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

Not Dandy Walker variant: a review of prominent retrocerebellar CSF space in children

The prominent retrocerebellar cerebrospinal fluid (CSF) space can be frequently encountered on paediatric neuroimaging studies. In cases involving abnormal vermian development where imaging does not align with the established criteria of Dandy-Walker malformation (DWM), the term "Dandy-Walker variant or continuum" has been historically employed to describe the aberrant posterior fossa development. Instead, the emphasis is on a more elaborate description of the findings in the posterior fossa. Moreover, combining the findings in the supratentorial brain can occasionally predict certain neurogenetic disorders that mimic Dandy-Walker phenotype. The present review demonstrates and differentiates the imaging features of various entities that result in an enlarged retrocerebellar CSF space, such as inferior vermian hypoplasia (IVH) and several neurogenetic conditions.

The Management of Hydrocephalus in Midline Posterior Fossa Cystic Collections: Surgical Outcome From a Retrospective Single-Center Case Series of 54 Consecutive Pediatric Patients

BACKGROUND

Hydrocephalus frequently occurs with midline posterior fossa cystic collections. The classification of this heterogeneous group of developmental anomalies, including Dandy-Walker malformation, persisting Blake's pouch, retrocerebellar arachnoid cysts, and mega cisterna magna, is subject of debate. The absence of diagnostic criteria is confusing regarding the ideal management of PFCC-related hydrocephalus.

OBJECTIVE

To decipher the surgical strategy for the treatment of children with PFCC-related hydrocephalus through a retrospective analysis of the surgical outcome driven by their clinical and radiological presentation.

METHODS

This study enrolled patients operated of symptomatic PFCC-related hydrocephalus. Clinical and MRI features were examined, as well as the surgical outcome. Unbiased subgroup classification of the patients was performed with multiple component analysis as a function of imaging characteristics and hierarchical clustering on principal component. Outcome was assessed with binomial logistic regression and Kaplan-Meier analysis.

RESULTS

Fifty-four patients were included between 2007 and 2021. Multiple component analysis suggested that cerebellar and vermian hypoplasia, vermian rotation, basal-tentorial angle, and fastigial angle were strongly correlated. Hierarchical clustering and the distribution of the patients in the bidimensional plot showed the clear segregation of 3 major clusters, which correlated with the radiological diagnosis ( P < .01). Binomial logistic regression and survival analysis showed that endoscopic third ventriculostomy was an effective treatment for patients with persisting Blake's pouch, while failing to control hydrocephalus in most of patients with Dandy-Walker malformation.

CONCLUSION

Preoperative MRI in patients with PFCC-related hydrocephalus is essential to better define the diagnosis. The choice of treatment strategy notably relies on correct radiological diagnosis.

Imaging of congenital and developmental cystic lesions of the brain: a narrative review

INTRODUCTION

Congenital and developmental intracranial cysts represent a large heterogenous group with varied presentations and etiologies. They can range from normal variants to pathologic lesions often associated with known congenital syndromes or acquired insults. While some are incidentally found, others are symptomatic or may become symptomatic over time. The preferred type of neuroimaging for timely diagnosis helps determine appropriate management and treatment, if indicated.

AREAS COVERED

In this narrative review article, authors present a comprehensive description of developmental cystic lesions. Imaging descriptions are provided for each type of cystic lesion as well as several representative images.

EXPERT OPINION

As advanced neuroimaging techniques become more ubiquitous in clinical use, more light may be shed on the natural history of certain intracranial cystic lesions throughout the lifespan. This includes prenatal imaging for early identification and prognostication to surveillance imaging into advanced age to ascertain associations of certain cystic lesions with age-related cognitive dysfunction.

Atavistic and vestigial anatomical structures in the head, neck, and spine: an overview

Organisms may retain nonfunctional anatomical features as a consequence of evolutionary natural selection. Resultant atavistic and vestigial anatomical structures have long been a source of perplexity. Atavism is when an ancestral trait reappears after loss through an evolutionary change in previous generations, whereas vestigial structures are remnants that are largely or entirely functionless relative to their original roles. While physicians are cognizant of their existence, atavistic and vestigial structures are rarely emphasized in anatomical curricula and can, therefore, be puzzling when discovered incidentally. In addition, the literature is replete with examples of the terms atavistic and vestigial being used interchangeably without careful distinction between them. We provide an overview of important atavistic and vestigial structures in the head, neck, and spine that can serve as a reference for anatomists and clinical neuroscientists. We review the literature on atavistic and vestigial anatomical structures of the head, neck, and spine that may be encountered in clinical practice. We define atavistic and vestigial structures and employ these definitions consistently when classifying anatomical structures. Pertinent anatomical structures are numerous and include human tails, plica semilunaris, the vomeronasal organ, levator claviculae, and external ear muscles, to name a few. Atavistic and vestigial structures are found throughout the head, neck, and spine. Some, such as human tails and branchial cysts may be clinically symptomatic. Literature reports indicate that their prevalence varies across populations. Knowledge of atavistic and vestigial anatomical structures can inform diagnoses, prevent misrecognition of variation for pathology, and guide clinical interventions.

