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Ana Monteagudo, MD

Take Your Brain Ultrasound to the Next Level 2: The Median Plane

Outline

•Definition

•Obtaining the median plane• TAS; TAS 3D• TVS; TVS 3D

• Sonographic anatomy of the median plane

• Examples of anomalies seen on the median plane of the fetal brain

Why Is It Important to Obtain the Median Plane of the Fetal Brain?

• It allows easy, reliable & quick imaging of the• Corpus callosum• Tectal (quadrigeminal ) plate• Posterior fossa

• Vermis

•Arteries , veins, and sinuses

• It aids in the diagnosis of abnormalities involving these structures

Why Is It Important to Obtain the Median Plane of the Fetal Brain?

Condition Prevalence/births

Congenital heart defects 1/100*

Down syndrome 1/700 *

Agenesis of the corpus callosum 7/1,000 **

Congenital hydrocephaly 0.2 to 0.8/1000 ***

Anencephaly 1: 5,000 - 10,000 **

Dandy Walker Malformation 1: 25,000 -35,000 **

* Data from CDC: Centers for Disease Control and Prevention**Data from NORD: National Organization of Rare Disorders*** Data from ISPN: International Society for Pediatric neurosurgery

Is defined as a vertical plane through the midline of the head/brain that divides it into right and left halves.

Median Plane*

* Most use “Mid-sagittal”, a term the official Nomina Anatomica(Basel ) does not endorse

Median Plane TransabdominallyTransfrontal view*

Median Plane TransabdominallyTransfrontal view*

• Imaging through the anterior fontanelle or metopic suture results in excellent quality images, however at times it may be hard to access

• It also requires a good acoustic window (bladder comfortably full ~300 cc)

*Visentin et al., 2001

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Box ABox A Box BBox B

Box CBox C

+ Rotation - Rotation

Median Plane TransabdominallyUsing 3D: Transfrontal view

The X, Y and Z controls (knobs)

perform rotations around their

respective axis

Using 3D TAS Acquired Volume

Generate the median section very slightly off the midline

Coronal Median

Median Plane Transvaginally

• The anterior fontanelleprovides an acoustic window resulting in high resolution and detailed images

Anatomic StructuresAnatomic StructuresCorpus CallosumCorpus Callosum

Thalamus (3V)Thalamus (3V)

Tela chroideaTela chroidea

Cavum Septi PellucidiCavum Septi Pellucidi

Tectum (corpora quadrigemina)Tectum (corpora quadrigemina)

Posterior fossaVermisCisterna magna4th ventricleFastigium

Posterior fossaVermisCisterna magna4th ventricleFastigium

Corpus Callosum & Cavum Septi Pellucidi

Embryology

The role of Gestational Age

Anatomy

EmbryologyCorpus Callosum & Cavum Septi Pellucidi

•Anatomically, by 13-18 weeks, the anterior part of the corpus callosum and the pericallosalarteries are formed

•However, by ultrasound the corpus callosum and cavum septi pellucidi may not be consistently imaged until after 18 weeks.

14 wks

30 wks

15 wks

19 wks

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16 weeks

22 weeks 34 weeks

11 weeks

The role of Gestational AgeCorpus callosum & cavum septi pellucidi

The role of Gestational AgeCorpus callosum & cavum septi pellucidi

17 weeks

25 weeks

25 2/7 weeks

• Normal pericallosal arteries should predict normal development of the corpus callosum

The role of Gestational AgePericallosal Arteries

• Several authors have demonstrated the presence of the pericallosal arteries in the 1st trimester using 2D and 3D Power Doppler

• Few are aware and use this fact. It may be used to screen pregnancies at increased risk of AGCC

Pati M et al. J Ultrasound Med 2012;31:231–237. 7Diaz-Guerrero L et al. Fetal Diagn Ther 2013; 34:85–89.

Conturso R et al. Fetal Diagn Ther 2015;37:305–309

Pericallosal Arteries at 11-13 weeks

• Before 18 weeks, using only gray scale, the corpus callosum may not be evident.

• However, using color Doppler the pericallosal artery is a proof of its presence

15 6/7 weeks

The role of Gestational AgePericallosal Arteries

12 5/7 weeks17 1/7 weeks15 6/7 weeks

The role of Gestational AgePericallosal Arteries

Corpus Callosum

• Hypoechoic

• C-shaped

• Consistently seen after 18 wks

CSP

• Fluid filled space

• Consistently seen after 18 wks

Sonographic appearance of theCorpus Callosum & Cavum Septi Pellucidi

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Corpus callosum• The corpus callosum has several parts: the rostrum

(beak), genu (knee), corpus (trunk) and the splenium (tail)

RostrumRostrum

GenuGenu

CorpusCorpus

SpleniumSplenium

22 w22 w

Sonographic appearance of theCorpus Callosum

• Tail extends to quadrigeminal cistern (tectalplate)

