THREE DIMENSIONAL ULTRASOUND IN THE
EXAMINATION OF THE FETAL BRAIN

A study of the embryonic and foetal brain is a crucial phase of the ultrasound examination during pregnancy. Application of three-dimensional ultrasound in obstetrics began in 1989 volume acquisition and multiplanar rendering; successively (1991) with the increase in the use of “surface rendering” of the foetal facies.
In one of our studies, the use of three-dimensional rendering (3D) on 987 foetuses with physiological brain was of no diagnostic use in examining the foetal brain. In fact, it is not possible to obtain a three-dimensional reconstruction either of an individual encephalic structure or of the brain in toto. On the contrary, multiplanar ultrasound (MP-rendering) turned out to be the method of choice for an analysis of the foetal brain as it allowed for the following:

- Selection of sagittal and frontal planes, difficult to obtain in free-hand B-Mode;
- Visualisation of brain structures otherwise difficult to study in free-hand B-Mode;
- Multiplanar comparison of individual brain structures on the 3 orthogonal scans by using the stereotaxic voxel (marker dot).


Ultrasound scans available for ultrasound signal evaluation in
B-Mode vs. V-Mode (Volume-Mode).


Brain Structures Visible in echo B-Mode (2D)

1. Interhemispheric fissure
2. Cavum septi pellucidi (CSP)
3. Third ventricle (3V)
4. Thalami
5. Lateral ventricles: Anterior and posterior horns
6. Cerebellum
7. Cisterna magna
8. Sylvian fissure

More rarely

9. Fourth ventricle
10. Corpus callosum (CC): Percentage of visualisation 5%

Brain Structures Visible in Volume-Mode (multiplanar ultrasound or MP-rendering):

1. Interhemispheric fissure
2. Cavum septi pellucidi (CSP)
3. Third ventricle (3V)
4. Thalami
5. Lateral ventricles: Anterior and posterior horns
6. Cerebellum
7. Cisterna magna
8. Sylvian fissure
9. Fourth ventricle
10. Corpus callosum (CC): Percentage of visualisation 92%
11. "Architecture" of relation between CC. CSP and 3V
12. Sylvian aqueduct
13. Area of fornix and choroid plexus of the 3rd ventricle
14. Mesencephalon
15. Lamina quadrigemina
16. Cingulate gyrus (GC - cingulate scissure)
17. Brainstem (medulla, pons e mesencephalon)
18. Area of tubercola quadrigemina and epiphysis
19. Early foetal brain structures (Study in progress with Prof. Laurini, University of Lausanne)


EXAMPLES OF BRAIN STRUCTURES VISIBLE IN MP ULTRASOUND: REFORMATTED SAGITTAL AND FRONTAL SCAN


The legend is reported in Fig. 12a.

 

 

Pregnancy at 21st week gestation. Trans- abdominal multiplanar ultrasound compared with a physiologic post-mortem specimen. In A is selected the sagittal scan obtained by computed re-format processing: red arrows point the same structures which are reported in the scheme.
1 = mesencephalon; 2 = pons; 3 = medulla; 4 = cerebellum; 5 = lamina quadrigemina; 6 = epiphysis; 7 = cingulate gyrus; 8 = corpus callosum (corpus); 9 = corpus callosum (rostrum); 10 = fornix; 11 = interthalamic area – 3rd ventricle; 12 = 4th ventricle; 13 = aqueduct of Silvius; 14 = epiphyseal peduncle; 15 = cisterna magna; 16 = tela choroidea; 17 = cavum septi pellucidi.

 

 

 

Same case as in previous movie compared with an autoptic specimen. The image is magnified and different grey-scale tones are selected in order to put in evidence the epiphysis. Caption is the same of precedent Movie.

 

An expert sonographer can ascertain whether a physiologic foetal brain is normal in 30-40 seconds, using a test in B-Mode: In these cases, the multiplanar option may be of little use for a routine brain exam, however, we believe it important for the operator to have knowledge of the morphology of the structures that can be seen on the little familiar sagittal and frontal planes, their spatial architecture and the multiplanar comparison technique in MP-rendering, so that he may recognize any alterations undergone by these structures in pathologic conditions (Our group: Multiplanar Ultrasound in the examination of physiologic brain. Abstract from the World Congress on Ultrasound Procedures ISUOG 2002 - New York - In Press).
The scientific community should consider and evaluate the need to introduce a second level exam for the pathologic or suspected pathologic brain (Table 2), using multiplanar ultrasound, just as introduced a while ago for the foetal heart (Iaccarino M. Sciaudone G. et al, Ferrara - 2001).

