A pathological approach to anomalies of the posterior fossa

Unveiling Dandy-Walker syndrome: A surprising twist in the tale of acute hydrocephalus and Down syndrome child

The correlation between Down syndrome and Dandy-Walker syndrome is an exceptionally uncommon occurrence. To date, only four cases have been documented. All previously reported cases involved individuals under the age of 37 months, with prenatal or birth diagnoses. Additionally, most of these cases displayed a limited life expectancy and experienced poor developmental outcomes. In this report, we present the first-ever instance of an 11-year-old male patient, previously undiagnosed with Dandy-Walker syndrome, who presented with acute intracranial hypertension. Magnetic Resonance Imaging revealed an active hydrocephalus caused by a Dandy-Walker malformation. The patient's condition was effectively managed through the implementation of a ventriculo-cysto-peritoneal shunt. This case highlights the coexistence of Dandy-Walker syndrome and Down syndrome in an asymptomatic young patient. Furthermore, it demonstrates that active hydrocephalus in such cases can be successfully addressed through either endoscopic third ventriculostomy or ventriculo-cysto-peritoneal shunt procedures.

Mega cisterna magna in bipolar mood disorder: a case report

Mega cisterna magna (MCM), one of the members of the Dandy-Walker complex, is a developmental malformation of the posterior fossa that is larger than 10 mm but morphologically does not affect the vermis and cerebellar hemispheres. Reports of psychiatric disorders associated with this anomaly are rare. We present the case of a patient with MCM who presented with a psychotic manic attack and was diagnosed with bipolar disorder. A 28-year-old female, single housewife, university graduate, presented with irritability, decreased sleep and appetite, distraction, and agitation. The patient also had a delusion of reference. In the clinical follow-up, an increase in energy and an increase in the amount of speech were observed. Her neurological examination was normal, and cranial magnetic resonance imaging revealed an MCM. The relationship and clinical significance of MCM with psychosis and mood disorders have not yet been fully elucidated. It is not known whether this association is accidental or based on etiological commonality. The purpose of this case report is to review the relationship between the cerebellum and psychiatric symptoms and to contribute to the literature.

The Role of Fetal MRI for Suspected Anomalies of the Posterior Fossa

BACKGROUND

Posterior fossa anomalies can be diagnostic dilemmas during the fetal period. The prognosis for different diagnoses of the posterior fossa varies widely. We investigated whether fetal magnetic resonance imaging (MRI) and prenatal neurology consultation led to an alternate prognosis for fetuses referred due to concern for a fetal posterior fossa anomaly and concordance between pre- and postnatal diagnoses.

METHODS

This is a retrospective study of cases referred to the Prenatal Pediatrics Institute at Children's National Hospital from January 2012 to June 2018 due to concern for posterior fossa anomaly. Each encounter was scored for change in prognosis based upon clinical and fetal MRI report. Postnatal imaging was compared with prenatal imaging when available.

RESULTS

In total, 180 cases were referred for fetal posterior fossa anomalies based on outside obstetric ultrasound and had both fetal MRI and a neurology consultation. Fetal MRI and neurology consultation resulted in a change in fetal prognosis in 70% of cases. The most common referral diagnosis in our cohort was Dandy-Walker continuum, but it was not often confirmed by fetal MRI. In complex cases, posterior fossa diagnosis and prognosis determined by fetal MRI impacted choices regarding pregnancy management. Postnatal imaging was obtained in 57 (47%) live-born infants. Fetal and postnatal prognoses were similar in 60%.

CONCLUSIONS

Fetal diagnosis affects pregnancy management decisions. The fetal-postnatal imaging agreement of 60% highlights the conundrum of balancing the timing of fetal MRI to provide the most accurate diagnosis of the posterior fossa abnormalities in time to make pregnancy management decisions.

Hindbrain morphometry and choroid plexus position in differential diagnosis of posterior fossa cystic malformations

OBJECTIVE

To assess the differential diagnostic significance of a series of quantitative and qualitative variables of the cerebellar vermis in fetuses with posterior fossa cystic malformation, including Dandy-Walker malformation (DWM), vermian hypoplasia (VH) and Blake's pouch cyst (BPC).

