Blake's Pouch Cyst Research Articles

A pathological approach to anomalies of the posterior fossa

Both clinical and postmortem diagnoses of posterior fossa anomalies remain difficult to make and to corroborate. This is particularly true for Dandy-Walker malformation and variant. Difficulties arise for a variety of reasons, including technical and methodological ones, but also because the conditions may overlap anatomically with others, most notably mega cisterna magna, Blake's pouch cyst, and posterior fossa (arachnoid) cysts. Family counseling is difficult and complicated not only by diagnostic uncertainties but by the highly variable prognosis. In this study, a systematic pathologic approach to study of the posterior fossa is put forth. The benefits of postmortem imaging and in situ and ex situ examination of posterior fossa contents are demonstrated. Normative data for cerebellar width (transverse cerebellar diameter) and height and vermian width and height are derived for the fetal period. These data will help workers recognize changes in these structures, particularly hypoplasia. Basic morphologic definitions of posterior fossa anomalies are advanced, in the hopes that better agreement can be reached between clinical and pathologic diagnoses and that better patient and family care will result.

Midline cystic malformations of the brain: imaging diagnosis and classification based on embryologic analysis

This article describes a classification and imaging diagnosis of intracranial midline cystic malformations based on neuroembryologic analysis. Midline cystic malformations are classified into two categories from an embryologic point of view. In one category, the cyst represents expansion of the roof plate of the brain vesicle, and in the other the cyst consists of extraaxial structures such as an arachnoid membrane or migrating ependymal cells. Infratentorial cysts, such as the Dandy-Walker cyst or Blake's pouch cyst, and supratentorial cysts, such as a communicating interhemispheric cyst with callosal agenesis or a dorsal cyst with holoprosencephaly, are included in the first category. Infratentorial arachnoid cavities, such as the arachnoid cyst, arachnoid pouch, and mega cisterna magna, are in the second category. Noncommunicating interhemispheric cysts, such as interhemispheric arachnoid cyst or ependymal cyst, with callosal agenesis are also in the second category. A careful review of embryologic development is essential for understanding these midline cysts and for making a more accurate radiologic diagnosis.

Evaluation of CSF flow patterns of posterior fossa cystic malformations using CSF flow MR imaging

Differential radiologic diagnosis of cystic malformations of the posterior fossa is often difficult with conventional imaging techniques because of overlapping features of these entities. Posterior fossa cystic malformations occupy the cerebrospinal fluid (CSF) spaces. They may create secondary dynamic effects on the movements of CSF. The aim of this study was to investigate CSF flow alterations in posterior fossa cystic malformations with CSF flow MR imaging. The study included 40 patients with cystic malformations of the posterior fossa. The patients underwent cardiac-gated phase-contrast cine MR imaging. CSF flow was qualitatively evaluated using an in-plane phase-contrast sequence in the midsagittal plane. The MR images were displayed in a closed-loop cine format. Twelve of the patients had communicating arachnoid cyst, seven had non-communicating arachnoid cyst, ten had mega cisterna magna, six had Dandy-Walker malformation, two had Dandy-Walker variant, and three had Blake's pouch cyst. CSF flow MR imaging indicated the regions of no, slow or higher flow, direction of flow, and abnormal cystic fluid motion. Each malformation displayed a distinct CSF flow pattern. Phase-contrast cine MR imaging for CSF flow evaluation may be a useful adjunct to routine MR imaging in the evaluation of the cystic malformations of the posterior fossa because it can improve the specificity in differentiating such malformations.

Plea for an anatomical approach to abnormalities of the posterior fossa in prenatal diagnosis

Plea for an anatomical approach to abnormalities of the posterior fossa in prenatal diagnosis

P02.10: The cisterna magna septa—a probable vestigial remnant of the roof of the rhombencephalic vesicle

Linear echoes are often seen in the fetal and neonatal cisterna magna. These lines have been variously described as the straight sinus, the Torcula Herophili, dural folds of the inferior attachments of the falx cerebelli, or bridging arachnoid septations. Through improved knowledge of posterior fossa embryology, anatomy and malformations and our own observations in fetuses and neonates, we believe that these septa represent a remnant of Blake's pouch, a normal dorsal extension of the developing 4th ventricle. We also demonstrate the probable relationship between these septa, the Dandy-Walker continuum, mega cisterna magna and Blake's pouch cyst. The parallel septa consistently observed in the cisterna magna are seen infero-posterior to the cerebellar vermis. The falx cerebelli is visible separately. There is continuity of the parallel septa with the inferior aspect of the fourth ventricle at the caudal aspect of the cerebellar vermis. The CSF space between the cisterna magna septa is in direct continuity with the fourth ventricle. The CSF between the lines is completely anechoic because it is intra-axial. The CSF outside the lines is usually slightly echogenic because it is in the subarachnoid space which is trabeculated by pial extensions. On sagittal views the superior margin of Blake's pouch can be seen separately from the dural fold that forms the inferior margin of the falx cerebelli. Sometimes the lines are bowed outwards giving the impression of a cyst. In light of these observations we propose that it is likely that the cisterna magna septa represent the walls of Blake's pouch, a phylogenetically vestigial structure observed during ontogeny. Additionally our observations support current opinion that Blake's pouch cyst and mega-cisterna magna may represent (less severe) abnormalities within the Dandy-Walker continuum.