 


Illustration of possible use of multiplanar ultrasound as a tool for second level inquiries in the study of the pathologic or suspected pathologic foetal brain (Our group: Multiplanar Ultrasound in the examination of the foetal brain affected by Dandy Walker malformation: New ultrasonographic signs useful for postnatal prognosis - Speech Presentation before the World Congress on Ultrasound Procedures ISUOG 2002 - New York - In Press).




Fisiologia

Fig. 1a. Illustration of the 3 planes (transversal, frontal and sagittal) used to examine the foetal encephalon.

Fig. 1b. Illustration of various transversal sections of the encephalus available from bidimensional ultrasound.

Fig. 1c. Complete diagram showing transversal and frontal planes used to scan the foetal encephalus in B-Mode.

Fig. 1d. Sagittal foetal section of physiologic foetal brain during 28th week of pregnancy.

Fig. 1e. Same as preceding case. Structure of the posterior cranial fossa.

Fig. 1f. Comparison between physiologic pregnancy on 21st week and post-mortem anatomical findings during same period.

Fig. 2a. Pregnancy at 12th week gestation. 3D ultrasound. Physiologic encephalon: trans-abdominal examination.

Fig. 2b. 3D ultrasound. Same as preceding case without markers.

Fig. 2c. 3D ultrasound. Same as preceding case. Note cerebellum biometry of the latero-lateral diameter (10.1mm).

Fig. 3a. Pregnancy at 13th week gestation. 3D ultrasound. Trans-vaginal volume. Multiplanar ultrasound. Physiologic foetal brain.

Fig. 3b. 3D ultrasound. Same as preceding case without markers.

Fig. 4a. Pregnancy at 16th week gestation. 3D ultrasound. Multiplanar ultrasound. Physiologic foetal brain examined by trans-vaginal volume.

Fig. 4b. 3D ultrasound. Same as preceding case. The stereotaxic voxel (marker dot) is in the CSP.

Fig. 4c. 3D ultrasound. Same as preceding case. The stereotaxic voxel (marker dot) is positioned in correspondence with the 3rd ventricle.

Fig. 5. Pregnancy at 17 weeks, 6 days gestation.3D ultrasound. Trans-abdominal volume. Multiplanar ultrasound. Physiologic brain.

Fig. 6. 3D ultrasound. Same as preceding case: The stereotaxic voxel (marker dot) is located on the CSP.

Fig. 7. 3D ultrasound. Same as preceding case: Magnification of some details.

Fig. 8. 3D ultrasound. Same as preceding case. The stereotaxic voxel (marker dot) (or marker dot) points to the cerebellum .


Fig. 9. Pregnancy at 28th week gestation. 3D ultrasound. TA multiplanar rendering. Arrows indicate the cerebellar hemispheres and the cerebellar vermis in a physiologic case.



Fig. 10. Pregnancy at 21st week gestation. 3D ultrasound. Frontal trans-cerebellar scan is used to exclude partial agenesis of the vermis.

Fig. 11. 3D ultrasound. Same as preceding case without markers.

Fig. 12a. Pregnancy at 27th week gestation. 3D ultrasound. Volume-Mode. Multiplanar ultrasound. Physiologic foetal brain. The stereotaxic voxel (marker dot) is located in the third ventricle.


Fig. 12b. 3D ultrasound. Same case and same image as preceding, without markers.

Fig. 12c. Pregnancy at 27th week gestation. 3D ultrasound. Trans-abdominal volume. Physiologic foetal brain. The stereotaxic voxel (marker dot) is located on the cavum septi pellucidi.

Fig. 12d. Pregnancy at 23rd week gestation. Foetal brain. Lateral view.

Fig. 12e. Median sagittal section of the brain, in toto.

Fig. 12f. Post-mortem examination of foetal brain at 24th week. Trans-ventricular and trans-thalamic section.


Fig. 13. Pregnancy at 32nd week gestation.3D ultrasound. Multiplanar ultrasound.of physiologic encephalon. On sagittal scan the corpus callosum is highlighted by the red arrows


Fig. 14. Same as preceding case. 3D ultrasound. The stereotaxic voxel indicates the CSP.


