Abnormal prenatal sonographic findings in the posterior cranial fossa: a case of Joubert's syndrome

Quantitative diagnostic advantages of three-dimensional ultrasound volume imaging for fetal posterior fossa anomalies: Preliminary establishment of a prediction model

OBJECTIVES

To quantitatively assess prenatal diagnostic performance of three-dimensional ultrasound (3D-US) for posterior fossa anomalies (PFA) and establish a preliminarily 3D-US prediction model.

METHODS

Sixty singleton fetuses suspected of PFA by 2D-US presented their detailed 3D-US evaluation. The surface area of vermis (SAV), brainstem-vermis, and brainstem-tentorium angles were measured by 3D-US. The good prognosis was defined as normal neurodevelopmental outcome. MRI and autopsy were the diagnostic reference standard.

RESULTS

There was a significant difference between 2D-US (60.0%, 36/60) and 3D-US (94.8%, 55/58) for the diagnostic accuracy (P < .01). Prenatal 3D-US prediction model was established with observed/expected SAV as the main predictor (area under the curve [AUC]: 0.901; 95% CI, 0.810-0.992, P < .001). When it was more than 107.5%, the prognosis seemed to be good (sensitivity: 96.4%, specificity: 26.7%), which led to consideration of mega cisterna magna, Blake pouch cyst, or small arachnoid cyst. The prognosis appeared to be poor when it was less than 73% (sensitivity: 71.4%, specificity: 100%), and the diagnosis tended to be a Dandy-Walker malformation, vermian hypoplasia, and cerebellar hypoplasia. Brainstem-vermis and brainstem-tentorium angles were the secondary indicators (AUC: 0.689 vs 0.761; 95% CI, 0.541-0.836 vs 0.624-0.897, P = .014 vs.001).

CONCLUSIONS

It seems that the exact types of PFA can be effectively diagnosed by quantitative indicators of 3D-US.

Diagnostic imaging of posterior fossa anomalies in the fetus and neonate: part 2, Posterior fossa disorders

This second portion of a two-part review illustrates examples of posterior fossa disorders detectable on prenatal ultrasound and MRI, with postnatal or pathology correlation where available. These disorders are discussed in the context of an anatomic classification scheme described in Part 1 of this posterior fossa anomaly review. Assessment of the size and formation of the cerebellar hemispheres and vermis is critical. Diagnoses discussed here include arachnoid cyst, Blake's pouch cyst, Dandy-Walker malformation, vermian agenesis, Joubert syndrome, rhombencephalosynapsis, Chiari II malformation, ischemia, and tumors.

Cisterna magna width at 11-13 weeks in the detection of posterior fossa anomalies

OBJECTIVE

To construct reference ranges for cisterna magna (CM) width at 11-13 weeks' gestation in healthy fetuses and determine whether open spina bifida and posterior fossa anomalies could be diagnosed in the first trimester.

METHODS

This was a retrospective study. CM width reference ranges were constructed based on the measurements obtained from 80 healthy fetuses with normal postnatal outcome undergoing routine first-trimester ultrasound at 11-13 weeks, using the Lambda-Mu-Sigma method. CM was measured in the fetal mid-sagittal view, as routinely used for nuchal translucency assessment. In addition, first-trimester ultrasound images in 11 fetuses with open spina bifida or posterior fossa anomalies, most of which were diagnosed later in pregnancy, were retrospectively reviewed, and CM measurements were compared against reference ranges.

RESULTS

CM width was noted to increase with gestational age in normal fetuses. The anomalies in the 11 fetuses we reviewed were: open spina bifida (n = 5), megacisterna magna (n = 3), Blake's pouch cyst (n = 2) and posterior fossa arachnoid cyst (n = 1). All fetuses with open spina bifida had a CM width below the 5(th) percentile. In the two fetuses with Blake's pouch cyst and in two with megacisterna magna, CM width was above the 95(th) percentile. In one of the fetuses with a megacisterna magna and the one with an arachnoid cyst, CM width was within normal range.

