Isolated choroid plexus separation on second-trimester sonography: natural history and postnatal importance

The developing brain by trimester

Transient anatomical entities play a role in the maturation of brain regions and early functional fetal networks. At the postmenstrual age of 7 weeks, major subdivisions of the brain are visible. At the end of the embryonic period, the cortical plate covers the neopallium. The choroid plexus develops in concert with it, and the dorsal thalamus covers about half the diencephalic third ventricle surface. In addition to the fourth ventricle neuroepithelium the rhombic lips are an active neuroepithelial production site. Early reciprocal connections between the thalamus and cortex are present. The corticospinal tract has reached the pyramidal decussation, and the arteries forming the mature circle of Willis are seen. Moreover, the superior sagittal sinus has formed, and at the rostral neuropore the massa commissuralis is growing. At the viable preterm age of around 24 weeks PMA, white matter tracts are in full development. Asymmetric progenitor division permits production of neurons, subventricular zone precursors, and glial cells. Myelin is present in the ventral spinal quadrant, cuneate fascicle, and spinal motor fibers. The neopallial mantle has been separated into transient layers (stratified transitional fields) between the neuroepithelium and the cortical plate. The subplate plays an important role in organizing the structuring of the cortical plate. Commissural tracts have shaped the corpus callosum, early primary gyri are present, and opercularization has started caudally, forming the lateral fissure. Thalamic and striatal nuclei have formed, although GABAergic neurons continue to migrate into the thalamus from the corpus gangliothalamicum. Near-term PMA cerebral sublobulation is active. Between 24 and 32 weeks, primary sulci develop. Myelin is present in the superior cerebellar peduncle, rubrospinal tract, and inferior olive. Germinal matrix disappears from the telencephalon, except for the GABAergic frontal cortical subventricular neuroepithelium.

Evaluation of choroid plexus with fetal magnetic resonance imaging: What happens in ventriculomegaly?

OBJECTIVES

Diagnosis of ventriculomegaly (VM) and identification of choroid plexus (CP) can be challenging with fetal magnetic resonance imaging (MRI). Our aim is to create an adjunct method for supporting the diagnosis of VM by investigating the CP-ventricular wall separation distance in fetuses with and without VM (nV) with fetal MRI.

METHODS

T2-weighted fetal MRIs of 154 fetuses were retrospectively evaluated. The CP separation was defined as the distance between the medial wall of the dependent ventricle and distal tip of the CP glomus. The measurement was performed at the same plane with the dependent ventricle measurement by two blinded readers.

RESULTS

41 fetuses with VM (mean gestational age 27 (19-35 weeks), and 44 nV fetuses (mean gestational age 28 (20-39 weeks) were included. Interobserver reliability was excellent for ventricle diameters (R = 0.99, confidence interval (CI) 95%) and the separation of CP (R = 0.98, CI 95%). Mean distance of CP separation was 10.7 mm ± 4.2 mm and 3.0 ± 1.6 mm in VM and nV fetuses, respectively (p < 0.001). The distance of CP separation to differentiate VM cases was 6.5 mm (sensitivity: 0.98, specificity: 0.98). Separation of CP was correlated to ventricle diameter in cases with (R = 0.674) and without VM (R = 0.805). For the cut-off value >0.65 cm for the distance between the medial wall of the dependent ventricle and the medial border of choroid plexus sensitivity is 97.56, specificity 95.45, positive predictive value (PPV) 95.20, negative predictive value (NPV) 97.70, and likelihood ratio (LR) (+) is 21.46.

CONCLUSION

Fetal CP can be efficiently evaluated with MRI, and the increase of CP-ventricular wall separation distance in correlation with the ventricle diameter is a reliable sign in the diagnosis of fetal VM.

Fetal cerebral ventricular atria width of 8-10mm: A possible prenatal risk factor for adolescent treated Attention Deficit Hyperactivity Disorder (ADHD)

The purpose of our research was to study the in-utero and long term post-natal outcome of fetal isolated cerebral ventricular atria width between 8 and 10mm. We conducted a retrospective, observational, case-control study, of low risk pregnant women, between 1993 and 2001. One hundred and forty one fetuses with isolated cerebral ventricular atria width between 8 and 10mm, corresponding to 2-4 standard deviations above the mean, and 309 controls, with atrial width below this level, were included for the analysis. Clinical data concerning pre and post-natal outcome was retrieved from computerized medical records. Matching of cases with controls was based on age, with a ratio of 2-3 controls per case. Statistical analysis included: T-test, Chi-Square, and Multiple Logistic Regression analysis. The study group was characterized by a predominance of male gender, left side involvement, and higher birth weight, compared to the control group. Long term post-natal follow-up at a mean age of 12.7 years (±1.9) demonstrated an adjusted odds ratio of 2.589 (95% CI 1.415-4.737, p=0.001), being diagnosed as Attention Deficit Hyperactivity Disorder (ADHD), and treated by Methylphenidate (Ritalin(®)), during childhood, compared to the control group (23.6% and 10.0% respectively) (p=0.001). Cerebral atria width was an independent factor, controlled for the only two significant variants between groups, gender and weight over 90th centile. In conclusions, our preliminary results show that fetuses with prenatal finding of isolated cerebral ventricular atria width between 8 and 10mm are more likely of being diagnosed and treated as ADHD during childhood.

