[Variation in the dimensions of the cerebellomedullary cistern after ventriculo-cardiac shunting].

Various morphological changes of the skull and brain were observed after surgical treatment for internal hydrocephalus. An interesting variation is described by the authors, at the site of the cisterna magna, the size of which can vary. Generally it is the last one to dilate when an internal hydrocephalus occurs, but it is the first to regress after inserting a drainage of the cerebrospinal fluid. This behavior of the cisterna magna is discussed, illustrated and reviewed in the literature, after presentation of three clinical histories. From a physiopathological point of view the cisterna magna is considered to be an intermediate formation between the ventricular and the subarachnoid systems.