CONCLUSION

We have constructed reference ranges for CM width at 11-13 weeks using the mid-sagittal view. It appears that first-trimester CM width can be used as a marker for the early detection of open spina bifida. However, our findings need to be confirmed in prospective large series.

Role of MR imaging in prenatal diagnosis of pregnancies at risk for Joubert syndrome and related cerebellar disorders

BACKGROUND AND PURPOSE

JSRD are rare autosomal recessive brain malformations. We hypothesized that MR imaging can assess fetuses at risk for JSRD and might influence their diagnoses.

MATERIALS AND METHODS

We prospectively performed cranial MR imaging for 12 fetuses (mean GA, 23 weeks; SD, 3.7) at 25% recurrence risk for JSRD. We correlated prenatal MR imaging findings with postnatal MR imaging and clinical outcome. Retrospectively, we compared posterior fossa measurements of the cases with those of 24 age-matched fetuses with proved normal brain MR imaging. Institutional review board approval and consents were obtained. Statistical methods included a t test and ANCOVA tests.

RESULTS

Fetal MR imaging correctly diagnosed 3 cases at 22, 28, and 29 weeks of gestation as JSRD, and 9 cases as normal. In JSRD-affected fetuses, prenatal MR imaging detected narrow pontomesencephalic junction (isthmus) with deepening of the interpeduncular fossa and thick horizontally placed superior cerebellar peduncles (MTS), deformed anteriorly convex floor of the fourth ventricle, and midline cerebellar cleft in place of the hypoplastic vermis. Measurements on axial fetal MR imaging at pontomesencephalic junction, ratio of AP diameters of interpeduncular fossa to midbrain/isthmus, and ratio of the AP to transverse diameters of the fourth ventricle were significantly higher in JSRD-affected fetuses than in nonaffected cases and the control group.

CONCLUSIONS

MR imaging can diagnose JSRD in at-risk pregnancies by detecting posterior fossa signs. Measurements at the pontomesencephalic junction may enhance fetal MR imaging accuracy in diagnosing JSRD.

Sonographic measurements of the fetal fastigium between 20 and 40 weeks' gestation

OBJECTIVE

The purpose of this study was to establish a new reference angle chart for fastigial biometric measurements throughout gestation in normal singleton pregnancies.

METHODS

A prospective cohort study was designed. A total of 505 pregnant women between 20 and 40 weeks' gestation were included in the study. Excluded were those with multiple pregnancies, congenital anomalies, abnormal karyotypes, and polyhydramnios or oligohydramnios. Transvaginal or transabdominal sonography was performed in the midsagittal plane of the brain.

RESULTS

The angle of the fastigium was found to be 30 degrees to 60 degrees throughout pregnancy. These data were found to be constant during the progression of pregnancy without any significant changes.

CONCLUSIONS

Fastigial measurements throughout pregnancy are presented. Its angle is constant throughout pregnancy. Evaluation of the fastigium may assist in cases of subtle posterior fossa anomalies.

Prenatal ultrasonographic features of Joubert syndrome

We describe the prenatal imaging of 2 fetuses at risk for Joubert syndrome (JS). In the first case, the mother, who had previously given birth to a child with JS, was referred to our hospital at 17 weeks' gestation. The prenatal diagnosis of JS complicated with an encephalocele was made. In the second case, the mother had previously given birth to 2 children with JS. A diagnosis of JS complicated with postaxial polydactyly of the right foot was made. In both cases, the pregnancy was terminated following genetic counseling. Postmortem examinations confirmed the diagnosis of JS.

The fetal cerebellar vermis: anatomy and biometric assessment using volume contrast imaging in the C-plane (VCI-C)

OBJECTIVES

To describe the normal appearance and study the biometry of the fetal cerebellar vermis by three-dimensional (3D) volume contrast imaging in the coronal (C-) plane (VCI-C).