Choroid plexus separation in fetuses without ventriculomegaly: Natural course and postnatal outcome

PURPOSE

To evaluate fetuses with choroid plexus separation without ventriculomegaly in terms of fetal malformations, behavior of the separation during follow-up, and postnatal outcome.

METHODS

In total, 172 fetuses with choroid plexus separation without ventriculomegaly were included in this prospective study. Fetal sonography was performed at 2- to 4-week intervals, and detailed physical and neurologic examinations were performed after their delivery. Fetuses were categorized into normal and abnormal subgroups according to the outcome.

RESULTS

Sixteen fetuses (9.3%) were included in the abnormal-outcome group and 156 fetuses (90.7%) were included in the normal-outcome group. Both the initial mean lateral ventricular diameter (9.3 mm versus 8.6 mm) and the initial mean choroid plexus separation (4.8 mm versus 3.3 mm) were greater in the abnormal group than in the normal group (p < 0.001 for both comparisons). We found that 4.0 mm was the best cutoff point of choroid plexus separation to detect a major anomaly, with 87.5% sensitivity and 93.6% specificity.

CONCLUSIONS

Choroid plexus separation without ventriculomegaly often resolves within the third trimester and does not affect postnatal outcome. It can be associated with various fetal malformations; however, with a comprehensive examination, all fetal malformations can be detected prenatally. Follow-up sonography studies would be useful, especially in the case of suspected corpus callosum agenesis.

Bifid choroid plexus: always a normal fetal brain structure variant?

Choroid plexus, a fetal organ developing approximately from the sixth week of gestation, plays a fundamental role in developing fetal brain organization. As relatively little is known about the relationship between anomalies of choroid plexuses structure and their role in brain function, we examined cases of bifid choroid plexus (BCP) and discussed their potential association with lateral ventriculomegaly, other abnormal ultrasound findings, and their potential role as markers of fetal chromosomal abnormalities. In the present study, we described 23 cases of fetal BCP found in 2145 routine second trimester ultrasounds. For each patient 2D and 3D ultrasound volumes were acquired. BCP was defined as a choroid plexus whose body was divided into two portions (arms) differently located and oriented on the three spatial axes in correspondence to the lateral ventricle, in one or both sides. The entity of the separation and reciprocal orientation of the two arms was examined. The presence of BCP in a low-risk population of pregnant women undergoing routine second trimester ultrasound was showed. Lateral ventricles significantly increased in the presence of BCP. Malformations were found in four of 23 fetuses with BCP. Pregnancy outcome was favorable only in one of these four cases. We suggest that in the presence of mono or bilateral BCP without associated abnormal ultrasound findings, a closer look at fetal brain or extra-cranial structures is recommended. If no related abnormalities are found, serial prenatal and postnatal sonographic follow-up should be considered. In the presence of concomitant abnormal findings, genetic counseling, fetal karyotyping and magnetic resonance imaging, if possible by gestational age, are strongly advised.

Detailed ultrasound screening in the second trimester: pictorial essay of normal fetal anatomy

Today, ultrasound is the main diagnostic tool in the prenatal detection of congenital abnormalities. Therefore, ultrasound examination should be offered to all pregnant women. A detailed sonographic examination of the fetus is usually performed between 18 and 22 weeks of pregnancy. The accurate recognition of normal fetal anatomy is very important for the detection of both minor and major defects. The purpose of this pictorial essay is to show fetal anatomic structures, which have to be examined between the 18(th) and 22(nd) weeks of pregnancy, and present their standard measurements systematically and thoroughly in accordance with sonographically obtained ideal sections.

Normal sonographic development of the central nervous system from the second trimester onwards using 2D, 3D and transvaginal sonography

The developmental changes of the fetal central nervous system (CNS) during the second and third trimesters, specifically the brain, relate mostly to changes in size. However, other changes do occur in the fetal brain during the second and third trimester such as: the union of the cerebellar hemispheres, development of the corpus callosum (CC), and increasing complexity of the cerebral cortex. These changes follow a well-defined developmental timeline recognizable by sonography. The fetal neuroscan can be divided into a 'basic scan' which is performed transabdominally and a 'targeted Exam or neurosonogram' which uses a multiplanar approach, which preferably should be performed transvaginally. During the 'basic scan', several brain structures are imaged in addition to obtaining important biometric measurements. The 'neurosonogram' is a more extensive or detailed fetal study during which the emphasis is on the addition of coronal and sagittal planes. The easiest way to obtain these planes, if the fetus is in a cephalic presentation, is the transvaginal route. Three-dimensional (3D) sonography should, if possible, be performed transvaginally using the multiplanar approach. An added benefit of 3D sonography is the ability to display and render the volume in a variety of ways which may enhance the detection of pathology.