Endoscopic third ventriculostomy for patients with Blake's pouch cyst with adult-onset hydrocephalus: Importance of improved cerebrospinal fluid flow in the prepontine cistern - A case report

Background

Blake's pouch cyst (BPC) is a posterior fossa cystic malformation that commonly occurs in children with rare adult onset. Herein, we report a case of adult onsets BPC.

Case Description

A 61-year-old man presented with gait and cognitive disturbance. Preoperative magnetic resonance imaging (MRI) revealed scarring in the prepontine cistern, and cine phase-contrast MRI revealed no pulsation. Endoscopic third ventriculostomy (ETV) was performed with opening the scarring in the prepontine cistern. Postoperative cine phase-contrast MRI revealed that cerebrospinal fluid (CSF) flow in the prepontine cistern improved, resolving the patient's symptoms.

Conclusion

We report a case of adult-onset BPC. The mechanism by which is becomes symptomatic is still unclear. We opened the scar in prepontine cistern in addition to ETV with good results. In this report, we discussed the importance of the improvement in CSF dynamics in the prepontine cistern.

Challenges in the pre- and post-natal diagnosis of posterior fossa cysts: A case report and review of historical evolution of descriptive terminologies

Background:

Radiological diagnoses of posterior fossa cystic abnormalities during antenatal and postnatal periods pose significant challenges as they may have similar early imaging features. Some of the frequently described entities are arachnoid cysts and Dandy-Walker malformations. Blake’s pouch cyst is relatively underdiagnosed. The main aim of the study was to explore these diagnostic challenges in the context of various descriptive terminologies and their prognostic implications.

Methods:

We illustrate this through our case, where fetal magnetic resonance imaging (MRI) at 36 weeks gestation showed small right cerebellum without hydrocephalus or hemorrhage. Possible differential diagnoses included Dandy-Walker malformation or posterior fossa malformations, facial hemangiomas, arterial anomalies, cardiac and eye anomalies, sternal clefting, and supraumbilical raphe.

Results:

Postnatal sonography noted posterior fossa cyst without hydrocephalus in a normal term infant, who went on to develop symptomatic hydrocephalus by 15 weeks. Computed tomography brain scan confirmed large subtentorial posterior fossa cyst and extensive internal hydrocephalus. Despite emergent ventriculoperitoneal shunt insertion, head circumference continued to rise. MRI scan showed persistent cyst. Subsequently, infant underwent endoscopic fenestration of the cyst with balloon septostomy and now has an age appropriate developmental profile.

Conclusion:

There is considerable discordance between antenatal and postnatal neuroimaging findings as highlighted in our case. Diagnostic conundrum here was whether this was an arachnoid or Blake’s pouch cyst. Differentiating between posterior fossa fluid collections is crucial for management, prognosis, and parental counseling. Close postnatal follow-up is essential to avert complications due to acute hydrocephalus.

Tetraventricular noncommunicating hydrocephalus: Case report and literature review

BACKGROUND

Tetraventricular hydrocephalus is a common presentation of communicating hydrocephalus. Conversely, cases with noncommunicating etiology impose a diagnostic challenge and are often neglected and underdiagnosed. Herein, we present a review of literature for clinical, diagnostic, and surgical aspects regarding noncommunicating tetrahydrocephalus caused by primary fourth ventricle outlet obstruction (FVOO), illustrating with a case from our service.

METHODS

We performed a research on PubMed database crossing the terms "FVOO," "tetraventriculomegaly," and "hydrocephalus" in English. Fifteen articles (a total of 34 cases of primary FVOO) matched our criteria and were, therefore, included in this study besides our own case.

RESULTS

Most cases presented in adulthood (47%), equally divided between male and female. Clinical presentation was unspecific, commonly including headache, nausea, and dizziness as symptoms (35.29%, 21.57%, and 9.80%, respectively), with ataxic gait (65%) and papilledema (40%) being the most frequent signs. MRI and CT were the imaging modalities of choice (11 patients each), often associated with CSF flow studies, such as cine MRI and CT ventriculogram. Endoscopic third ventriculostomy (ETV) was both the most popular and effective surgical approach (50.85% of cases, with 18.91% of recurrence) followed by ventricle-peritoneal shunt (16.95% of patients, 23.0% of recurrence).

CONCLUSION

FVOO stands for a poorly understood etiology of noncommunicating tetrahydrocephalus. With the use of ETV, these cases, once hopeless, had its morbimortality and recurrence reduced greatly. Therefore, its suspicion and differentiation from other forms of tetrahydrocephalus can improve its natural course, reinforcing the importance of its acknowledgment.