Syringomyelia Associated With Hydrocephalus and Blake’s Pouch Cyst

This is a case report of a 37-year-old woman who sought treatment for a large syringomyelic cavitation extending from C3 to the entire medulla, a tetraventricular hydrocephalus, and a cystic cavitation in the posterior cranial fossa communicating with the fourth ventricle (Blake's pouch cyst). The patient underwent a decompressive craniectomy, a C1 laminectomy, and the opening of the cysts to enable communication with the subarachnoid spaces. After an initial period of symptom remission, reassured by the magnetic resonance images indicating a reduction of the syringomyelia, the patient's neurologic conditions deteriorated because of further dilation of the ventricular cavities, which was resolved by the insertion of a ventriculoperitoneal shunt. To suggest the treatment of choice in a patient with syringomyelia and hydrocephalus caused by Blake's pouch cyst. Blake's pouch cyst is an entity often poorly understood, deriving from nonperforation of the primitive foramen of Magendie, causing a precarious equilibrium of the cerebrospinal fluid flow resulting from a defect in communication between the fourth ventricle and the encephalic and spinal subarachnoid spaces. Authors report the association of Blake's pouch cyst with cervicodorsal syringomyelia and tetraventricular hydrocephalus. A case of syringomyelia associated with hydrocephalus and Blake's pouch cyst is described. Symptoms of syringomyelia and hydrocephalus disappeared only after positioning of a ventriculoperitoneal shunt. The treatment of choice for a case of syringomyelia associated with Blake's pouch cyst and hydrocephalus is the application of a ventriculoperitoneal shunt or, even better, an endoscopic third ventriculostomy.

Cystic retrocerebellar malformations: unification of the Dandy-Walker complex and the Blake's pouch cyst.

Twenty-six cases of developmental retrocerebellar cyst (RCC) formation are studied with respect to determining the usefulness and anatomic relevance of separate terms currently in use, including Dandy-Walker complex, Dandy-Walker malformation, Dandy-Walker variant, mega-cisterna magna (MCM), and Blake's pouch cyst. An anatomic and embryological continuum between Dandy-Walker complex and Blake's pouch cyst is proposed. A method for the useful assessment of RCC is outlined. The patency or closure of the aqueduct is crucial to the evaluation and management of hydrocephalus associated with RCC formation.

Posterior Fossa Cysts

The authors studied 19 cases of posterior fossa cysts —14 of retrocerebellar cyst, three of unilateral cerebellar hemispheric cyst, and two of cerebellopontine angle cyst— all of which were presumptively diagnosed by means of axial computed tomography (CT) There were 15 children and four adults, ranging in age from 2.5 months to 65 years. Thirteen were male and six female. The patients underwent various neuroradiological tests, including sagittal reconstruction CT, radioisotope (RI) and/or CT cisternography, and angiography, as appropriate. Seventeen patients were treated surgically by excision of the outer wall of the cyst, followed in 15 cases by cystoperitoneal shunting. Retrospective classification of the 19 cases yielded seven communicating or non-communicating intra-arachnoid cysts, two Blake's pouch cysts, one Dandy-Walker cyst, two Dandy-Walker variants, one glioependymal cyst, one enlarged cisterna magna with communicating hydrocephalus, one fourth ventricular diverticulum, and four cases of large cisterna magna. In 10 of the 17 operated cases, the cyst disappeared, the cerebellum expanded, and the clinical symptoms abated. Four major findings were obtained in this study. First, posterior fossa intra-arachnoid cysts were encountered more frequently than expected and were found to be surgically treatable. Second, although fourth ventricular cysts were categorized as Dandy-Walker cyst, Dandy-Walker variant, and Blake's pouch cyst in this study, the neuroradiological distinctions between these three types are uncertain. Third, the surgical findings did not always corresponded to the preoperative classification. Finally, in cases with the following neuroradiological findings, surgery appears to be indicated: 1) occipital bossing or petrosal scalloping with distortion or obliteration of cerebrospinal fluid (CSF) cisterns of the posterior fossa; 2) compression and deformity of the brain surrounding the cyst; 3) RI and/or CT-cisternographic findings suggestive of disturbance of intracystic CSF circulation; and 4) a non-communicating cyst.