Blake Pouch: It Is Time to Revisit Classical Descriptions on the Development of the Roof of the Fourth Ventricle.

Cystic anomalies of the posterior fossa constitute an important chapter of the malformations of this region. Their interpretation is largely based on the existence of a pouch described by Joseph Blake in 1900. We have reviewed the ancient literature on which this description is based. All human data were obtained from only three fetuses. The histological and embryological analysis of these observations leads us to remain very cautious as to their significance. Indeed, this region of the posterior fossa is very fragile and subject to numerous technical artifacts. In addition, errors in fetal age lead us to believe that one of the observations cannot be used. It is therefore appropriate to be very careful when using this old literature. All these elements justify the need to revisit this problem in order to determine the normal development of this region in humans.