Short- and Long-Term Outcomes of Prenatally Diagnosed Dandy-Walker Malformation, Vermian Hypoplasia, and Blake Pouch Cyst

Dandy-Walker continuum, which includes Dandy-Walker malformation, vermian hypoplasia, and Blake pouch cyst, is among the most commonly diagnosed posterior fossa malformation by fetal magnetic resonance imaging (MRI). The objective of our retrospective study was to evaluate fetal and postnatal MRI scan and clinical outcomes. Seventy-two patients were identified; 40 patients had postnatal imaging and follow-up (7 Dandy-Walker malformation, 26 vermian hypoplasia, and 7 Blake pouch cyst). Although all patients with Dandy-Walker malformation required ventriculoperitoneal shunts and 66% were intubated at birth, none required tracheostomy tube and 2 of 5 surviving children had no neurologic deficits. Vermian hypoplasia was strongly associated with genetic conditions and cardiac malformations; odds of not ambulating normally were 12 times greater if a syndrome or injury was present. Echocardiogram and genetic screening are recommended with vermian hypoplasia. There is a risk for epilepsy in both Dandy-Walker malformation and vermian hypoplasia. Blake pouch cyst can be complicated by hydrocephalus, but outcome is favorable.

Evaluation of Posterior Fossa Biometric Measurements on Fetal MRI in the Evaluation of Dandy-Walker Continuum

BACKGROUND AND PURPOSE

Dandy-Walker malformation, vermian hypoplasia, and Blake pouch remnant represent a continuum of anomalies and are common reasons for referral for fetal MR imaging. This study aimed to determine biometric measurements that quantitatively delineate these 3 posterior fossa phenotypes.

MATERIALS AND METHODS

Our single-center institutional review board approved a retrospective analysis of all fetal MRIs for posterior fossa malformations, including Dandy-Walker malformation, vermian hypoplasia, and Blake pouch remnant. Measurements included the anterior-to-posterior pons, craniocaudal and anterior-to-posterior vermis, lateral ventricle size, and tegmentovermian and posterior fossa angles. Measurements were compared with normal biometry and also between each subgroup.

RESULTS

Thirty-three fetuses met the criteria and were included in the study. Seven were designated as having Dandy-Walker malformation; 16, vermian hypoplasia; and 10, Blake pouch remnant. No significant group interactions with adjusted mean gestational age for tegmentovermian and posterior fossa angles were observed. The tegmentovermian angle was significantly higher in Dandy-Walker malformation (109.5° [SD, 20.2°]) compared with vermian hypoplasia (52.13° [SD, 18.8°]) and Blake pouch remnant (32.1° [SD, 17.9°]), regardless of gestational age. Lateral ventricle sizes were significantly higher in Dandy-Walker malformation at a mean of ≥23.1 weeks' gestational age compared with vermian hypoplasia and Blake pouch remnant. The anterior-to-posterior and craniocaudal vermes were significantly smaller in Dandy-Walker malformation compared with vermian hypoplasia and Blake pouch remnant at mean of ≥23.1 weeks' gestational age.

CONCLUSIONS

Dandy-Walker malformation can be described in relation to vermian hypoplasia and Blake pouch remnant by an increased tegmentovermian angle; however, other potential qualifying biometric measurements are more helpful at ≥23.1 weeks' gestational age. Because they fall along the same spectrum of abnormalities, the difficulty in distinguishing these entities from one another makes precise morphologic and biometric descriptions important.

Blake's pouch cyst: Prenatal diagnosis and management

Objective:

This study aimed to present the characteristic features of 19 patients who were diagnosed as having Blake’s pouch cyst (BPC) at our center.

Materials and Methods:

Nineteen patients diagnosed as BPC between 2015 and 2019 were included in this retrospective study. Follow-up examinations were performed using ultrasonography (US) every three weeks up to 35 weeks of gestation. Prenatal magnetic resonance imaging (MRI) was performed at the time of diagnosis or during follow-up in 13 patients. MRI or transfontanellar US was performed to confirm the diagnosis of BPC after delivery. Karyotype results of eight patients were recorded.

Results:

Isolated BPC was observed in 9 (47%) patients, and associated anomalies were detected in 10 (53%) patients, including seven (36%) with the central nervous system and four (21%) with cardiac anomalies. Two fetuses had abnormal karyotype analysis as trisomy 21 and 13. The MRI report of eight patients was “differential diagnosis required for Dandy-Walker complex” and only in five (26%) patients, it was reported to be compatible with BPC. Spontaneous resolution was seen in four patients. Postnatal MRI was performed in five patients, and transfontanellar US in two patients, and all MRI and US results were consistent with BPC. During the neonatal period, abnormal neurologic development was observed in four (21%) patients, and one (5%) died.

Conclusion:

Although the prognosis of isolated BPC is very good with healthy neurologic development until advanced ages, death in the early neonatal period and abnormal neurologic development may be observed depending on the condition of the associated anomalies.