PATHOLOGIES OF POSTERIOR CRANIAL FOSSA


Fig. 15a. Pregnancy at 23rd week gestation. 3D ultrasound. Multiplanar ultrasound. Complete agenesis of cerebellar vermis (complete Dandy-Walker).


Fig. 15b. Pregnancy at 20th week gestation.3D ultrasound. Multiplanar ultrasound. Foetus affected by serious cystic hygroma associated with complete Dandy-Walker.




Fig.16a. Pregnancy at 18th week gestation. 3D ultrasound. Foetus affected by Dandy Walker variant.


Fig. 16b. Same as preceding case and same volume. 3D ultrasound. The stereotaxic voxel (marker dot) now points to 4th dilated ventricle.


Fig. 17a. Pregnancy at 23rd week gestation. 3D ultrasound. Arachnoid cyst of posterior cranial fossa. Confirmed at birth.


Fig. 17b. Pregnancy at 33rd week gestation. 3D ultrasound. Multiplanar ultrasound. Arachnoid cyst in posterior cranial fossa.


Fig. 17c. 3D ultrasound. Same case and same image as preceding illustration, without markers.


Fig. 17d. 3D ultrasound. Same as preceding case with stereotaxic voxel (marker dot) on enlarged 3rd ventricle.


Fig. 17e. 3D ultrasound. Same case and same image as preceding illustration, without markers.


Fig. 18a. Pregnancy at 23rd week gestation. 3D ultrasound. 3 orthogonal scans. Cerebellar infarction.


Fig. 18b. 3D ultrasound. Same as preceding case. In A, note the CC (red arrows), the CSP (green arrow) and hypo-echoic area, located underneath the CSP, at height of 3rd ventricle


Fig. 19a. Pregnancy at 21st week gestation. 3D ultrasound. Foetus affected by Chiari II examined by multiplanar ultrasound: Massive cerebral prolapse.



Fig. 19b. Post-mortem examination of pregnancy at 21 week gestation. Foetus affected by malformation, type Chiari II.


Fig. 19c. Same as preceding case upon completion of rachis and cranial removal.


Fig. 19d. Foetal brain at 21st week of pregnancy affected by Chiari II malformation. Lateral view highlights prolapse of cerebellum toward the rachis.


Fig. 19e. Post-mortem examination of normal brain at 21st week of pregnancy for comparison with following illustration of pathologic foetus affected by Chiari II


Fig. 19f. Post-mortem examination of foetus affected by Chiari II: coronal section.



PATHOLOGIES OF MEDIAL CRANIAL FOSSA


Fig. 20a. Pregnancy at 23rd week.3D ultrasound. Multiplanar ultrasound. Agenesis of corpus callosum. The stereotaxic voxel (marker dot) is located in the third ventricle.


Fig. 20b. Pregnancy at 23rd week gestation. 3D ultrasound. Multiplanar ultrasound. Agenesis of corpus callosum. The stereotaxic voxel (marker dot) is located in the fourth ventricle


Fig. 20c. Same case as in previous figure and same volume. 3D ultrasound. Multiplanar ultrasound. Agenesis of the corpus callosum.


Fig. 20d. 3D ultrasound. Same as preceding case. Measurement of posterior horn. Size greater than anterior horn.


Fig. 21. Pregnancy at 28th week gestation. 3D ultrasound. TA ultrasound. Multiplanar rendering. Cyst of cavum septi pellucidi.



HYDROCEPHALUS

Fig. 22. Pregnancy at 20th week gestation. 3D ultrasound. Trans-abdominal volume. Hydrocephalus examined by multiplanar rendering on sagiptal scan.




Fig. 23a. Pregnancy at 25th week gestation. 3D ultrasound. Trans-abdominal volume. Multiplanar rendering. Hydrocephalus. The stereotaxic voxel (marker dot) is placed in 3rd ventricle.

Fig. 23b. 3D ultrasound. The preceding illustration repeated here without markers.

Fig. 23c. Same as preceding case, same volume differently reformatted. 3D ultrasound. Stereotaxic voxel (marker dot) positioned in CSP. 1 = CSP.

Fig. 24a. Pregnancy at 25th week gestation. 3D ultrasound. Trans-abdominal volume. Multiplanar ultrasound. Hydrocephalus.

Fig. 24b. Same as preceding case and same volume differently reformatted. 3D ultrasound. The stereotaxic voxel (marker dot) is positioned in the CSP.