22 w22 w

• The development of corpus callosum is closely associated with that of the CSP • There cannot be a CSP without

a covering corpus callosum•However, a corpus callosum

can be present in the absence of the CSP such as in septalagenesis as the result of SOD

EmbryologyCorpus Callosum & Cavum Septi Pellucidi

Cavum Septi Pellucidi

Cavum Vergae

22 w

Cavum septi pellucidi

Corpus callosum

(hypoechoic stripe)

The cava do not communicate with the ventricular systemThe cava do not communicate with the ventricular system

• The posterior space of the CSP is the cavum Vergae

• Prenatally CSP should normally be seen up to term

•Conditions associated with non-visualization of the CSP•Agenesis of the septa•Rupture 2dary to severe

hydrocephaly•Obliteration of the space

Non-visualization or echogenic Cavum Septi Pellucidi- does not

always equal AGCC

Malinger G et al. UOG 2012:40:165-70

NormalCSP

Echogenic CSP

When is Non-visualization of the Cavum SeptiPellucidi- not AGCC but Obliteration of the Space•Under direct visualization the entire corpus callosum

and pericallosal arteries are present.

•CSP appears echogenic

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• 23 fetuses with non-visualization or echogenic CSP without AGCC.• 17 fetuses apparent isolated anomaly• 6 fetuses associated with other findings

• Follow-up of 16 children at age 4-36 months• 14 children had normal development

• 1 child with childhood hypotonia; but normal milestones• 1 Mild motor and language delay

• Conclusion: Non-visualization of the CSP is not always associated with agenesis of the corpus callosum. When isolated it may be considered a variation of normal development.

Tectal Plate (Quadrigeminal Plate)

• It is the portion of the midbrain tectum upon which the superior and inferior colliculi sit.

•Corpus callosum reaches it

22 weeks

The tela choroidea of the 3rd ventricle (choroid plexus) covers the thalamus and the quadrigeminal plate

ThalamusThalamus

3rd Trimester Median Plane: Gyri & Sulci

34 weeks34 weeks

Cingulate sulcus (hyperechoic line)

Sulcus of the corpus callosum (hyperechoic line)

Cingulate gyrus (hypoechoic stripe)

Corpus callosum

(hypoechoic line)

Adult-like appearance of CC, CSP and Gyri & Sulci achieved during the 3rd trimester

• The use of color Doppler has been limited only in imaging the pericallosal arteries to confirm the presence of a normal corpus callosum.

Median Plane and Color Doppler Median Plane and Color Doppler

•Color/power Doppler reveals both the arterial and the venous system

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Veins, Arteries & Sinuses

•Can be differentiated by the anatomical location of the vessels.

Karl K et al Ultrasound of the Fetal Veins Part 3: The Fetal Intracerebral Venous System. Ultraschall Med 2016 Feb;37(1):6-26.

Internal cerebral vein

Transverse sinus Straight sinus

Superior sagittal sinus

Vein of Galen

Non-pulsatile flow

Triphasic

Doppler Flow Pattern

Can help differentiate between the different veins and sinuses.

Pericallosal a.

Callosomarginal a.

Anterior cerebral a.

Basilar a.

Arteries

Great vein of Galen Straight sinus

Superior sagittal sinus

Confluence of the

sinuses

Internal cerebral v

Transverse sinus

Veins & Sinuses

Vein of Galen• Located in the cistern of the velum interpositum and

quadrigeminal cistern

• Reconizable by the “kink”

• Located in the cistern of the velum interpositum and quadrigeminal cistern

• Reconizable by the “kink”

CSP

VermisVermis

Posterior Fossa

•Cerebellar Vermis•Cisterna

magna•4th ventricle•Fastigium

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Selected Brain Anomalies in Which the Median Plane Plays a Pivotal Role

in Diagnosis

•Disorders of the corpus callosum•Complete agenesis (absence)

• Tectal plate cysts•Cavum velli interpositi, Arachnoid cyst

•Vein of Galen aneurysm

• Thrombosis at the torcular

• It is typically suspected in the axial plane

•US findings are:•Non-visualization of the normal CSP•Ventriculomegaly ( > 10mm)

• In VM abnormalities of the corpus callosum seen in 13%*

• Incidence is 0.05 to 0.7%

Agenesis of the Corpus Callosum

*Li Y et al. Callosal dysgenesis in fetuses with ventriculomegaly: levels of agreement between imaging modalities and postnatal outcome. Ultrasound Obstet Gynecol. 2012 Nov;40(5):522-9