METHODS

A total of 203 normally developed fetuses were examined prospectively at 18-33 weeks' gestation. At the level of the view used to measure the transverse cerebellar diameter (TCD), a VCI-C plane was displayed to examine, using a transabdominal probe, the fetal mid-saggital vermis. The volumes acquired were stored for later review and measurement of the anteroposterior (AP) diameter, craniocaudal (CC) diameter and surface area of the cerebellar vermis. Each dataset was evaluated by two independent observers. Measurements as a function of gestational age (GA), biparietal diameter (BPD), head circumference (HC) and TCD were expressed by regression equations. Interobserver variability was evaluated. Nomograms were produced. In order to validate the use of VCI in fetal biometry, datasets from 57 patients were selected arbitrarily for comparison of their VCI-C measurements with those from mid-sagittal sections of a stored 3D multiplanar examination. Intraclass correlation was used to evaluate the agreement between these measurements.

RESULTS

The mean maternal age was 32 years. We were able to measure mid-sagittal CC diameter, mid-sagittal AP diameter and cerebellar vermis surface area in all fetuses. Interobserver variability analysis showed no significant differences between the two observers (P > 0.05). Measurements of the cerebellar vermis (AP diameter, CC diameter and surface area) correlated linearly with GA, BPD, HC and TCD (r > or = 0.82, P < 0.0001). CC and AP diameters estimated from the mid-sagittal section of the multiplanar measurements were significantly correlated with VCI-C measurements (r = 0.96, P < 0.00001 and r = 0.95, P < 0.00001, respectively).

CONCLUSIONS

VCI-C is a valuable tool, allowing intrauterine assessment of the normal appearance of the fetal cerebellar vermis. The nomograms developed in this study should enable accurate evaluation of the cerebellar vermis.

Prenatal diagnosis in pregnancies at risk for Joubert syndrome by ultrasound and MRI

OBJECTIVES

To describe the prenatal imaging findings in fetuses at risk for Joubert syndrome (JS), review the literature and propose a protocol for prenatal diagnosis of JS using ultrasound and MRI.

METHODS

We reviewed prenatal ultrasound and fetal MRI studies in two pregnancies at 25% recurrence risk for JS and correlated these findings with gross neuropathology in one affected fetus.

RESULTS

While abnormalities such as occipital encephalocele or enlarged cisterna magna have been identified before mid-trimester, the definitive diagnosis of JS, based on core cerebellar findings, has only been possible after 17 weeks' gestation.

CONCLUSIONS

With longitudinal monitoring, it is possible to diagnose JS in at-risk pregnancies before 24 weeks' gestation. On the basis of our data and review of the literature, we propose a protocol for monitoring pregnancies at risk for JS, utilizing serial ultrasounds combined with fetal MRI at 20-22 weeks' gestation to maximize the accuracy of prenatal diagnosis.

RECOGNITION OF THE CLINICAL SIGNS AND SYMPTOMS OF JOUBERT SYNDROME

Joubert Syndrome is a rare, autosomal recessive disorder that affects the cerebellum and brain stem. It presents with a distinct respiratory pattern and profound tachypnea in the newborn period. This article provides an overview of the condition and discusses the embryologic origins of this syndrome. A focused history and systematic physical assessment provide a step-by-step guide to enhance the early recognition of clinical signs and symptoms of this disorder. A series of clinical photographs and a brief case report offer insight into the classic presentation of this uncommon disorder. The diagnosis of Joubert syndrome is confirmed with magnetic resonance imaging, which reveals a classic neuroradiologic finding, characterized as the molar tooth sign. A discussion of the range of developmental outcomes and complex multispecialty care and intensive support that these infants and their families require is also provided.

Prenatal diagnosis of Joubert syndrome: a case report

Joubert syndrome is a rare, autosomal recessive condition, first described by Joubert in 1969. We present a case of Joubert syndrome from a consanguineous family in which, apart from the cerebellar vermis agenesis, ventriculomegaly, bilateral postaxial polydactyly of hands and right foot and micropenis, episodes of fetal breathing pattern with an increased respiratory rate were also demonstrated by prenatal ultrasound scan. At birth the infant showed an odd face and bilateral fleshy nodules of the tongue. He had an abnormal breathing pattern of alternating tachypnea and apnea. Cranial MRI showed molar tooth sign, hydrocephalus and Dandy-Walker malformation. He had nystagmus, and electroretinography showed retinal dystrophy.