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Measurement of the cerebral lateral ventricles: It has changed!

Monash Health Advanced Obstetric Ultrasound Update

Joyce Chen

Overview

• Ventriculomegaly (VM)• What is it?• Why is it important?

• Ultrasound assessment• What does the literature say?• Inconsistencies in the literature• An alternative measurement landmark

• Suggestions for clinical practice

Ventriculomegaly

• Abnormal dilatation of the ventricular system (Chiu et al., 2014)

• Common anomaly affecting 0.7-1% of pregnancies (Prayer et al., 2019)

• Requires further investigation• Many associations

• Infection• Aneuploidy• Genetic syndromes• Structural malformations

• Isolated

Ventriculomegaly

• Wide spectrum of postnatal outcomes• Not well reported• Normal• Severe neurological disability or death

• Prognosis depends on presence of coexisting abnormalities• Rate of additional abnormalities detected appears to be

proportional to severity of VM (Hannon et al., 2012)

• 50% of fetuses with severe VM were found to have additional anomalies

• 2014 meta-analysis suggests favourable outcomes for mild VM (Pagani et al., 2014)

Ultrasound criteria

Mild Moderate Severe

10 – 12 mm 12.1 – 14.9 mm ≥ 15 mm

• Based on the diameter of the atrium• Atrium is the confluence of the body, occipital and temporal horns

ISUOG 2007 Guidelines

• Ultrasound measurement technique• Transventricular plane • Across the choroid plexus glomus • Inner-to-inner caliper placement• Perpendicular to long axis of ventricle

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Technique pitfalls

• Susceptible to intra- and inter-observer variability • Variable location and shape of the choroid plexus

• Planes and caliper placement used to obtain measurements may vary

• Difficult visualisation of near-field ventricle

MFM 2018 Statement

Fox et. al., 2018International Society of Ultrasound in Obstetrics and Gynaecology., 2007

MFM 2018 Statement An alternative measurement landmark: Parieto-Occipital Fissure

• Guibaud et. al suggested to measure at the POF instead of choroid plexus glomus • Fixed landmark• Easily visualised

• Strict criteria to ensure correct plane and reproducible measurements

Parieto-Occipital Fissure

• Located at convergence of the parietal and occipital lobes

• According to Guibaud, this landmark defines the atrium (Guibaud., 2009)

21 weeks

Toi A, Lister WS, Fong KW. How early are fetal cerebral sulci visible at prenatal ultrasound and what is the normal pattern of early fetal sulcal development?

Ultrasound Obstet Gynecol 2004; 24: 706– 715.

Parietal Lobe

Occipital Lobe

Parieto-Occipital Fissure

• On ultrasound:

• Seen from 18 weeks

• Protrusion on the inner border of the hemisphere

• Becomes deeper with advancing gestation

• Triangular - apex pointing away from the midline

21 weeks

POFCSP

Choroid Plexus Atrium

Occipital horn

25 weeks

POF

32 weeks

POF

36 weeks

POF

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Rule 3

Rule 2

Rule 1

Magnification:

• Image occupies entire screen• Both calvarial margins are included

Strict Axial plane:

• Midline falx cerebri is equidistant from the near- and far-field calvarium

• Off axis → oblique measurement through atrium → overestimation of atrial width

• Midline falx perpendicular to ultrasound beam

• Increases reflection of ventricular wall → helps with correct caliper placement

Measuring at the parieto-occipital fissure: Technical requirements

Rule 5

Rule 4

Measuring at the parieto-occipital fissure: Technical requirements Anatomical landmarks on the Transventricular plane :

• Anteriorly – Cavum septum pellucidum or fornix columns• Posteriorly – V-shaped cistern of the great cerebral veins (ambient

cistern)

• Persistently identifiable if at correct trans-ventricular axial plane

Caliper placement:

• Level of the deepest part of the parieto-occipital fissure• Perpendicular to ventricular cavity• Placed on the junction of the ventricular lumen and ventricular wall

Near field ventricle

• Magnification

• Axial plane: Falx equidistant

• Transducer orientation: Falx 30 degrees away from horizontal axis• Reduces reverberation artefact from bony calvarium

• Anterior landmark: CSP

• Posterior landmark: Parietal-Occipital Fissure

• Calipers: Inner-to-inner perpendicular to ventricular wall

Keep in mind…

• 10 mm threshold was first established more than 30 years ago

• References ranges have been determined based on measurements obtained across the choroid plexus glomus

Case study

36 weeks 36 weeks24 weeks 24 weeks

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Third trimester example

36 weeks 36 weeks

In summary

• Measure at the POF • Be aware that data is based on different

measurement landmark

• Routinely assess near- and far-field ventricles

References • CHIU, T.-H., HALIZA, G., LIN, Y.-H., HUNG, T.-H., HSU, J.-J., HSIEH, T. S.-T. A. & LO, L.-M. 2014. A retrospective study on the course and outcome of fetal ventriculomegaly. Taiwanese Journal of Obstetrics and Gynecology, 53, 170-177.

• PRAYER, D., PALADINI, D. & DEPREST, J. 2019. Current Controversies in Prenatal Diagnosis 1: Should MRI be performed on all fetuses with mild ventriculomegaly? Prenatal Diagnosis, 39, 331-338.

• FOX, N. S., MONTEAGUDO, A., KULLER, J. A., CRAIGO, S. & NORTON, M. E. 2018. Mild fetal ventriculomegaly: diagnosis, evaluation, and management. American Journal of Obstetrics and Gynecology, 219,B2-B9.

• GAGLIOTI, P., OBERTO, M. & TODROS, T. 2009. The significance of fetal ventriculomegaly: etiology, short- and long-term outcomes. Prenatal Diagnosis, 29, 381-388.

• INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2007. Sonographic examination of the fetal central nervous system: guidelines for performing the ‘basic examination’ and the ‘fetal neurosonogram’. Ultrasound in Obstetrics & Gynecology, 29, 109-116.

• KANDULA, T., FAHEY, M., CHALMERS, R., EDWARDS, A., SHEKLETON, P., TEOH, M., CLARK, J. & GOERGEN, S. K. 2015. Isolated ventriculomegaly on prenatal ultrasound: What does fetal MRI add? Journal of Medical Imaging and Radiation Oncology, 59, 154-162.

• LASKIN, M. D., KINGDOM, J., TOI, A., CHITAYAT, D. & OHLSSON, A. 2005. Perinatal and neurodevelopmental outcome with isolated fetal ventriculomegaly: A systematic review. The Journal of Maternal-Fetal & Neonatal Medicine, 18, 289-298.

• GUIBAUD, L. 2009. Fetal cerebral ventricular measurement and ventriculomegaly: time for procedure standardization. Ultrasound in Obstetrics and Gynecology, 34, 127-130.• ALONSO, I., BORENSTEIN, M., GRANT, G., NARBONA, I. & AZUMENDI, G. 2010. Depth of brain fissures in normal fetuses by prenatal ultrasound between 19 and 30 weeks of gestation. Ultrasound in Obstetrics & Gynecology, 36, 693-699

• PAGANI, G., THILAGANATHAN, B. & PREFUMO, F. 2014. Neurodevelopmental outcome in isolated mild fetal ventriculomegaly: systematic review and meta-analysis. Ultrasound in Obstetrics & Gynecology, 44, 254-260.