METHODS

This was a retrospective study of confirmed cases of DWM, VH and BPC, diagnosed at the Fetal Medicine and Surgery Unit of the Federico II University between January 2005 and June 2013 or the Fetal Medicine and Surgery Unit of G. Gaslini Hospital between July 2013 and September 2017. All included cases had good-quality three-dimensional (3D) volume datasets of the posterior fossa, acquired by transvaginal ultrasound through the posterior fontanelle. The midsagittal view of the posterior fossa was the reference view for the study. We assessed brainstem-tentorium angle and brainstem-vermis angle (BVA), as well as craniocaudal (CCVD) and anteroposterior (APVD) vermian diameters and vermian area (VA), which were normalized by biparietal diameter (BPD) to take into account gestational age (CCVD/BPD × 100, APVD/BPD × 100 and VA/BPD × 100, respectively). Finally, the position of the fourth ventricular choroid plexus (4VCP) was defined as normal ('up') or abnormal ('down'), relative to the roof/cyst inlet of the fourth ventricle.

RESULTS

We analyzed 67 fetuses with posterior fossa malformations (24 cases of DWM, 13 of VH and 30 of BPC). The mean gestational age at diagnosis was 23.6 weeks. Regardless of gestational age, the BVA differed significantly between the three groups, and the VA/BPD was able to differentiate between VH and BPC. In differentiating between VH and BPC, the greatest areas under the receiver-operating characteristics curve were those for VA/BPD ratio. The 4VCP position was down in all cases of DWM and VH, while it was up in all cases of BPC.

CONCLUSIONS

Our data support the concept that VA/BPD ratio and 4VCP position may be used to differentiate between DWM, VH and BPC in the fetus. In our series, the position of the 4VCP had the highest accuracy, but a larger number of VH cases should be evaluated to confirm that an up position of the 4VCP indicates BPC while a down position indicates DWM or VH. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Perinatal and short-term neonatal outcomes of posterior fossa anomalies

OBJECTIVE

To describe the perinatal and neonatal outcomes for fetuses with posterior fossa (PF) anomalies - mega-cisterna magna (MCM), persistent Blake's pouch (PBP) or the Dandy-Walker continuum (DWC) - using a new classification.

METHODS

46 cases with PF anomaly diagnosed on ultrasound (US) between 16 and 28 weeks' gestation were included. The images were reviewed and classified as one of the following: MCM, PBP or DWC. Outcomes were obtained from patient records.

RESULTS

30 cases with DWC, 6 with MCM, and 10 with PBP were identified. Associated anomalies were present in all groups, but more frequent in DWC. Agenesis of the corpus callosum and ventriculomegaly were more common in DWC than in MCM or PBP. Only fetuses with DWC were found to have chromosomal abnormalities. Perinatal outcomes differed significantly, with terminations of pregnancy more frequent in DWC. In the immediate postnatal period, infants with DWC had worse outcomes than those with MCM and PBP. Across all groups, those with associated anomalies had worse outcomes than those with an isolated PF anomaly.

CONCLUSION

Infants antenatally diagnosed with DWC had worse perinatal and short-term neonatal outcomes than those with MCM or PBP. Those with associated anomalies had uniformly poorer outcomes than those with isolated anomalies.

Endoscopic third ventriculostomy is a safe and effective procedure for the treatment of Blake's pouch cyst

OBJECTIVE: Blake's pouch cyst (BPC) is a midline cystic malformation of the posterior fossa, within Dandy-Walker's complex (DWC), often associated with hydrocephalus. Endoscopic third ventriculostomy (ETV) has been an alternative to conventional methods for BPC treatment. This study aimed at reporting our experience with ETV in a series of patients with BPC. METHODS: Of 33 patients diagnosed with midline posterior fossa cyst, 26 met the protocol criteria for DWC, and eight subjects with BPC were selected (aged one month to two years old). All cases were treated with ETV. RESULTS: Five patients were male; and three were prenatally diagnosed. They had hydrocephalus and motor deficiencies. Motor assessment at a five-year follow-up yielded normal findings. All patients improved, and only one had residual cognitive dysfunction, despite overall neurological improvement. There were no complications. CONCLUSIONS: ETV was a safe and effective procedure, reducing risks and morbidity associated with open surgery and shunt-related problems.

Abnormal or delayed development of the posterior membranous area of the brain: anatomy, ultrasound diagnosis, natural history and outcome of Blake's pouch cyst in the fetus

OBJECTIVES

To review the normal and pathological development of the posterior membranous area (PMA) in the fetal brain, to define sonographic criteria with which to diagnose a Blake's pouch cyst (BPC) in the fetus and to review the ultrasound features, associations and outcome of 19 cases of BPC seen at our center over the last 5 years.