Guidelines for Management of Idiopathic Normal Pressure Hydrocephalus (Third Edition): Endorsed by the Japanese Society of Normal Pressure Hydrocephalus

Among the various disorders that manifest with gait disturbance, cognitive impairment, and urinary incontinence in the elderly population, idiopathic normal pressure hydrocephalus (iNPH) is becoming of great importance. The first edition of these guidelines for management of iNPH was published in 2004, and the second edition in 2012, to provide a series of timely, evidence-based recommendations related to iNPH. Since the last edition, clinical awareness of iNPH has risen dramatically, and clinical and basic research efforts on iNPH have increased significantly. This third edition of the guidelines was made to share these ideas with the international community and to promote international research on iNPH. The revision of the guidelines was undertaken by a multidisciplinary expert working group of the Japanese Society of Normal Pressure Hydrocephalus in conjunction with the Japanese Ministry of Health, Labour and Welfare research project. This revision proposes a new classification for NPH. The category of iNPH is clearly distinguished from NPH with congenital/developmental and acquired etiologies. Additionally, the essential role of disproportionately enlarged subarachnoid-space hydrocephalus (DESH) in the imaging diagnosis and decision for further management of iNPH is discussed in this edition. We created an algorithm for diagnosis and decision for shunt management. Diagnosis by biomarkers that distinguish prognosis has been also initiated. Therefore, diagnosis and treatment of iNPH have entered a new phase. We hope that this third edition of the guidelines will help patients, their families, and healthcare professionals involved in treating iNPH.

Fetal and postnatal MRI findings of Blake pouch remnant causing obstructive hydrocephalus

Blake pouch remnant, also known as Blake pouch cyst or persistent Blake pouch, is a posterior fossa embryologic anomaly that is often seen in isolation with most affected patients being asymptomatic. However, even in isolation, Blake pouch remnant can result in obstructive hydrocephalus requiring early neurosurgical intervention making it an important diagnosis for the fetal radiologist to consider. We present a rare case of a patient with prenatally diagnosed "inferior vermian hypoplasia" on fetal MRI that went on to develop progressive obstructive hydrocephalus in infancy secondary to what was determined to be a Blake pouch remnant.

Progressive Hydrocephalus after Endoscopic Third Ventriculostomy in Pediatric Patients with Blake's Pouch Cyst

The pathophysiology and optimal treatment for hydrocephalus with Blake’s pouch cyst (BPC) remain controversial. The authors present two pediatric cases of hydrocephalus associated with BPC, in which the patients’ hydrocephalus progressed after endoscopic third ventriculostomy (ETV), despite a patent stoma of the third ventricular floor.

Case 1: A 4-year-old girl with delayed gait development was diagnosed with BPC-associated hydrocephalus and received ETV. Postoperatively, the patient presented headaches and nausea. Computed tomography (CT) scans demonstrated larger ventricles than those observed on the preoperative images. Because phase-contrast cine magnetic resonance imaging (MRI) and constructive interference in steady state (CISS) MRI revealed patent cerebrospinal fluid (CSF) flow at the third ventricular floor level, a ventriculoperitoneal shunt (VPS) was placed using a programmable pressure valve to treat the hydrocephalus.

Case 2: A 6-year-old girl with newly developed repeated convulsive seizures was diagnosed with BPC-associated hydrocephalus and received ETV. Phase-contrast cine MRI on the 5th postoperative day showed hyperdynamic CSF flow at the third ventricular floor level. She also developed vomiting and headache 6 weeks after ETV. CT scans demonstrated much larger tetraventricular hydrocephalus than that observed on the preoperative images. VPS placement improved her hydrocephalus.

Referencing the previous literature, we discuss the CSF dynamics and the mechanism of BPC-associated hydrocephalus, focusing on the third ventricular floor bulging. We hope our experience will help elucidate the pathophysiology and treatment strategies for BPC-associated hydrocephalus.

Blake's Pouch Cysts and Differential Diagnoses in Prenatal and Postnatal MRI : A Pictorial Review

PURPOSE

The clinical variability of Blake's pouch cysts (BPC) may range from asymptomatic via ataxia to sequelae of decompensated hydrocephalus. On the other hand, Dandy-Walker malformation (DWM) and cerebellar vermis hypoplasia generally correlate with less favorable neurologic development. The aim was to illustrate the potential of prenatal and postnatal neuroimaging to distinguish a BPC or persistent BP from other posterior fossa malformations.

METHODS

This pictorial review addresses the inconsistent nomenclature, clinical features, and magnetic resonance imaging (MRI) patterns of BPC and five differential diagnoses. The MRI findings of 11 patients, acquired at up to 3 T in 3 institutions, are demonstrated. Furthermore, the literature was searched for recent improvements in genetic and embryological background knowledge.

RESULTS

Posterior fossa malformations often resemble each other and may even be imitated by sequelae of hemorrhagic, ischemic or infectious disruptions, i.e. congenital anomalies of morphology despite normal developmental potential. Hydrocephalus is a typical, albeit not always congenital finding in BPC. It is frequently associated with cerebellar disruptions and DWM; however, it is also a rare complication of posterior fossa arachnoid cysts. A moderately elevated vermis needs follow-up to confirm persistent BP versus vermian hypoplasia or DWM. The fetal cerebellar tail, previously assumed to be specific for DWM, may be imitated in cases of persistent BP.

