Blake pouch cyst is a cystic appearing structure that represents posterior ballooning of the inferior medullary velum into the cisterna magna, below and posterior to the vermis that communicates with open fourth ventricle.
It may be asymptomatic or it can present
- in children or in adulthood with signs of hydrocephalus (usually headache, vomiting, blurred or double vision)
- late in life or be even asymptomatic, probably due to adequate CSF flow through lateral foramen of Luschka
It is a normal transient structure during embryological development but regresses usually in a period of 5 to 12 weeks of gestation when it starts fenestrating to form the foramen of Magendie (which forms in up to 4th month of gestation).
As it arises from area membranacea posterior it does not involve cerebellum or 4th ventricle malformation, which both arise from area membranacea anterior.
- infravermian cyst that communicates with fourth ventricle
- cyst is smooth with thin walls
- it can impress on medial side of cerebellar tonsils due to size
- cyst does not communicate with the cisterna magna posteriorly
- no vermian hypoplasia or rotation
- usually hydrocephalus of 4th and supratentorial ventricles
- elevation of the tentorium but usually normally positioned torcular
- choroid plexus can extend from 4th ventricle into superior portion of cyst
Treatment and prognosis
Preferable treatment of hydrocephalus is endoscopic third ventriculostomy. Prognosis is good.
- 1. Calabrò F, Arcuri T, Jinkins JR. Blake's pouch cyst: an entity within the Dandy-Walker continuum. Neuroradiology. 2000;42 (4): 290-5. Neuroradiology (link) - Pubmed citation
- 2. Epelman M, Daneman A, Blaser SI et-al. Differential diagnosis of intracranial cystic lesions at head US: correlation with CT and MR imaging. Radiographics. 26 (1): 173-96. doi:10.1148/rg.261055033 - Pubmed citation
- 3. Azab WA, Shohoud SA, Elmansoury TM et-al. Blake's pouch cyst. Surg Neurol Int. 2014;5 (1): 112. doi:10.4103/2152-7806.137533 - Free text at pubmed - Pubmed citation
Synonyms & Alternative Spellings
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