Agenesis of the Corpus Callosum

22 wk Normal

22 wk AGCC

•Absent• corpus callosum• cavum septi pellucidi• pericallosal artery

3D Diagnosis of AGCC

Tomographic Images AGCC Color Doppler & AGCC

Normal pericallosal artery

Interrupted pericallosal artery

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RightLeft

Tomographic Images AGCCOther findings: AGCC

•Midline interhemispheric cyst•Upwardly

displaced 3rd

ventricle• Most often seen in the

3rd trimester

38 wks

AGCC, Interhemispheric cyst and Dandy-Walker Malformation

•Absent corpus callosum & CSP• ≥ 25 wks absent CG, radial array of sulci in a ‘Sunburst’ appearance

AGCC Median Plane3rd Trimester

20-22 wks

Cavum Velum Interpositum (CVI) Cysts

• Median structure. Located anterior inferior to the splenium of the CC and superior to the telachoroidea of the 3rd

ventricle•Triangular in shape•Physiologic structures without clinical importance*

* Blasi I et al. J Ultrasound Med 2009; 28:683–687

Splenium of CC

Tela choroidea3rd ventricle

Arachnoid Cyst

• Could be associated with AGCC, absent CSP, cervical syringomielia, a Chiari malformation, and deficient cerebellar lobulation.

• Prognosis has been shown to be related to brain integrity

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* Blasi I et al. J Ultrasound Med 2009; 28:683–687

• Differential diagnosis CVI, arachnoid cyst, pineal tumors, hematoma, vein of Galen Malformation etc..

• Color Doppler aids in the diagnosis

Differential Diagnosis Median Cysts

Vein of Galen Aneurysm (VGAM)

•Median plane it appears as an anechoic elongated (sausage-shaped) cystic structure behind the corpus callosum and cavum septipellucidi• Color Doppler demonstrates turbulent flow

22 wksStraight sinus

V. Galen MalformationPericallosal a.

Corpus Callosum

• Is located in the cistern of velum interpositum and quadrigeminal plate cistern

•Drains through the straight sinus or embryonic falcine sinus.

Vein of Galen Aneurysm (VGAM)

Falcine sinus Straight sinus

Drains through the straight sinus or embryonic falcinesinus.

Vermis

Vermis

Vein of Galen Aneurysm (VGAM)Summary of findings

Karl K et al Ultrasound of the Fetal Veins Part 3:The Fetal Intracerebral Venous System. Ultraschall Med 2016 Feb;37(1):6-26.

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• Recent metanalysis of 34 studies, in which neonates accounted for 44%, infants 41% and children and adults for 12% of the sample showed that:

• Endovacular embolization results in acceptable mortality rates, complications and good clinical outcomes• 57% complete occlusion; 43% partial occlusion

• 68% good outcome• 31% poor outcome

• Post-embolization mortality & complications in 10%

Treatment VGAM

Yan J, et al. Outcome and complications of endovascular embolization for vein of Galen malformations: a systematic review and meta-analysis. J Neurosurg. 2015 Oct. 123 (4):872-90.

• Large supratentorial anechoic mass within it is a bright structure: a clot; may extend to straight sinus and vein of Galen• Color Doppler demonstrates no flow

20 wks

Thrombosis at the Torcular

Size: 3.92 x 1.94 cm

Corpus callosum Cavum septi pellucidi

Clot

Thrombosis at the Torcular – 39 wks

Schwartz N, Monteagudo A, Bornstein E et al . Thrombosis of an Ectatic TorcularHerophili: Anatomic Localization Using Fetal Neurosonography JUM 2008;27:989

Cerebellum Cerebellum Vermis

Tentorium

Thrombosis at the Torcular

Schwartz N, Monteagudo A, Bornstein E et al . Thrombosis of an Ectatic Torcular Herophili: Anatomic Localization Using Fetal Neurosonography JUM 2008;27:989

The superior sinus is displaced, pushed anteriorly by the thrombotic process

• In a recent review of 8 prenatally diagnosed cases Corral et al. found that:• Prenatal diagnosis has a predictable course,

with complete resolution without major neurologic sequelae in the majority of cases. • Normal outcome : 4 (50%)

• Speech disabilities: 3 (38%)

• Mild neurodevelopmental : 1 (13%)

• Ventriculomegaly is associated with an increased risk of neurodevelopmental delay.

Thrombosis at the Torcular

Corral e et a. Thrombosis of the torcular herophili in the fetus: a series of eight cases. Prenat Diagn 2014:34(12):1176-81

Summary & Conclusions

• Thank your for your attention.

• By routinely obtaining the median plane in all anatomical surveys (≥20 wks) you are taking the fetal neuroscan to a higher level.

• I hope, that I demonstrated that the median plane adds information when abnormalities are suspected on the axial plane. ie absent CSP

• … and it is a “must” in cases referred for a consultation due to a suspected anomaly.

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• Any Questions?Thank you for your attentionThank you for your attention