CONCLUSION

The accurate diagnosis of isolated BPC is not always straightforward, which is especially critical in the context of fetomaternal medicine. A detailed description of posterior fossa malformations is to be preferred over unspecific terminology.

Prenatal magnetic resonance imaging within the 26th week of gestation may predict the fate of isolated upward rotation of the cerebellar vermis: insights from a multicentre study

OBJECTIVES

We investigated whether prenatal magnetic resonance imaging (MRI) within 26 weeks of gestation (GW) may predict the fate of isolated upward rotation of the cerebellar vermis (URCV).

METHODS

This retrospective multicentre observational study included foetuses diagnosed with isolated URCV in prenatal MRI performed within 26 GW. Isolated URCV was defined by a brainstem-vermis angle (BVA) ≥ 12° in the MR midline sagittal view without abnormalities of the supratentorial structures, brainstem, or cerebellum hemispheres. The assessments included the BVA, clival-supraoccipital angle, transverse diameter of the posterior cranial fossa, tentorial angle, width of the cisterna magna (WCM), ventricular width, vermian diameters, hypointense stripes, and cerebellar tail sign. Late prenatal or postnatal MRI was used as a reference standard to assess the final vermian fate (rotated/de-rotated).

RESULTS

Forty-five foetuses (mean GW at prenatal MRI = 21.5 ± 1.4 weeks) were included. In the reference standard, the vermis was de-rotated in 26 cases (57.7%). At least two of the following criteria were used to predict the persistence of URCV at imaging follow-up: BVA ≥ 23°, WCM ≥ 9 mm, and the cerebellar tail sign. The results were a sensitivity of 84.21% (95% CI, 60.4-96.6%), specificity of 80.8% (95% CI, 60.6-93.4%), positive predictive value of 76% (95% CI, 58.7-87.8%), and negative predictive value of 87.5% (95% CI, 70.9-95.2%).

CONCLUSIONS

MRI within 26 GW on foetuses diagnosed with isolated URCV may predict delayed cerebellar vermis de-rotation, which is associated with good neurodevelopmental outcome in most cases.

KEY POINTS

• Foetal MRI is a valuable tool in predicting the fate of isolated upward-rotated cerebellar vermis. • A wider angle between the brainstem and vermis is associated with higher risk of persistence of vermian rotation. • The presence of ≥ 2 factors among a brainstem-to-vermis angle ≥ 23°, width of the cisterna magna ≥ 9 mm, and the presence of the "cerebellar tail sign" has a sensitivity of 84.21% (95% CI, 60.4-96.6%) and specificity of 80.8% (95% CI, 60.6-93.4%) in predicting the persistence of the vermian rotation at imaging follow-up.

Developmental Retrocerebellar Cysts: A New Classification for Neuroendoscopic Management and Systematic Review

OBJECTIVE

Posterior fossa cystic malformations are diversely classified with considerable overlap without therapeutic relevance. These cysts posterior to the cerebellum, presenting in children younger than 5 years, are labeled developmental retrocerebellar cysts (DRCCs) under a new classification in relation to neuroendoscopy.

METHODS

DRCC was categorized as type 0 for asymptomatic enlarged cistern magna and was not treated. Among symptomatic cases, cysts with a compressed fourth ventricle were labeled type 1, whereas cysts in continuity with the fourth ventricle were termed type 2. They were further categorized as subtype B if hydrocephalus was greater relative to the cyst, or otherwise as subtype A. The literature was reviewed according to PRISMA guidelines.

RESULTS

There were 13 children aged 3-48 months. Type 1A DRCC was noted in 5 patients, with onset before 6 months, 4 of whom (80%) had intracranial hypertension. All underwent suboccipital endoscopic deroofing and cisternostomy (SEDC), a new technique. Type 1B DRCC was seen in 2 patients, with onset at 8-9 months, who underwent endoscopic third ventriculostomy (ETV) + endoscopic ventriculocystostomy (EVC). Type 2A DRCC was observed in 4 patients, with onset at 5-47 months, who underwent SEDC. Type 2B DRCC was noted in 2 patients, with onset 6-8 months, who underwent ETV. With a mean follow-up of 32 months, all showed clinicoradiologic improvement. The application of our classification to other studies showed ETV/EVC to be successful in only 67% of type 1A DRCC and 72% of type 2A DRCC, compared with 100% efficacy of SEDC in our series.

CONCLUSIONS

This is probably the first ever endoscopic classification of pediatric posterior fossa cyts, elucidating pathophysiology, presentation, and treatment. Patients with type 1 DRCC present early because of extraneous compression. Among patients with type 2 DRCC, posterior fossa compliance determines the degree of hydrocephalus. The newly described SEDC seems more appropriate for types 1A and 2A DRCC. ETV is adequate in type 2B DRCC and effective with EVC in type 1B.

Post Mortem Diagnosis of Blake's Pouch Cyst: A Presentation of Distended Cyst at Necropsy

BACKGROUND

Blake's pouch cyst forms from non-permeabilization of Blake's pouch. It is difficult to visualize at necropsy as the cyst ruptures easily into the 4th ventricle during dissection.

