from cervical to There are several forms of spina bifida coccygeal •Ventral•Ventraldefectsdefects (rare) ––SplittingSplitting of the vertebral body ––LowerLower levels ossify later ––OccurrenceOccurrence of a cyst that is neuroentericneuroentericin in ––LumbosacralLumbosacral area appears open & wider origin Higher level Lower level •Dorsal•Dorsaldefectsdefects (most common) ––Occulta(closedOcculta (closed spina bifida) ––Aperta(openAperta (open spina bifida) Fetal Head Fetal Head Closed Spina Bifida Skin-Covered NTD ••SpinaSpina bifida occultaocculta(15%) (15%) ––SmallSmall defect completely covered by skin ––Asymptomatic/incidentalAsymptomatic/incidental findings SpinalThere cordis excess extending soft tissuedown belowdistributed L5, compatible broadly ove witr hthe tethering defect Fetal Head Fetal Head 5 Skin-Covered NTD NTD ••LesionLesion level is most predictive of ambulatory function ––HigherHigher lesion levels associated with disphagia ––TheThe absence of covering membrane associated with scoliosis Fetal Head Fetal Head Open Spina Bifida Classifications of Spina Bifida ••SpinaSpina bifida apertaaperta(85%) (85%) AB ––NeuralNeural canal may be exposed ––DefectDefect may be covered by a thin meningealmeningealmembrane membrane A) Meningocele – If the tumor contains purely meningesmeninges && CSFCSF B) Myelomeningocele – protrusion of a sac containing CSF & neural elementelementss Fetal Head Fetal Head Meningocele Vs. Myeloschisis Myelomeningocele It contains solid component due to presence of neural elements within the herniated sac Fetal Head Fetal Head 6 Reversal of Chiari Malformation “Healed” back at birth Fetal Head Fetal Head Cerebellar View - Cisterna Magna ••Size:Size: 2-10 mm ––<< 2 mm spina bifida (ACII) ––>> 10 mm Dandy-Walker T P FH P CSP T FH Fetal Head Fetal Head Arnold-Chiari II Spina Bifida - Arnold-Chiari ••ShallowShallow posterior fossa ••HerniationofHerniation of the cerebellar vermis through ••SmallSmall cerebellar diameter foramen magnum ••“Banana”sign“Banana” sign if severe ••MalformationMalformation is present in almost every case of ••FourthFourth ventricle is displaced downward thoracolumbar, lumbar, and lumbosacral myelomeningocele myelomeningocele inside the neural canal Fetal Head Fetal Head Search for ONTD 7 31 yo woman for “size and dates” evaluation MSAFP was normal No risk factors for fetal anomalies Fetal Head Fetal Head Coronal sonogram of the sacral spine Mid sagittal sonogram of the sacral spine Fetal Head Fetal Head Axial sonogram of the brain Mid sagittal sonogram of the distal spine at the level of ventricular atrium Fetal Head Fetal Head 8 Axial sonogram of the brain WhatSkin is your Covered best guess Spina at the diagnosis? Bifida at the level of posterior fossa Fetal Head Fetal Head Once you have observed the spina bifida cystica, Open neural tube defect WhatWith a closedis thelesion significance one would anticipate of the what is the key sonographic observation that leads to that the mother would demonstrate a normal MSAFP is associatedthe conclusion with that Arnold-Chiari this is a “closed” II malformation lesion? MSAFP test is“normal” only useful for MSAFP?detection of the open NTD The presence of a normal MSAFP does not exclude the possibility of the open NTD because only 80-85% of open Myelomeningoceles are detected by MSAFP testing Fetal Head Fetal Head WhichThe is more AFAFP sensitive is positive for confirming in virtually that the The closedWhich lesions lesion typically has have the a better better prognos is In part this is due to the lack of the Chiari II malformation lesion is “skin ALLcovered”:open NTDsMSAFP or AFAFP? andprognosis: a lack of development open ofor hydrocephalus closed? Fetal Head Fetal Head 9 Dandy-Walker Complex Dandy-Walker Malformation ••DefectDefect in the cerebellar vermis through which the •Dandy-Walker malformation cyst communicates with the 4thth ventricle – Complete or partial agenesis of the cerebellar vermis –Complete or partial agenesis of the cerebellar vermis ••CerebellarCerebellar hemispheres are separated ––EnlargedEnlarged posterior fossa •Dandy-Walker variant ––PartialPartial agenesis of the cerebellar vermis ––WithoutWithout enlargement of the posterior fossa •Mega cisterna magna ––NormalNormal vermis & 4thth ventricle Fetal Head Fetal Head Cisterna Magna – Caution Cisterna Magna – Caution InferiorInferior vermisvermis << 1818 wkswks Reevaluation at 20 to 22 postmenstrual weeks is