METHODS

We conducted a MEDLINE search using the terms 'Blake's pouch', with or without 'fourth ventricle' or '4(th) ventricle', with or without 'roof' and identified articles describing normal and/or abnormal development of the PMA, whether or not they were cited in the limited clinical literature on BPC. A description of the normal and abnormal development of BPC was derived by collating these articles. The clinical retrospective study included 19 cases of posterior fossa anomalies with a final diagnosis of BPC seen at our institution. The following variables were assessed: referral indication, gestational age at diagnosis, ultrasound and magnetic resonance imaging (MRI) findings, associated anomalies, natural history and pregnancy and neonatal outcome. A transvaginal three-dimensional (3D) ultrasound examination was performed in all cases and 15 cases underwent MRI. To confirm the diagnosis, postnatal MRI, transfontanellar ultrasound or autopsy were available in all cases.

RESULTS

Among the 19 cases reviewed, referral indications were: suspicion of vermian abnormality in 11 (58%) cases and other non-central nervous system anomaly in eight (42%) cases. Sonographically, all cases showed the following three signs: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. On 3D ultrasound, the upper wall of the cyst was clearly visible in 11/19 cases, with choroid plexuses on the superolateral margin of the cyst roof. On follow-up, the BPC had disappeared by 24-26 gestational weeks in six of the 11 cases which did not undergo termination of pregnancy (TOP), and remained unaltered until birth in the other five cases. There were associated anomalies in eight (42%) cases, in five of which this consisted of or included congenital heart disease. Karyotype was available in 14 cases, two of which were abnormal (both trisomy 21). Regarding pregnancy outcome, there were eight (42%) TOPs, two (10%) neonatal deaths and nine (48%) survivors. One neonate, in whom the BPC had disappeared by the time of birth, had obstructive hydrocephaly confirmed. Another neonate was diagnosed with Down syndrome after birth. Excluding the Down syndrome baby, neurodevelopmental outcome was normal at the time of writing in all eight cases.

CONCLUSIONS

Based on our analysis of ultrasound features, we propose that for BPC to be diagnosed in a fetus the following three criteria should be fulfilled: 1) normal anatomy and size of the vermis; 2) mild/moderate anti-clockwise rotation of the vermis; 3) normal size of the cisterna magna. Furthermore, we found that BPC can undergo delayed fenestration at 24-26 weeks in more than 50% of cases. Finally, it seems that BPC shows a risk of association with extracardiac anomalies (heart defects in particular) and, to a lesser extent, trisomy 21.

The clinical spectrum of Blake's pouch cyst: report of six illustrative cases

INTRODUCTION

Although Blake's pouch cyst (BPC) is frequently mentioned in the spectrum of posterior fossa cysts and cystlike malformations since its first description in 1996, its natural history, clinical presentation, specific imaging characteristics, optimal treatment, and outcome are relatively unknown. Consequently, BPC may still be underdiagnosed. We therefore report six cases ranging from a fatal hydrocephalus in a young boy, over an increasing head circumference with or without impaired neurological development in two infants, to a decompensating hydrocephalus at an advanced age.

DISCUSSION

We focus on their radiological uniformity, which should help making the correct diagnosis, and widely variable clinical presentation, which includes adult cases as well. Differentiating BPC from other posterior fossa cysts and cystlike malformations and recognizing the accompanying hydrocephalus are essentially noncommunicating, not only have important implications on clinical management but also on genetic counseling, which is unnecessary in case of BPC. In our experience, endoscopic third ventriculostomy is a safe and effective treatment option, avoiding the risks and added morbidity of open surgery, as well as many shunt-related problems.

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.

A developmental and genetic classification for midbrain-hindbrain malformations

Advances in neuroimaging, developmental biology and molecular genetics have increased the understanding of developmental disorders affecting the midbrain and hindbrain, both as isolated anomalies and as part of larger malformation syndromes. However, the understanding of these malformations and their relationships with other malformations, within the central nervous system and in the rest of the body, remains limited. A new classification system is proposed, based wherever possible, upon embryology and genetics. Proposed categories include: (i) malformations secondary to early anteroposterior and dorsoventral patterning defects, or to misspecification of mid-hindbrain germinal zones; (ii) malformations associated with later generalized developmental disorders that significantly affect the brainstem and cerebellum (and have a pathogenesis that is at least partly understood); (iii) localized brain malformations that significantly affect the brain stem and cerebellum (pathogenesis partly or largely understood, includes local proliferation, cell specification, migration and axonal guidance); and (iv) combined hypoplasia and atrophy of putative prenatal onset degenerative disorders. Pertinent embryology is discussed and the classification is justified. This classification will prove useful for both physicians who diagnose and treat patients with these disorders and for clinical scientists who wish to understand better the perturbations of developmental processes that produce them. Importantly, both the classification and its framework remain flexible enough to be easily modified when new embryologic processes are described or new malformations discovered.