CASE REPORT

Based upon prenatal imaging, delicate dissection allowed post-mortem confirmation of the Blake's pouch cyst.

CONCLUSIONS

This highlights the importance of utilizing premortem imaging to help guide the postmortem dissection and documentation of a posterior fossa cyst.

Blake's pouch cyst in children: Atypical clinical presentation

Blake's pouch cyst is a posterior fossa cystic malformation characterized by a infracerebellar cyst, absence of communication between the fourth ventricle and the subarachnoid space, and tetraventricular hydrocephalus. Children with Blake's pouch cyst typically present with macrocephaly due to hydrocephalus during the neonatal period or infancy. Atypical presentation is, however, possible. Here we present clinical and neuroimaging findings, as well as management and outcome, of an 18-month-old girl with atypical presentation of Blake's pouch cyst characterized by cerebellar ataxia. Familiarity with the neuroimaging findings of Blake's pouch cyst and differentiation between Blake's pouch cyst and other posterior fossa cystic malformations is important in terms of diagnosis, management, prognosis, and counseling of the affected families.

Panventriculomegaly with a wide foramen of Magendie and large cisterna magna

OBJECT The authors' goal in this paper is to provide the first clinical, radiological, and genetic studies of panventriculomegaly (PaVM) defined by a wide foramen of Magendie and large cisterna magna. METHODS Clinical and brain imaging data from 28 PaVM patients (including 10 patients from 5 families) were retrospectively studied. Five children were included. In adult patients, the age at onset was 56.0 ± 16.7 years. Tetraventricular dilation, aqueductal opening with flow void on T2-weighted images, and a wide foramen of Magendie and large cisterna magna (wide cerebrospinal fluid space at the fourth ventricle outlet) were essential MRI findings for PaVM diagnosis. 3D fast asymmetrical spin echo sequences were used for visualization of cistern membranes. Time-spatial labeling inversion pulse examination was performed to analyze cerebrospinal fluid movement. Copy number variations were determined using high-resolution microarray and were validated by quantitative polymerase chain reaction with breakpoint sequencing. RESULTS Adult patients showed gait disturbance, urinary dysfunction, and cognitive dysfunction. Five infant patients exhibited macrocranium. Patients were divided into 2 subcategories, those with or without downward bulging third ventricular floors and membranous structures in the prepontine cistern. Patients with bulging floors were successfully treated with endoscopic third ventriculostomy. Genetic analysis revealed a deletion in DNAH14 that encodes a dynein heavy chain protein associated with motile cilia function, and which co-segregated with patients in a family without a downward bulging third ventricular floor. CONCLUSIONS Panventriculomegaly with a wide foramen of Magendie and a large cisterna magna may belong to a subtype of congenital hydrocephalus with familial accumulation, younger age at onset, and symptoms of normal pressure hydrocephalus. In addition, a family with PaVM has a gene mutation associated with dysfunction of motile cilia.

Spontaneous resolution of Blake's pouch cyst

Blake's pouch cyst is a rare posterior fossa cystic lesion characterized by posterior ballooning of the superior medullary velum into the cisterna magna. It must be differentiated from severe malformations like inferior vermian hypoplasia and Dandy Walker malformation. We describe a case in which a diagnosis of Blake's pouch cyst was made on prenatal ultrasound and later confirmed by MRI. The cyst showed complete regression on postnatal MRI.

Congenital basis of posterior fossa anomalies

The classification of posterior fossa congenital anomalies has been a controversial topic. Advances in genetics and imaging have allowed a better understanding of the embryologic development of these abnormalities. A new classification schema correlates the embryologic, morphologic, and genetic bases of these anomalies in order to better distinguish and describe them. Although they provide a better understanding of the clinical aspects and genetics of these disorders, it is crucial for the radiologist to be able to diagnose the congenital posterior fossa anomalies based on their morphology, since neuroimaging is usually the initial step when these disorders are suspected. We divide the most common posterior fossa congenital anomalies into two groups: 1) hindbrain malformations, including diseases with cerebellar or vermian agenesis, aplasia or hypoplasia and cystic posterior fossa anomalies; and 2) cranial vault malformations. In addition, we will review the embryologic development of the posterior fossa and, from the perspective of embryonic development, will describe the imaging appearance of congenital posterior fossa anomalies. Knowledge of the developmental bases of these malformations facilitates detection of the morphological changes identified on imaging, allowing accurate differentiation and diagnosis of congenital posterior fossa anomalies.

Symptomatic foramen of Magendie arachnoid cyst in an elderly patient

Background:

Arachnoid cysts (ACs) are congenital anomalies of the central nervous system and arise in virtually all locations where the arachnoid membrane exists. Posterior fossa ACs are considered to develop in the posterior aspect of the rhombencephalic roof plate and do not communicate freely with the fourth ventricle or perimedullary subarachnoid space. Although posterior fossa ACs have been reported a number of times, ACs arising from the foramen of Magendie are very rare.

