Background:In 1900, Joseph Blake described a transient posterior evagination of the tela choroidea of the fourth ventricle in the normal 130-day old human embryo. He was the first to recognize and fully elucidate on the real nature of the foramen of Magendie as an aperture, which develops within a saccular expansion of the embryonic fourth ventricular cavity. The persistence of this temporary fourth ventricular outpouching into the postnatal period and its significance either as separate entity or as an entity within the Dandy–Walker continuum has over the years been one of the most controversial topics in both neurosurgical and neuroradiological literature.Methods:A search of the medical literature was conducted for publications addressing the historical, embryological, and neuororadiological features as well as the clinical presentation and management of persistent Blake's pouch.Results:The literature on the various features of Blake's pouch cyst has limited areas of consensus between various authors.Conclusion:Blake's pouch cyst is a rare entity that is thought to belong to the Dandy–Walker continuum. It has a variable clinical presentation and when symptomatic can be treated with an endoscopic third ventriculostomy or shunting.

Background:Endoscopic biopsy of brain tumors is an important part of the armamentarium of management of intra- and periventricular tumors that is generally considered an acceptable and, in some situations, a preferred method for tissue sampling. The diagnostic yield of the procedure has been variably reported. Technical aspects of the procedure should undoubtedly reflect on its success rate and accuracy. Such impact on diagnostic yield of endoscopic brain biopsy is infrequently discussed in the literature.Methods:A search of the medical literature was conducted for publications on endoscopic brain biopsy. These reports were analyzed regarding the various technical aspects.Results:In the 43 publications analyzed, lenscopes were exclusively used in 22 reports and a tissue diagnosis was possible in 362 out of 387 endoscopic biopsies with a diagnostic yield of 93.54%. Only fiberscopes were used in 8 reports and a tissue diagnosis was possible in 100 out of 132 endoscopic biopsies with a diagnostic yield of 75.76%. The diagnostic yield in the mixed and unspecified groups was 88.95 and 88.04%, respectively. Very few details on the histopathological methods and tumor molecular genetics could be found.Conclusion:Endoscopic biopsy of brain tumors has a higher diagnostic yield when lenscopes are used. Neuronavigation seems to add to the diagnostic accuracy of the procedure. Studies detailing molecular genetic features of biopsied tumors are necessary in the future.

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