Normal and abnormal anatomy of the cerebellar vermis in midgestational human fetuses

BACKGROUND

Evaluation of the cerebellar vermis is an important component of fetal autopsy, but lack of an established approach, inadequate normal anatomic data, and the subtle nature of some cerebellar malformations negatively affect concordance between prenatal ultrasound and autopsy diagnoses.

METHODS

Gross anatomy and sagittal histologic sections of vermis from 26 midgestation fetuses with no posterior fossa anomalies detected by prenatal ultrasound or autopsy were examined to establish stage-specific norms. These were compared to data from three fetuses with prenatal ultrasound diagnoses of hypoplasia or absence of the cerebellar vermis, each of which had no or equivocal gross cerebellar malformation at autopsy.

RESULTS

Two findings segregated cases from controls: (1) The ratio of the rostro-caudal length of the vermis to that of the cerebellar hemispheres was shorter for cases (<0.7), in comparison with controls (0.7-1). (2) The lobules of the vermis, particularly in the posterior lobe, were less arborized, and the nodulus (caudal-most lobule) was elongated. Prenatal sonograms from the three cases predicted more severe vermis hypoplasia than was evident at autopsy.

CONCLUSIONS

Prenatal ultrasound images that suggest moderate-to-severe hypoplasia of the cerebellar vermis may reflect relatively subtle malformations, which are recognized histologically by direct comparison with stage-matched control data. The data in this series and others suggest a somewhat consistent pattern of lobular malformation, which affects the caudal cerebellum, particularly the nodulus, most severely. Rotation of the cerebellum, secondary to an enlarged fourth ventricle, may account for discordance between ultrasound and autopsy findings.

How accurately does current fetal imaging identify posterior fossa anomalies?

OBJECTIVE

The first objective of our study was to describe the prevalence and spectrum of posterior fossa anomalies over 5 years in a major fetal care center where the referral diagnosis (by fetal sonography) was investigated by fetal MRI and, if confirmed, by postnatal MRI if possible. The second objective was to assess the accuracy with which fetal MRI predicts postnatal MRI findings in this population.

MATERIALS AND METHODS

We retrospectively identified all cases of suspected fetal posterior fossa anomalies referred to our center from 2002 through 2006. We reviewed maternal, fetal, neonatal, and follow-up records of all cases and fetal and early postnatal imaging studies.

RESULTS

Of the 90 cases of suspected fetal posterior fossa anomalies (by fetal sonography) referred over the study period, 60 (67%) were confirmed by fetal MRI. Of 42 live-born infants, 39 (93%) underwent postnatal MRI. There was complete agreement in fetal and postnatal MRI diagnoses in 23 infants (59%). In 16 cases (41%), fetal and postnatal MRI diagnoses disagreed; postnatal MRI excluded fetal MRI diagnoses in six cases (15%) and revealed additional anomalies in 10 cases (26%).

CONCLUSION

Although a valuable adjunct to fetal sonography in cases of suspected posterior fossa anomaly, current fetal MRI, particularly in early gestation, has limitations in accurately predicting postnatal MRI abnormalities. Advancing the accuracy of MRI for the diagnosis of posterior fossa anomalies will require greater understanding of normal brain development and improved tissue resolution of fetal MRI. During the interim, our findings strongly support the need for postnatal MRI follow-up in cases with suspected posterior fossa anomalies by fetal MRI.

The Fetal Posterior Fossa

OBJECTIVES

Recognize posterior fossa anomalies on ultrasound and magnetic resonance imaging and appreciate imaging pitfalls that may lead to misdiagnosis.

MATERIALS AND METHODS

Cases are presented to illustrate normal development and various anomalies. Postnatal studies and autopsy are used for correlation with prenatal imaging.

RESULTS

Normal anatomy and anomalies are demonstrated. Pitfalls such as cystic hygroma, pseudomasses, and use of nonstandard scan planes are illustrated.

CONCLUSIONS

Recognizing normal developing structures is an important component of performing fetal ultrasound. Documentation of the cerebellum, vermis, and cisterna magna are required for posterior fossa evaluation in any American Institute of Ultrasound in Medicine-certified practice. Normal variations are common, and understanding the anatomy is vital to avoid misdiagnosis and to accurately characterize abnormalities.