Case Description:

We report here on a 76-year-old female who presented with progressive gait disturbance. Magnetic resonance imaging of the head showed a large AC in the foramen of Magendie that was compressing the inferior vermis and medial aspects of the cerebellar hemisphere without causing hydrocephalus. Neurological examination revealed cerebellar ataxia without Romberg's sign. A nearly total excision of the cyst was safely performed via a median suboccipital approach. The patient's postoperative course was excellent and her neurological recovery was remarkable.

Conclusion:

Most cases of ACs located in the foramen of Magendie are reported in children, and it is extremely rare to observe such ACs in the elderly. In fact, to our knowledge, a symptomatic foramen Magendie AC has never been reported previously in an elderly person. Our results indicate that proper surgical intervention can yield highly positive outcomes in such cases.

Postnatal development of Blake's pouch cyst: a case report and new insight for its pathogenesis

Blake's pouch cyst (BPC), a rare cystic malformation in the posterior fossa, is believed to be caused by the congenital expansion of the posterior membranous area that normally regresses during embryogenesis. However, due to the wide spectrum of the onset pattern and age of patients, the natural history and the pathogenesis are poorly understood. The authors describe the case of a girl who admitted with headache and right abducens nerve paresis at the age of 3 years and 10 months. Magnetic resonance (MR) imaging demonstrated a tetraventricular hydrocephalus, an open aqueduct, and a posterior fossa cyst compatible with BPC. Multiple tumors were also noticed in the ventricular wall. Tumor biopsy and an endoscopic third ventriculostomy were performed. Intraoperative observation confirmed the BPC, and pathological diagnosis was pilomyxoid astrocytoma. In retrospect, MR imaging was performed twice in the past, at the age of 8 months and again at 22 months, and no anomaly was detected, suggesting that Blake's pouch was once regressed. Therefore, a BPC in this patient was certainly developed after her second or third year of life. The ventricular tumors may influence the cerebrospinal fluid (CSF) absorption, which triggered the re-expansion of BPC from the possible remnant of Blake's pouch. This is a rare but important report providing evidence that in addition to the classic congenital BPC in which the remnant of Blake's pouch remains persistent, there could be postnatal or secondary BPC, which develops after birth. Possible mechanisms include that the remnant of Blake's pouch, which originally disappears, may re-expand postnatally in association with unknown trigger or a change in CSF dynamics or absorption.

Blake's pouch cyst and Werdnig-Hoffmann disease: Report of a new association and review of the literature

Background:

We report a case of a neonate with proximal spinal muscular atrophy (SMA) type 1 (also known as Werdnig-Hoffmann disease or severe infantile acute SMA) associated with a Blake's pouch cyst; a malformation that is currently classified within the spectrum of Dandy-Walker complex. The association of the two conditions has not been previously reported in the English literature. A comprehensive review of the pertinent literature is presented.

Case Description:

A male neonate was noted to have paucity of movement of the four limbs with difficulty of breathing and poor feeding soon after birth. Respiratory distress with tachypnea, necessitated endotracheal intubation and mechanical ventilation. Pregnancy was uneventful except for decreased fetal movements reported by the mother during the third trimester. Neurological examination revealed generalized hypotonia with decreased muscle power of all limbs, nonelicitable deep tendon jerks, and occasional tongue fasciculations. Molecular genetic evaluation revealed a homozygous deletion of both exons 7 and 8 of the survival motor neuron 1 (SMN1) gene, and exon 5 of the neuronal apoptosis inhibitory protein (NAIP) gene on the long arm of chromosome 5 consistent with Werdnig-Hoffmann disease (SMA type 1). At the age of 5 months, a full anterior fontanelle and abnormal increase of the occipito-frontal circumference were noted. Computed tomographic (CT) scan and magnetic resonance imaging (MRI) of the brain revealed a tetraventricular hydrocephalus and features of Blake's pouch cyst of the fourth ventricle.

Conclusions:

This case represents a previously unreported association of Blake's pouch cyst and SMA type 1.

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.

Prenatal diagnosis and outcome of fetal posterior fossa fluid collections

OBJECTIVE

To evaluate the accuracy of fetal imaging in differentiating between diagnoses involving posterior fossa fluid collections and to investigate the postnatal outcome of affected infants.

METHODS

This was a retrospective study of fetuses with posterior fossa fluid collections, carried out between 2001 and 2010 in two referral centers for prenatal diagnosis. All fetuses underwent multiplanar neurosonography. Parents were also offered fetal magnetic resonance imaging (MRI) and karyotyping. Prenatal diagnosis was compared with autopsy or postnatal MRI findings and detailed follow-up was attempted by consultation of medical records and interview with parents and pediatricians.

RESULTS

During the study period, 105 fetuses were examined, at a mean gestational age of 24 (range, 17-28) weeks. Sonographic diagnoses (Blake's pouch cyst, n = 32; megacisterna magna, n = 27; Dandy-Walker malformation, n = 26; vermian hypoplasia, n = 17; cerebellar hypoplasia, n = 2; arachnoid cyst, n = 1) were accurate in 88% of the 65 cases in which confirmation was possible. MRI proved more informative than ultrasound in only 1/51 cases. Anatomic anomalies and/or chromosomal aberrations were found in 43% of cases. Blake's pouch cysts and megacisterna magna underwent spontaneous resolution in utero in one third of cases and over 90% of survivors without associated anomalies had normal developmental outcome at 1-5 years. Isolated Dandy-Walker malformation and vermian hypoplasia were associated with normal developmental outcome in only 50% of cases.

CONCLUSION

Prenatal neurosonography and MRI are similarly accurate in the categorization of posterior fossa fluid collections from mid gestation. Blake's pouch cyst and megacisterna magna are risk factors for associated anomalies but when isolated have an excellent prognosis, with a high probability of intrauterine resolution and normal intellectual development in almost all cases. Conversely, Dandy-Walker malformation and vermian hypoplasia, even when they appear isolated antenatally, are associated with an abnormal outcome in half of cases.

Prenatal neurologic anomalies: sonographic diagnosis and treatment

The low prevalence of fetal CNS anomalies results in a restricted level of exposure to, and limited experience for most obstetricians involved in, prenatal ultrasound. Sonographic guidelines for screening the fetal brain in a systematic way may increase the detection rate of fetal CNS anomalies, thus promoting correct referral to tertiary care centers offering patients a multidisciplinary approach to the condition. The aim of this review is to elaborate on the prenatal sonographic diagnosis and outcome of various CNS malformations. Detailed neurosonographic investigation has become available through high-resolution vaginal ultrasound probes and the development of a variety of 3-dimensional (3D) ultrasound modalities, such as ultrasound tomographic imaging. In addition, fetal magnetic resonance imaging is particularly helpful in the detection of gyration and neurulation anomalies, and disorders of the gray and white matter. Isolated mild ventriculomegaly is a rather common finding with good overall outcome. With an increasing diameter of the atria, however, and especially with the presence of associated malformations, long-term neurodevelopmental and behavioral outcome is disturbed in about 15% or more of cases. In view of recent developments in fetal therapy for neural tube defects, there is a clear need for a high level of ultrasound screening, work-up and counseling in tertiary care centers to identify those cases that might benefit from in utero intervention. The failure of prosencephalic midline induction and development results in midline defects ranging from alobar holoprosencephaly to isolated corpus callosum defects. The detection of callosal abnormaties is enhanced by 3D ultrasound, but counseling on neurodevelopmental outcome remains challenging. The Dandy-Walker spectrum includes isolated megacisterna magna, Blake's pouch cyst, hypoplasia of the vermis and Dandy-Walker malformation. Except for complete agenesis of the vermis associated with fourth ventricle cyst formation, data on long-term outcomes for the various conditions is largely lacking. Congenital cytomegalovirus (CMV) results in the highest incidence of children born with, or developing, long-term neurologic conditions. If proof of fetal infection has been delivered, microcephaly, cortical malformations, and intraparenchymal cysts show a strong correlation with poor outcome. Fetuses with CMV-related ultrasound abnormalities might benefit from maternal transplacental treatment. The aneurysm of the vein of Galen, a vascular malformation of the brain, often results in high cardiac output failure. After neonatal arterial embolization, survival is about 50% with normal neurologic development in 36% of cases. Over 50% of intracranial tumors are teratomata, presenting as fast-growing heterogeneous solid-cystic masses with calcifications. Most intracranial hemorrhages are related to the ventricular system, and prognosis is often poor, particularly in cases involving parenchymal and subdural bleeding. Proliferation disorders of the brain are often characterized by microcephaly. Their etiology is heterogeneous and prenatal diagnosis is often made late in gestation.

Contrast ventriculo-cisternography: an auxiliary test for suspected fourth ventricular outlet obstruction

PURPOSE

Fourth ventricular outlet obstruction (FVOO) causes obstructive hydrocephalus. Often, despite high-quality MRI sequences, differentiation between FVOO and communicating (absorptive) hydrocephalus is not easy. We describe our initial experience with five children with suspected FVOO that underwent CT ventriculography (CTV) or cisternography (CTC), to assist with this difficult diagnosis.

METHODS

Over 2.5 years, five children with suspected FVOO (5 months-7.5 years old) underwent CTV or CTC. Technical and clinical data were retrospectively collected.

RESULTS

Four children had progressive macrocephaly, and one child had progressive ventriculomegaly. On CTV/CTC, four of five children showed communication between the ventricular system and spinal subarachnoid space or prepontine cistern, as evidenced by passage of contrast material. One child had a FVOO and therefore underwent an endoscopic third ventriculostomy, and is since, symptom and shunt free for 2.5 years.

CONCLUSION

CT ventriculography in infants, and CT cisternography in elder children, may assist to differentiate between FVOO and communicating hydrocephalus. The importance of these tests is for children with MRI suggestive of FVOO related hydrocephalus, but with no clear demonstration of the obstruction site. The implication of this differentiation may be for deciding between treatment of hydrocephalus with a ventriculoperitoneal shunt or with an endoscopic third ventriculostomy.

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.